Purpose–The brake pipe system was an essential braking component of the railway freight trains,but the existing E-type sealing rings had problems such as insufficient low-temperature resistance,poor heat stability an...Purpose–The brake pipe system was an essential braking component of the railway freight trains,but the existing E-type sealing rings had problems such as insufficient low-temperature resistance,poor heat stability and short service life.To address these issues,low-phenyl silicone rubber was prepared and tested,and the finite element analysis and experimental studies on the sealing performance of its sealing rings were carried out.Design/methodology/approach–The low-temperature resistance and thermal stability of the prepared lowphenyl silicone rubber were studied using low-temperature tensile testing,differential scanning calorimetry,dynamic thermomechanical analysis and thermogravimetric analysis.The sealing performance of the lowphenyl silicone rubber sealing ring was studied by using finite element analysis software abaqus and experiments.Findings–The prepared low-phenyl silicone rubber sealing ring possessed excellent low-temperature resistance and thermal stability.According to the finite element analysis results,the finish of the flange sealing surface and groove outer edge should be ensured,and extrusion damage should be avoided.The sealing rings were more susceptible to damage in high compression ratio and/or low-temperature environments.When the sealing effect was ensured,a small compression ratio should be selected,and rubbers with hardness and elasticity less affected by temperature should be selected.The prepared low-phenyl silicone rubber sealing ring had zero leakage at both room temperature(RT)and�508C.Originality/value–The innovation of this study is that it provides valuable data and experience for the future development of the sealing rings used in the brake pipe flange joints of the railway freight cars in China.展开更多
BACKGROUND A case study of multiple distinct levels of skipped thoracolumbar spine infection was reported in which 13 successful vacuum sealing drainage(VSD)surgeries were treated.CASE SUMMARY The patient underwent a ...BACKGROUND A case study of multiple distinct levels of skipped thoracolumbar spine infection was reported in which 13 successful vacuum sealing drainage(VSD)surgeries were treated.CASE SUMMARY The patient underwent a total of 13 procedures within our medical facility,including five performed under local anesthesia and eight performed under general anesthesia.The source of the ailment was ultimately identified as Enterobacter cloacae.After the last procedure,the patient's symptoms were alleviated,and the recovery process was satisfactory.Three months post-operation,the Japanese Orthopaedic Association scores had improved to 100%.Imageological examination revealed a satisfactory position of internal fixation,and the abnormal signals in the vertebral body and intervertebral space had been eliminated when compared to the pre-operative results.CONCLUSION The study demonstrates that the extreme lateral approach debridement combined with multiple VSD operations is a secure and successful method of treatment for recurrent spinal infection,providing an alternative to traditional surgery.展开更多
A ternary early-strengthening agent consisting of calcium formate+triethanolamine+lithium sulfate was compounded with quercetin to shorten the setting time of cementitious materials while ensuring their early strength...A ternary early-strengthening agent consisting of calcium formate+triethanolamine+lithium sulfate was compounded with quercetin to shorten the setting time of cementitious materials while ensuring their early strength.The optimum ratio of the three early-strengthening agents was determined as 0.5%calcium formate+0.04%triethanolamine+0.4%lithium sulfate by response surface methodology.The effects of the ternary early-strengthening agent composed of calcium formate+triethanolamine(TEA)+lithium sulfate on cementitious pore sealing materials under the synergistic effect of quercetin were studied by means of the performance tests of compressive strength,fluidity,and setting time,and the microstructural characterizations of X-ray powder diffractometer(XRD),thermogravimetry(TG-DSC)and scanning electron microscopy(SEM).The study shows that the synergistic effect of ternary early-strengthening agent and quercetin forms a multi-performance composite admixture for cementitious materials.The best performance was obtained with the compounding scheme of 0.5%calcium formate+0.04%triethanolamine+0.4%lithium sulfate ternary early-strengthening agent and 0.05%quercetin.The compressive strength of 1,3,7,and 28 d are 94.8%,39.8%,42%,and 28%higher than those of the blank group,respectively.The initial time and final setting time are 41 and 57 minutes,respectively.According to the microscopic analysis,the network and fibrous C-S-H gels generated by ternary early-strengthening agents are attached to the surface promoted by quercetin,which forms skeleton support while thickening and solidifying the cement slurry,which enhances the early compressive strength of the cement-based materials.展开更多
The low-melting glass of Bi2O_(3)-B2O_(3)-SiO_(2)(BiBSi)system was used for the first time for laser sealing of vacuum glazing.Under the condition of constant boron content,how the structure and properties vary with B...The low-melting glass of Bi2O_(3)-B2O_(3)-SiO_(2)(BiBSi)system was used for the first time for laser sealing of vacuum glazing.Under the condition of constant boron content,how the structure and properties vary with Bi/Si ratio in low-melting glass was investigated.In addition,the relationships between laser power,low-melting glass solder with different Bi/Si ratios and laser sealing shear strength were revealed.The results show that a decrease in the Bi/Si ratio can cause a contraction of the glass network of the low-melting glass,leading to an increase of its characteristic temperature and a decrease of its coefficient of thermal expansion.During laser sealing,the copper ions in the low-melting glass play an endothermic role.A change in the Bi/Si ratio will affect the valence state transition of the copper ions in the low-melting glass.The absorbance of the low-melting glass does not follow the expected correlation with the Bi/Si ratio,but shows a linear correlation with the content of divalent copper ions.The greater the concentration of divalent copper ions,the greater the absorbance of the low-melting glass,and the lower the laser power required for laser sealing.The shear strength of the low melting glass solder after laser sealing was tested,and it was found that the maximum shear strength of Z1 glass sample was the highest up to 2.67 MPa.展开更多
In the process of oil and gas production,reservoir pressure depletion leads to changes in pore pressure and in-situ stress in caprock,which may reactivate closed faults in caprock,break the sealing of caprock,and make...In the process of oil and gas production,reservoir pressure depletion leads to changes in pore pressure and in-situ stress in caprock,which may reactivate closed faults in caprock,break the sealing of caprock,and make depleted oil and gas reservoirs unsuitable for gas storage.In order to effectively evaluate the sealing of faults in caprock above depleted reservoir and provide a basis for a reasonable selection of injection time and location for gas storage,this paper comprehensively considers fault slip potential(FSP)and fault tensile potential(FTP),and establishes a fault sealing evaluation model in caprock above depleted reservoir.The influences of distance of fault from reservoir top,reservoir pressure depletion degree,cap mechanical property,fault occurrence,fault frictional property and in-situ stress anisotropy in caprock on different types of FSP and FTP are analyzed.The results show that for normal faults,reverse faults,and strike-slip faults,FTP increases with reservoir depletion and does not cause tensile failure,among which FTP is the smallest for normal faults.FSP is the key to controlling fault sealing in caprock above depleted reservoir.For reverse faults and strike-slip faults,in the early stage of reservoir depletion,the FsP is larger when the fault is farther away from the top of the reservoir,while normal faults are the opposite.When the normal fault is closer to the top of the reservoir,the cap poisson ratio is smaller,the Biot's coefficient is larger,the internal friction coefficient of the fault is smaller,the inherent shear strength of the fault is smaller,σH/σv is smaller,σh/σv is smaller,45°<β<75°,α=0° or α=180°,the FSP is larger with the reservoir depletion,and the shear failure of the fault is the most likely.At this time,the reservoir pressure should be strictly controlled not to be too small,so that it can be suitable for the construction of gas storage.Under other conditions,the possibility of shear failure of the caprock is less.For reverse faults and strike-slip faults,when is smaller,the FSP decreases first and then increases with reservoir depletion.Although the possibility of shear failure decreases in the initial stage of reservoir depletion,it increases in the later stage.The research results can provide a theoretical basis for the reconstruction of underground gas storage.展开更多
A principle was proposed for designing a method to seal anodized aluminum used in semiconductor processing apparatuses.Thermodynamic calculations and Fick’s second law were used to reveal trends in the metal ion depo...A principle was proposed for designing a method to seal anodized aluminum used in semiconductor processing apparatuses.Thermodynamic calculations and Fick’s second law were used to reveal trends in the metal ion deposition,deposition product stability,vapor pressures of halides for selected metal ions,the holding temperature,and time.Interactions between ion concentrations and the sealing temperature were also revealed.According to the design principles,anodized aluminum dipped in 1 mM Cr^(3+)ion solution and steam-sealed for 18 h exhibited the highest corrosion resistance when exposed to 5 wt.%HCl solution and HCl gas,verifying the designed results.展开更多
BACKGROUND The current method of cleaning and changing dressings for non-healing lumbar incisions post-radiotherapy is time-consuming and laborious,with very poor results.We here report a patient with radiation dermat...BACKGROUND The current method of cleaning and changing dressings for non-healing lumbar incisions post-radiotherapy is time-consuming and laborious,with very poor results.We here report a patient with radiation dermatitis who developed a nonhealing wound after lumbar spinal surgery.The wound was successfully treated with vacuum sealing drainage therapy,confirming its feasibility in complex wound healing.CASE SUMMARY The patient was a 76-year-old female with lung cancer,positron emission tomography/computed tomography showed bone metastasis in L2 and L3 vertebrae.After 2 months of local radiotherapy to the lumbar spine,symptoms did not improve and pain worsened.She had lumbar lesion clearance and internal fixation surgery,but developed a nonhealing wound of approximately 15 cm postoperatively.After 12 rounds of clearing necrotic and unhealthy tissue,78 days of negative pressure therapy promoted granulation tissue growth and wound healing,resulting in wound healing.CONCLUSION Vacuum sealing drainage therapy has shown efficacy in treating nonhealing wounds after radiotherapy,promoting wound healing and reducing infection risk.展开更多
Pipeline Inspection Gauge(pig)is an important equipment for oil and gas pipelines during different stages of their operations to perform functions such as dewatering,cleaning,and inspection.Owing to the hyperelasticit...Pipeline Inspection Gauge(pig)is an important equipment for oil and gas pipelines during different stages of their operations to perform functions such as dewatering,cleaning,and inspection.Owing to the hyperelasticity,time and temperature-dependent material behaviour of the sealing disc attached on the pig,the contact between the pig and the pipeline expresses complex behaviour,leading to an uncertainty in the prediction of the pig's frictional force.Knowing the deformation of the sealing discs well is essential and can be highly meaningful for predicting the pig motion,as well as reducing the pigging risks.In this study,the geometrical deformation of the sealing discs with different sizes are investigated through experiments and numerical simulations.The effects of the four nondimensionalized parameters(interference,thickness per pipeline inner diameter,and clamping ratio)of the sealing discs on the deformation behaviour were observed and discussed,and an improved mathematical model for predicting the geometrical deformation of the sealing discs was proposed and verified.With the auxiliary angleαadded in the improved mathematical model,the relative error declines to 1.87%and 3.18%respectively for predicting deformation of the sealing discs in size of 2-inch and 40-inch pig.The results of this study can help better understand the frictional force of a pig with sealing discs,as well as its motion.展开更多
The cyclic injection and production of fluids into and from underground gas storage(UGS)may lead to caprock failure,such as capillary sealing failure,hydraulic fracturing,shear failure,and fault slipping or dilation.T...The cyclic injection and production of fluids into and from underground gas storage(UGS)may lead to caprock failure,such as capillary sealing failure,hydraulic fracturing,shear failure,and fault slipping or dilation.The dynamic sealing capacity of a caprock-fault system is a critical constraint for safe operation,and is a key factor in determining the maximum operating pressure(MOP).This study proposed an efficient semi-analytical method for calculating changes in the in situ stress within the caprock.Next,the parameters of dynamic pore pressure,in situ stresses,and deformations obtained from reservoir simulations and geomechanical modeling were used for inputs for the analytical solution.Based on the calculated results,an experimental scheme for the coupled cyclic stress-permeability testing of caprock was designed.The stability analysis indicated that the caprock was not prone to fatigue shear failure under the current injection and production strategy,supported by the experimental results.The experimental results further reveal that the sealing capacity of caprock plugs may remain stable.This phenomenon is attributed to cyclic stress causing pore connectivity and microcrack initiation in certain plugs,while leading to pore compaction in others.A comparison between the dynamic pore pressure and the minimum principal stress suggests that the risk of tensile failure is extremely low.Furthermore,although the faults remain stable under the current injection and production strategies,the continuous increase in injection pressure may lead to an increased tendency for fault slip and dilation,which can cause fault slip ultimately.The MOPs corresponding to each failure mode were calculated.The minimum value of approximately 36.5 MPa at capillary sealing failure indicated that the gas breakthrough in the caprock occurred earlier than rock failure.Therefore,this minimumvalue can be used as the MOP for the target UGS.展开更多
Fluid channeling caused by seal failure at the cement sheath-formation interface during fracturing is a severe problem in oil gas wells.In this study,a novel model was developed to evaluate interface sealing integrity...Fluid channeling caused by seal failure at the cement sheath-formation interface during fracturing is a severe problem in oil gas wells.In this study,a novel model was developed to evaluate interface sealing integrity.The model's accuracy was verified based on a self-developed interface seal evaluation device and an experiment.Subsequently,the interface seal under different formation conditions was investigated using this model.The theoretical calculation showed that for a cement sheath-carbonate formation interface,the channeling of acid-fracturing fluid caused interface seal failure and sustained casing pressure in the annulus space between the technical casing and formation.Mutual channeling between the fracturing sections occurred at the cement sheathshale formation interface during fracturing.For a sandstone formation,the interface seal failure caused the channeling between a water-bearing formation and a sandstone formation.Aiming at different formation conditions,the mechanical properties requirements of Young's modulus and Poisson's ratio of cement sheath were proposed respectively to ensure its seal integrity.The proposed model and method can be used to evaluate and optimize sealing integrity during fracturing.展开更多
Hardfacing of valve sealings in power plants with Inconel 625 alloy has been reviewed in this paper.The overlaying processes,over-lay microstructures,and weldability issues during the hardfacing process have been anal...Hardfacing of valve sealings in power plants with Inconel 625 alloy has been reviewed in this paper.The overlaying processes,over-lay microstructures,and weldability issues during the hardfacing process have been analyzed.The results indicate that almost all melting welding processes can be used for hardfacing of Inconel 625 alloy.During hardfacing,it is necessary to strictly control the penetration,reduce the overlay dilution rate,so as to prevent the formation of partially mixed zone(PMZ)and solidification crack.From the perspective of controlling the penetration,reducing the overlay dilution rate,and automated hardfacing,the most suitable process for hardfacing Inconel 625 alloy on the valve sealings in power plants is cold metal transfer(CMT)welding process.展开更多
In petroleum extraction,the sealing surfaces of bolted joints are susceptible to damage due to the high-temperature and high-pressure conditions in wellbores.This damage adversely affects sealing performance,consequen...In petroleum extraction,the sealing surfaces of bolted joints are susceptible to damage due to the high-temperature and high-pressure conditions in wellbores.This damage adversely affects sealing performance,consequently leading to the failure and damage of threaded connections.In severe cases,it can result in considerable economic losses and trigger safety accidents.The sealing performance of special bolted joints holds crucial importance for production efficiency,output,equipment lifespan,and cost control.Enhancing the sealing perfor-mance of threaded connections can have a positive impact on industrial production and environmental protection.The existing research on American Petroleum Institute threaded joints has been thorough and has obtained a series of excellent results.However,the research on the sealing damage mechanism of threaded connections under complex well conditions lacks sufficient depth and that on new sealing technology is scarce.This study proposes a half-size evaluation test to address the abovementioned problem.Based on this test,an investigation into the sealing performance of threaded connections under high-temperature,cyclic loading,and high-temperature creep conditions is conducted.This study uses a combined approach of finite element methods and experiments to investigate the impact of different makeup torques on the sealing performance of premium threaded connections(PTCs).The results of the half-size evaluation test indicate that temperature notably influences the sealing performance of threaded connections.The continuous action of high temperatures causes contact pressure and sealing performance to decrease,and sealing contact pressure increases after cooling.Finite element and test results show that for a certain joint A,the greater the torque,the higher the critical sealing pressure of the thread,and the better the sealing performance.The research on the sealing damage mechanism of PTCs provides a scientific basis and theoretical guidance for the further optimization and development of PTCs.展开更多
Manufacturers must identify and classify various defects in automotive sealing rings to ensure product quality.Deep learning algorithms show promise in this field,but challenges remain,especially in detecting small-sc...Manufacturers must identify and classify various defects in automotive sealing rings to ensure product quality.Deep learning algorithms show promise in this field,but challenges remain,especially in detecting small-scale defects under harsh industrial conditions with multimodal data.This paper proposes an enhanced version of You Only Look Once(YOLO)v8 for improved defect detection in automotive sealing rings.We introduce the Multi-scale Adaptive Feature Extraction(MAFE)module,which integrates Deformable ConvolutionalNetwork(DCN)and Spaceto-Depth(SPD)operations.This module effectively captures long-range dependencies,enhances spatial aggregation,and minimizes information loss of small objects during feature extraction.Furthermore,we introduce the Blur-Aware Wasserstein Distance(BAWD)loss function,which improves regression accuracy and detection capabilities for small object anchor boxes,particularly in scenarios involving defocus blur.Additionally,we have constructed a high-quality dataset of automotive sealing ring defects,providing a valuable resource for evaluating defect detection methods.Experimental results demonstrate our method’s high performance,achieving 98.30% precision,96.62% recall,and an inference speed of 20.3 ms.展开更多
Dear Editor,We report a surgical method for treating repeat Descemet’s membrane(DM)detachments in two cases with DM micro-perforation during deep anterior lamellar keratoplasty(DALK).DM micro-perforation is a common ...Dear Editor,We report a surgical method for treating repeat Descemet’s membrane(DM)detachments in two cases with DM micro-perforation during deep anterior lamellar keratoplasty(DALK).DM micro-perforation is a common intraoperative complication that occurs during the performance of DM baring in DALK,using methods such as the bigbubble air technique[1].The sequelae of DM micro-perforations include postoperative DM detachments,higher endothelial cell loss,endothelial decompensation,and transplant interface scarring[2].展开更多
A rotary sealing device that automatically compensates for wear is designed to address the issues of easy wear and the short service life of the rotary sealing device with automatic wear compensation in mining machine...A rotary sealing device that automatically compensates for wear is designed to address the issues of easy wear and the short service life of the rotary sealing device with automatic wear compensation in mining machinery.After the end face of the guide sleeve wears out,it still tightly adheres to the sealing valve seat under the pressure difference,achieving automatic wear compensation.Based on fluid-solid coupling technology,the structural strength of the rotary sealing device was checked.The influence of factors on the sealing performance of rotary sealing devices was studied using the control variable method.The results show that as the pressure of water increases,the leakage rate of the sealing device decreases,and after 30 MPa,the leakage rate is almost 0 mL/h.The temperature of the rotating sealing device increases with the increase of rotation speed or pressure,and the temperature is more affected by the rotation speed factor.The frictional torque increases with increasing pressure and is independent of rotational speed.Comprehensive analysis shows that the wear resistance and reliability level of the sealing guide sleeve material is PVDF>PEEK>PE>PA.This study designs a high-pressure automatic compensation wear rotary sealing device and selects the optimal sealing material,providing technical support for the application of high-pressure water jet in mining machinery.展开更多
The nitrile butadiene rubber(NBR)hardness effect on the sealing characteristics of hydraulic O-ring rod seals is analyzed based on a mixed lubrication elastohydrodynamic model.Parameterized studies are conducted to re...The nitrile butadiene rubber(NBR)hardness effect on the sealing characteristics of hydraulic O-ring rod seals is analyzed based on a mixed lubrication elastohydrodynamic model.Parameterized studies are conducted to reveal the mechanism of the influence of rubber hardness on the static and dynamic behavior of seals.The optimized selections of rubber hardness are then investigated under different conditions.Results show that the low hardness seal is prone to stress concentration due to the extrusion effect under high pressure conditions;it is also more prone to leaking.A high hardness seal can better prevent leakage by reducing film thickness but it will cause large frictional power loss and increase the probability of wear failure.The choice of low hardness is recommended to reduce friction with the premise that leakage requirements are met.展开更多
The static sealing of underground gas storage(UGS),including the integrity of cap rocks and the stability of faults,is analyzed from a macro perspective using a comprehensive geological evaluation method.Changes in po...The static sealing of underground gas storage(UGS),including the integrity of cap rocks and the stability of faults,is analyzed from a macro perspective using a comprehensive geological evaluation method.Changes in pore structure,permeability,and mechanical strength of cap rocks under cyclic loads may impact the rock sealing integrity during the injection and recovery phases of UGS.In this work,the mechanical deformation and failure tests of rocks,as well as rock damage tests under alternating loads,are conducted to analyze the changes in the strength and permeability of rocks under multiple-cycle intense injection and recovery of UGS.Additionally,this study proposes an evaluation method for the dynamic sealing performance of UGS cap rocks under multi-cycle alternating loads.The findings suggest that the failure strength(70%)can be used as the critical value for rock failure,thus providing theoretical support for determining the upper limit of operating pressure and the number of injection-recovery cycles for the safe operation of a UGS system.展开更多
Evaluating underground gas storage(UGS)sealing capacity is essential for its safe construction and operational efficiency.This involves evaluating both the static sealing capacity of traps during hydrocarbon accumulat...Evaluating underground gas storage(UGS)sealing capacity is essential for its safe construction and operational efficiency.This involves evaluating both the static sealing capacity of traps during hydrocarbon accumulation and the dynamic sealing capacity of UGS under intensive gas injection and withdrawal,and alternating loads.This study detailed the methodology developed by Sinopec.The approach merges disciplines like geology,geomechanics,and hydrodynamics,employing both dynamic-static and qualitative-quantitative analyses.Sinopec's evaluation methods,grounded in the in situ stress analysis,include mechanistic studies,laboratory tests,geological surveys,stress analysis,and fluid-solid interactions.Through tests on the static and dynamic sealing capacity of UGS,alongside investigations into sealing mechanisms and the geological and geomechanical properties of cap rocks and faults,A geomechanics-rock damage-seepage mechanics dynamic coupling analysis method has been developed to predict in situ stress variations relative to pore pressure changes during UGS operations and evaluate fault sealing capacity and cap rock integrity,thereby setting the maximum operational pressures.Utilizing this evaluation technique,Sinopec has defined performance metrics and criteria for evaluating the sealing capacity of depleted gas reservoirs,enabling preliminary sealing capacity evaluations at UGS sites.These evaluations have significantly informed the design of UGS construction schemes and the evaluation of fault sealing capacity and cap rock integrity during UGS operations.展开更多
Gypsum caprocks'sealing ability is affected by temperature-pressure coupling.Due to the limitations of experimental conditions,there is still a lack of triaxial stress-strain experiments that simultaneously consid...Gypsum caprocks'sealing ability is affected by temperature-pressure coupling.Due to the limitations of experimental conditions,there is still a lack of triaxial stress-strain experiments that simultaneously consider changes in temperature and pressure conditions,which limits the accuracy of the comprehensive evaluation of the brittle plastic evolution and sealing ability of gypsum rocks using temperature pressure coupling.Triaxial stress-strain tests were utilized to investigate the differences in the evolution of the confinement capacity of gypsum rocks under coupled temperaturepressure action and isothermal-variable pressure action on the basis of sample feasibility analysis.According to research,the gypsum rock's peak and residual strengths decrease under simultaneous increases in temperature and pressure over isothermal pressurization experimental conditions,and it becomes more ductile.This reduces the amount of time it takes for the rock to transition from brittle to plastic.When temperature is taken into account,both the brittle–plastic transformation's depth limit and the lithological transformation of gypsum rocks become shallower,and the evolution of gypsum rocks under variable temperature and pressure conditions is more complicated than that under isothermal pressurization.The sealing ability under the temperature-pressure coupling is more in line with the actual geological context when the application results of the Well#ZS5 are compared.This provides a theoretical basis for precisely determining the process of hydrocarbon accumulation and explains why the early hydrocarbon were not well preserved.展开更多
Lost circulation is a common downhole problem of drilling in geothermal and high-temperature,high-pressure(HTHP)formations.Lost circulation material(LCM)is a regular preventive and remedial measure for lost circulatio...Lost circulation is a common downhole problem of drilling in geothermal and high-temperature,high-pressure(HTHP)formations.Lost circulation material(LCM)is a regular preventive and remedial measure for lost circulation.However,conventional LCMs seem ineffective in high-temperature formations.This may be due to the changes in the mechanical properties of LCMs and their sealing performance under high-temperature conditions.To understand how high temperature affects the fracture sealing performance of LCMs,we developed a coupled computational fluid dynamics-discrete element method(CFD-DEM)model to simulate the behavior of granular LCMs in fractures.We summarized the literature on the effects of high temperature on the mechanical properties of LCMs and the rheological properties of drilling fluid.We conducted sensitivity analyses to investigate how changing LCM slurry properties affected the fracture sealing efficiency at increasing temperatures.The results show that high temperature reduces the size,strength,and friction coefficient of LCMs as well as the drilling fluid viscosity.Smaller,softer,and less frictional LCM particles have lower bridging probability and slower bridging initiation.Smaller particles tend to form dual-particle bridges rather than single-particle bridges.These result in a deeper,tighter,but unstable sealing zone.Reduced drilling fluid viscosity leads to faster and shallower sealing zones.展开更多
基金supported by the Science and Technology Research and Development Plan of the China State Railway Group Company Limited(No.Q2023J012).
文摘Purpose–The brake pipe system was an essential braking component of the railway freight trains,but the existing E-type sealing rings had problems such as insufficient low-temperature resistance,poor heat stability and short service life.To address these issues,low-phenyl silicone rubber was prepared and tested,and the finite element analysis and experimental studies on the sealing performance of its sealing rings were carried out.Design/methodology/approach–The low-temperature resistance and thermal stability of the prepared lowphenyl silicone rubber were studied using low-temperature tensile testing,differential scanning calorimetry,dynamic thermomechanical analysis and thermogravimetric analysis.The sealing performance of the lowphenyl silicone rubber sealing ring was studied by using finite element analysis software abaqus and experiments.Findings–The prepared low-phenyl silicone rubber sealing ring possessed excellent low-temperature resistance and thermal stability.According to the finite element analysis results,the finish of the flange sealing surface and groove outer edge should be ensured,and extrusion damage should be avoided.The sealing rings were more susceptible to damage in high compression ratio and/or low-temperature environments.When the sealing effect was ensured,a small compression ratio should be selected,and rubbers with hardness and elasticity less affected by temperature should be selected.The prepared low-phenyl silicone rubber sealing ring had zero leakage at both room temperature(RT)and�508C.Originality/value–The innovation of this study is that it provides valuable data and experience for the future development of the sealing rings used in the brake pipe flange joints of the railway freight cars in China.
基金Supported by Natural Science Foundation of Shandong Province,No.ZR2023MH331.
文摘BACKGROUND A case study of multiple distinct levels of skipped thoracolumbar spine infection was reported in which 13 successful vacuum sealing drainage(VSD)surgeries were treated.CASE SUMMARY The patient underwent a total of 13 procedures within our medical facility,including five performed under local anesthesia and eight performed under general anesthesia.The source of the ailment was ultimately identified as Enterobacter cloacae.After the last procedure,the patient's symptoms were alleviated,and the recovery process was satisfactory.Three months post-operation,the Japanese Orthopaedic Association scores had improved to 100%.Imageological examination revealed a satisfactory position of internal fixation,and the abnormal signals in the vertebral body and intervertebral space had been eliminated when compared to the pre-operative results.CONCLUSION The study demonstrates that the extreme lateral approach debridement combined with multiple VSD operations is a secure and successful method of treatment for recurrent spinal infection,providing an alternative to traditional surgery.
基金Funded by the Key Technologies Research and Development Program(No.2021YFC28000900)the National Natural Science Foundation of China(No.52374178)the Collaborative Innovation Project of Colleges and Universities of Anhui Province(No.GXXT-2020-057)。
文摘A ternary early-strengthening agent consisting of calcium formate+triethanolamine+lithium sulfate was compounded with quercetin to shorten the setting time of cementitious materials while ensuring their early strength.The optimum ratio of the three early-strengthening agents was determined as 0.5%calcium formate+0.04%triethanolamine+0.4%lithium sulfate by response surface methodology.The effects of the ternary early-strengthening agent composed of calcium formate+triethanolamine(TEA)+lithium sulfate on cementitious pore sealing materials under the synergistic effect of quercetin were studied by means of the performance tests of compressive strength,fluidity,and setting time,and the microstructural characterizations of X-ray powder diffractometer(XRD),thermogravimetry(TG-DSC)and scanning electron microscopy(SEM).The study shows that the synergistic effect of ternary early-strengthening agent and quercetin forms a multi-performance composite admixture for cementitious materials.The best performance was obtained with the compounding scheme of 0.5%calcium formate+0.04%triethanolamine+0.4%lithium sulfate ternary early-strengthening agent and 0.05%quercetin.The compressive strength of 1,3,7,and 28 d are 94.8%,39.8%,42%,and 28%higher than those of the blank group,respectively.The initial time and final setting time are 41 and 57 minutes,respectively.According to the microscopic analysis,the network and fibrous C-S-H gels generated by ternary early-strengthening agents are attached to the surface promoted by quercetin,which forms skeleton support while thickening and solidifying the cement slurry,which enhances the early compressive strength of the cement-based materials.
基金Funded by the National Natural Science Foundation of China(No.52472012)Opening Project of State Silica-Based Materials Laboratory of Anhui Province(No.2022KF11)the Research and Development of Glass Powder for Laser Sealing and Its Sealing Technology(No.K24556)。
文摘The low-melting glass of Bi2O_(3)-B2O_(3)-SiO_(2)(BiBSi)system was used for the first time for laser sealing of vacuum glazing.Under the condition of constant boron content,how the structure and properties vary with Bi/Si ratio in low-melting glass was investigated.In addition,the relationships between laser power,low-melting glass solder with different Bi/Si ratios and laser sealing shear strength were revealed.The results show that a decrease in the Bi/Si ratio can cause a contraction of the glass network of the low-melting glass,leading to an increase of its characteristic temperature and a decrease of its coefficient of thermal expansion.During laser sealing,the copper ions in the low-melting glass play an endothermic role.A change in the Bi/Si ratio will affect the valence state transition of the copper ions in the low-melting glass.The absorbance of the low-melting glass does not follow the expected correlation with the Bi/Si ratio,but shows a linear correlation with the content of divalent copper ions.The greater the concentration of divalent copper ions,the greater the absorbance of the low-melting glass,and the lower the laser power required for laser sealing.The shear strength of the low melting glass solder after laser sealing was tested,and it was found that the maximum shear strength of Z1 glass sample was the highest up to 2.67 MPa.
基金National Natural Science Foundation of China(52074224)Key Research and Development Program of Shaanxi Province(2023-YBGY-312).
文摘In the process of oil and gas production,reservoir pressure depletion leads to changes in pore pressure and in-situ stress in caprock,which may reactivate closed faults in caprock,break the sealing of caprock,and make depleted oil and gas reservoirs unsuitable for gas storage.In order to effectively evaluate the sealing of faults in caprock above depleted reservoir and provide a basis for a reasonable selection of injection time and location for gas storage,this paper comprehensively considers fault slip potential(FSP)and fault tensile potential(FTP),and establishes a fault sealing evaluation model in caprock above depleted reservoir.The influences of distance of fault from reservoir top,reservoir pressure depletion degree,cap mechanical property,fault occurrence,fault frictional property and in-situ stress anisotropy in caprock on different types of FSP and FTP are analyzed.The results show that for normal faults,reverse faults,and strike-slip faults,FTP increases with reservoir depletion and does not cause tensile failure,among which FTP is the smallest for normal faults.FSP is the key to controlling fault sealing in caprock above depleted reservoir.For reverse faults and strike-slip faults,in the early stage of reservoir depletion,the FsP is larger when the fault is farther away from the top of the reservoir,while normal faults are the opposite.When the normal fault is closer to the top of the reservoir,the cap poisson ratio is smaller,the Biot's coefficient is larger,the internal friction coefficient of the fault is smaller,the inherent shear strength of the fault is smaller,σH/σv is smaller,σh/σv is smaller,45°<β<75°,α=0° or α=180°,the FSP is larger with the reservoir depletion,and the shear failure of the fault is the most likely.At this time,the reservoir pressure should be strictly controlled not to be too small,so that it can be suitable for the construction of gas storage.Under other conditions,the possibility of shear failure of the caprock is less.For reverse faults and strike-slip faults,when is smaller,the FSP decreases first and then increases with reservoir depletion.Although the possibility of shear failure decreases in the initial stage of reservoir depletion,it increases in the later stage.The research results can provide a theoretical basis for the reconstruction of underground gas storage.
基金supported by the Program of the National Natural Science Foundation of China(Grant No.52371055)the Young Elite Scientist Sponsorship Program Cast(Grant No.YESS20200139)+1 种基金the Basic Scientific Research Project of Liaoning Provincial Department of Education(Grant No.JYTMS20230618)Special thanks are due to the instrumental analysis from the Analytical and Testing Centre,Northeastern University.
文摘A principle was proposed for designing a method to seal anodized aluminum used in semiconductor processing apparatuses.Thermodynamic calculations and Fick’s second law were used to reveal trends in the metal ion deposition,deposition product stability,vapor pressures of halides for selected metal ions,the holding temperature,and time.Interactions between ion concentrations and the sealing temperature were also revealed.According to the design principles,anodized aluminum dipped in 1 mM Cr^(3+)ion solution and steam-sealed for 18 h exhibited the highest corrosion resistance when exposed to 5 wt.%HCl solution and HCl gas,verifying the designed results.
文摘BACKGROUND The current method of cleaning and changing dressings for non-healing lumbar incisions post-radiotherapy is time-consuming and laborious,with very poor results.We here report a patient with radiation dermatitis who developed a nonhealing wound after lumbar spinal surgery.The wound was successfully treated with vacuum sealing drainage therapy,confirming its feasibility in complex wound healing.CASE SUMMARY The patient was a 76-year-old female with lung cancer,positron emission tomography/computed tomography showed bone metastasis in L2 and L3 vertebrae.After 2 months of local radiotherapy to the lumbar spine,symptoms did not improve and pain worsened.She had lumbar lesion clearance and internal fixation surgery,but developed a nonhealing wound of approximately 15 cm postoperatively.After 12 rounds of clearing necrotic and unhealthy tissue,78 days of negative pressure therapy promoted granulation tissue growth and wound healing,resulting in wound healing.CONCLUSION Vacuum sealing drainage therapy has shown efficacy in treating nonhealing wounds after radiotherapy,promoting wound healing and reducing infection risk.
基金supported by Key Technologies Research and Development Program(Grant No.SQ2022YFC2806103)and the National Natural Science Foundation of China(Grant No.51509259).
文摘Pipeline Inspection Gauge(pig)is an important equipment for oil and gas pipelines during different stages of their operations to perform functions such as dewatering,cleaning,and inspection.Owing to the hyperelasticity,time and temperature-dependent material behaviour of the sealing disc attached on the pig,the contact between the pig and the pipeline expresses complex behaviour,leading to an uncertainty in the prediction of the pig's frictional force.Knowing the deformation of the sealing discs well is essential and can be highly meaningful for predicting the pig motion,as well as reducing the pigging risks.In this study,the geometrical deformation of the sealing discs with different sizes are investigated through experiments and numerical simulations.The effects of the four nondimensionalized parameters(interference,thickness per pipeline inner diameter,and clamping ratio)of the sealing discs on the deformation behaviour were observed and discussed,and an improved mathematical model for predicting the geometrical deformation of the sealing discs was proposed and verified.With the auxiliary angleαadded in the improved mathematical model,the relative error declines to 1.87%and 3.18%respectively for predicting deformation of the sealing discs in size of 2-inch and 40-inch pig.The results of this study can help better understand the frictional force of a pig with sealing discs,as well as its motion.
基金supported by the National Natural Science Foundation of China(Grant No.42072166)Natural Science Foundation of Heilongjiang Province of China(Grant No.LH2020D004)Key R&D Program of Heilongjiang Province of China(Grant No.JD2023SJ26)。
文摘The cyclic injection and production of fluids into and from underground gas storage(UGS)may lead to caprock failure,such as capillary sealing failure,hydraulic fracturing,shear failure,and fault slipping or dilation.The dynamic sealing capacity of a caprock-fault system is a critical constraint for safe operation,and is a key factor in determining the maximum operating pressure(MOP).This study proposed an efficient semi-analytical method for calculating changes in the in situ stress within the caprock.Next,the parameters of dynamic pore pressure,in situ stresses,and deformations obtained from reservoir simulations and geomechanical modeling were used for inputs for the analytical solution.Based on the calculated results,an experimental scheme for the coupled cyclic stress-permeability testing of caprock was designed.The stability analysis indicated that the caprock was not prone to fatigue shear failure under the current injection and production strategy,supported by the experimental results.The experimental results further reveal that the sealing capacity of caprock plugs may remain stable.This phenomenon is attributed to cyclic stress causing pore connectivity and microcrack initiation in certain plugs,while leading to pore compaction in others.A comparison between the dynamic pore pressure and the minimum principal stress suggests that the risk of tensile failure is extremely low.Furthermore,although the faults remain stable under the current injection and production strategies,the continuous increase in injection pressure may lead to an increased tendency for fault slip and dilation,which can cause fault slip ultimately.The MOPs corresponding to each failure mode were calculated.The minimum value of approximately 36.5 MPa at capillary sealing failure indicated that the gas breakthrough in the caprock occurred earlier than rock failure.Therefore,this minimumvalue can be used as the MOP for the target UGS.
基金the financial support provide by the National Natural Science Foundation of China(No.52304009)the Natural Science Foundation of Sichuan(No.2023NSFSC0927)the Sichuan Province Innovative Talent Funding Project for Postdoctoral Fellows(No.BX202305)。
文摘Fluid channeling caused by seal failure at the cement sheath-formation interface during fracturing is a severe problem in oil gas wells.In this study,a novel model was developed to evaluate interface sealing integrity.The model's accuracy was verified based on a self-developed interface seal evaluation device and an experiment.Subsequently,the interface seal under different formation conditions was investigated using this model.The theoretical calculation showed that for a cement sheath-carbonate formation interface,the channeling of acid-fracturing fluid caused interface seal failure and sustained casing pressure in the annulus space between the technical casing and formation.Mutual channeling between the fracturing sections occurred at the cement sheathshale formation interface during fracturing.For a sandstone formation,the interface seal failure caused the channeling between a water-bearing formation and a sandstone formation.Aiming at different formation conditions,the mechanical properties requirements of Young's modulus and Poisson's ratio of cement sheath were proposed respectively to ensure its seal integrity.The proposed model and method can be used to evaluate and optimize sealing integrity during fracturing.
文摘Hardfacing of valve sealings in power plants with Inconel 625 alloy has been reviewed in this paper.The overlaying processes,over-lay microstructures,and weldability issues during the hardfacing process have been analyzed.The results indicate that almost all melting welding processes can be used for hardfacing of Inconel 625 alloy.During hardfacing,it is necessary to strictly control the penetration,reduce the overlay dilution rate,so as to prevent the formation of partially mixed zone(PMZ)and solidification crack.From the perspective of controlling the penetration,reducing the overlay dilution rate,and automated hardfacing,the most suitable process for hardfacing Inconel 625 alloy on the valve sealings in power plants is cold metal transfer(CMT)welding process.
文摘In petroleum extraction,the sealing surfaces of bolted joints are susceptible to damage due to the high-temperature and high-pressure conditions in wellbores.This damage adversely affects sealing performance,consequently leading to the failure and damage of threaded connections.In severe cases,it can result in considerable economic losses and trigger safety accidents.The sealing performance of special bolted joints holds crucial importance for production efficiency,output,equipment lifespan,and cost control.Enhancing the sealing perfor-mance of threaded connections can have a positive impact on industrial production and environmental protection.The existing research on American Petroleum Institute threaded joints has been thorough and has obtained a series of excellent results.However,the research on the sealing damage mechanism of threaded connections under complex well conditions lacks sufficient depth and that on new sealing technology is scarce.This study proposes a half-size evaluation test to address the abovementioned problem.Based on this test,an investigation into the sealing performance of threaded connections under high-temperature,cyclic loading,and high-temperature creep conditions is conducted.This study uses a combined approach of finite element methods and experiments to investigate the impact of different makeup torques on the sealing performance of premium threaded connections(PTCs).The results of the half-size evaluation test indicate that temperature notably influences the sealing performance of threaded connections.The continuous action of high temperatures causes contact pressure and sealing performance to decrease,and sealing contact pressure increases after cooling.Finite element and test results show that for a certain joint A,the greater the torque,the higher the critical sealing pressure of the thread,and the better the sealing performance.The research on the sealing damage mechanism of PTCs provides a scientific basis and theoretical guidance for the further optimization and development of PTCs.
文摘Manufacturers must identify and classify various defects in automotive sealing rings to ensure product quality.Deep learning algorithms show promise in this field,but challenges remain,especially in detecting small-scale defects under harsh industrial conditions with multimodal data.This paper proposes an enhanced version of You Only Look Once(YOLO)v8 for improved defect detection in automotive sealing rings.We introduce the Multi-scale Adaptive Feature Extraction(MAFE)module,which integrates Deformable ConvolutionalNetwork(DCN)and Spaceto-Depth(SPD)operations.This module effectively captures long-range dependencies,enhances spatial aggregation,and minimizes information loss of small objects during feature extraction.Furthermore,we introduce the Blur-Aware Wasserstein Distance(BAWD)loss function,which improves regression accuracy and detection capabilities for small object anchor boxes,particularly in scenarios involving defocus blur.Additionally,we have constructed a high-quality dataset of automotive sealing ring defects,providing a valuable resource for evaluating defect detection methods.Experimental results demonstrate our method’s high performance,achieving 98.30% precision,96.62% recall,and an inference speed of 20.3 ms.
基金Supported by Guangdong Basic Research Center of Excellence for Major Blinding Eye Diseases Prevention and Treatment(No.2024-YXGG-016).
文摘Dear Editor,We report a surgical method for treating repeat Descemet’s membrane(DM)detachments in two cases with DM micro-perforation during deep anterior lamellar keratoplasty(DALK).DM micro-perforation is a common intraoperative complication that occurs during the performance of DM baring in DALK,using methods such as the bigbubble air technique[1].The sequelae of DM micro-perforations include postoperative DM detachments,higher endothelial cell loss,endothelial decompensation,and transplant interface scarring[2].
基金Supported by Jiangsu Provincial Natural Science Foundation(Grant No.BK20231497)Jiangsu Provincial Post graduate Research&Practice Innovation Program(Grant No.KYCX25_2982)+3 种基金China University of Mining and Technology Graduate Innovation Program(Grant No.2025WLKXJ094)National Natural Science Foundation of China(Grant No.51975573)National Key R&D Program of China(Grant No.2022YFC2905600)Priority Academic Program Development of Jiangsu Higher Education Institute of China.
文摘A rotary sealing device that automatically compensates for wear is designed to address the issues of easy wear and the short service life of the rotary sealing device with automatic wear compensation in mining machinery.After the end face of the guide sleeve wears out,it still tightly adheres to the sealing valve seat under the pressure difference,achieving automatic wear compensation.Based on fluid-solid coupling technology,the structural strength of the rotary sealing device was checked.The influence of factors on the sealing performance of rotary sealing devices was studied using the control variable method.The results show that as the pressure of water increases,the leakage rate of the sealing device decreases,and after 30 MPa,the leakage rate is almost 0 mL/h.The temperature of the rotating sealing device increases with the increase of rotation speed or pressure,and the temperature is more affected by the rotation speed factor.The frictional torque increases with increasing pressure and is independent of rotational speed.Comprehensive analysis shows that the wear resistance and reliability level of the sealing guide sleeve material is PVDF>PEEK>PE>PA.This study designs a high-pressure automatic compensation wear rotary sealing device and selects the optimal sealing material,providing technical support for the application of high-pressure water jet in mining machinery.
基金supported by the National Natural Science Foundation of China(No.52005470)the Natural Science Foundation of Zhejiang Province(No.LQ21E050020)the Fundamental Research Funds for the Provincial Universities of Zhejiang(No.2021YW17),China.
文摘The nitrile butadiene rubber(NBR)hardness effect on the sealing characteristics of hydraulic O-ring rod seals is analyzed based on a mixed lubrication elastohydrodynamic model.Parameterized studies are conducted to reveal the mechanism of the influence of rubber hardness on the static and dynamic behavior of seals.The optimized selections of rubber hardness are then investigated under different conditions.Results show that the low hardness seal is prone to stress concentration due to the extrusion effect under high pressure conditions;it is also more prone to leaking.A high hardness seal can better prevent leakage by reducing film thickness but it will cause large frictional power loss and increase the probability of wear failure.The choice of low hardness is recommended to reduce friction with the premise that leakage requirements are met.
文摘The static sealing of underground gas storage(UGS),including the integrity of cap rocks and the stability of faults,is analyzed from a macro perspective using a comprehensive geological evaluation method.Changes in pore structure,permeability,and mechanical strength of cap rocks under cyclic loads may impact the rock sealing integrity during the injection and recovery phases of UGS.In this work,the mechanical deformation and failure tests of rocks,as well as rock damage tests under alternating loads,are conducted to analyze the changes in the strength and permeability of rocks under multiple-cycle intense injection and recovery of UGS.Additionally,this study proposes an evaluation method for the dynamic sealing performance of UGS cap rocks under multi-cycle alternating loads.The findings suggest that the failure strength(70%)can be used as the critical value for rock failure,thus providing theoretical support for determining the upper limit of operating pressure and the number of injection-recovery cycles for the safe operation of a UGS system.
文摘Evaluating underground gas storage(UGS)sealing capacity is essential for its safe construction and operational efficiency.This involves evaluating both the static sealing capacity of traps during hydrocarbon accumulation and the dynamic sealing capacity of UGS under intensive gas injection and withdrawal,and alternating loads.This study detailed the methodology developed by Sinopec.The approach merges disciplines like geology,geomechanics,and hydrodynamics,employing both dynamic-static and qualitative-quantitative analyses.Sinopec's evaluation methods,grounded in the in situ stress analysis,include mechanistic studies,laboratory tests,geological surveys,stress analysis,and fluid-solid interactions.Through tests on the static and dynamic sealing capacity of UGS,alongside investigations into sealing mechanisms and the geological and geomechanical properties of cap rocks and faults,A geomechanics-rock damage-seepage mechanics dynamic coupling analysis method has been developed to predict in situ stress variations relative to pore pressure changes during UGS operations and evaluate fault sealing capacity and cap rock integrity,thereby setting the maximum operational pressures.Utilizing this evaluation technique,Sinopec has defined performance metrics and criteria for evaluating the sealing capacity of depleted gas reservoirs,enabling preliminary sealing capacity evaluations at UGS sites.These evaluations have significantly informed the design of UGS construction schemes and the evaluation of fault sealing capacity and cap rock integrity during UGS operations.
基金funded by the National Natural Science Foundation of China(Grant No.42172147)PetroChina Major Science and Technology Project(Grant No.ZD2019-183-002).
文摘Gypsum caprocks'sealing ability is affected by temperature-pressure coupling.Due to the limitations of experimental conditions,there is still a lack of triaxial stress-strain experiments that simultaneously consider changes in temperature and pressure conditions,which limits the accuracy of the comprehensive evaluation of the brittle plastic evolution and sealing ability of gypsum rocks using temperature pressure coupling.Triaxial stress-strain tests were utilized to investigate the differences in the evolution of the confinement capacity of gypsum rocks under coupled temperaturepressure action and isothermal-variable pressure action on the basis of sample feasibility analysis.According to research,the gypsum rock's peak and residual strengths decrease under simultaneous increases in temperature and pressure over isothermal pressurization experimental conditions,and it becomes more ductile.This reduces the amount of time it takes for the rock to transition from brittle to plastic.When temperature is taken into account,both the brittle–plastic transformation's depth limit and the lithological transformation of gypsum rocks become shallower,and the evolution of gypsum rocks under variable temperature and pressure conditions is more complicated than that under isothermal pressurization.The sealing ability under the temperature-pressure coupling is more in line with the actual geological context when the application results of the Well#ZS5 are compared.This provides a theoretical basis for precisely determining the process of hydrocarbon accumulation and explains why the early hydrocarbon were not well preserved.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(Grant No.52274009)China Postdoctoral Science Foundation(Grant No.2022M723501)Science and Technology Planning Project of Sichuan Province(Grant No.2021YJ0359).
文摘Lost circulation is a common downhole problem of drilling in geothermal and high-temperature,high-pressure(HTHP)formations.Lost circulation material(LCM)is a regular preventive and remedial measure for lost circulation.However,conventional LCMs seem ineffective in high-temperature formations.This may be due to the changes in the mechanical properties of LCMs and their sealing performance under high-temperature conditions.To understand how high temperature affects the fracture sealing performance of LCMs,we developed a coupled computational fluid dynamics-discrete element method(CFD-DEM)model to simulate the behavior of granular LCMs in fractures.We summarized the literature on the effects of high temperature on the mechanical properties of LCMs and the rheological properties of drilling fluid.We conducted sensitivity analyses to investigate how changing LCM slurry properties affected the fracture sealing efficiency at increasing temperatures.The results show that high temperature reduces the size,strength,and friction coefficient of LCMs as well as the drilling fluid viscosity.Smaller,softer,and less frictional LCM particles have lower bridging probability and slower bridging initiation.Smaller particles tend to form dual-particle bridges rather than single-particle bridges.These result in a deeper,tighter,but unstable sealing zone.Reduced drilling fluid viscosity leads to faster and shallower sealing zones.
