This study primarily investigates the rock fracture mechanism of bottom cushion layer blasting and explores the effects of the bottom cushion layer on rock fragmentation.It involves analyses of the evolution patterns ...This study primarily investigates the rock fracture mechanism of bottom cushion layer blasting and explores the effects of the bottom cushion layer on rock fragmentation.It involves analyses of the evolution patterns of blasting stress,characteristics of crack distribution,and rock fracture features in the specimens.First,blasting model experiments were carried out using the dynamic caustics principle to investigate the influence of bottom cushion layers and initiation methods on the integrity of the bottom rock mass.The experimental results indicate that the combined use of bottom cushion layers and inverse initiation effectively protects the integrity of the bottom rock mass.Subsequently,the process of stress wave propagation and dynamic crack propagation in rocks was simulated using the continuum-discontinuum element method(CDEM)and the Landau explosion source model,with varying thicknesses of bottom cushion layers.The numerical simulation results indicate that with increasing cushion thickness,the absorption of energy generated by the explosion becomes more pronounced,resulting in fewer cracks in the bottom rock mass.This illustrates the positive role of the cushion layer in protecting the integrity of the bottom rock mass.展开更多
This study investigated the development of mycelium-based biofoams as sustainable cushioning materials using Pleurotus ostreatus and Lentinus squarrosulus,combined with different sawdust substrates,and subjected to va...This study investigated the development of mycelium-based biofoams as sustainable cushioning materials using Pleurotus ostreatus and Lentinus squarrosulus,combined with different sawdust substrates,and subjected to various pressing methods.The results indicated significant effects of mushroom species,sawdust type,and pressing method on the properties of biofoams.Growth rate,morphology,chemical composition,physical and mechanical properties,water resistance,and cushioning factor were evaluated.The results indicated that Lentinus squarrosulus(LS)exhibited faster growth rates(up to 14.37 mm/day)and produced biofoams with superior properties compared to Pleurotus ostreatus(PO).Core wood(CW)sawdust generally resulted in biofoams with lower density(0.1-0.3 g/cm^(3)),lower shrinkage(7.17%-11.41%),and better shock absorption properties(cushion factor of 4.45-4.73).Hot pressing(HO)consistently produced biofoams with higher density(up to 0.31 g/cm^(3)),improved mechanical strength(compression strength up to 0.53 MPa),and enhanced hydrophobicity(water contact angle up to 102.03°)but slightly reduced the shock absorption performance.Biofoam made from LS cultivated on CW sawdust and pressed using hand-packing(HP)exhibited superior shock absorption properties,achieving a cushion factor of 4.45 comparable to expanded polystyrene(EPS)foam.The findings demonstrated that certain combinations of sawdust types and pressing methods can optimize the performance of mycelium-based biofoams,making them viable for sustainable packaging applications.This study highlighted the potential of mycelium biofoams as an eco-friendly alternative to conventional packaging materials,thereby decreasing environmental impact and promoting a sustainable future.展开更多
Rock sheds are widely used to prevent rockfall disasters along roads in mountainous areas.To improve the capacity of rock sheds for resisting rockfall impact,a sand and expandable polyethylene(EPE)composite cushion wa...Rock sheds are widely used to prevent rockfall disasters along roads in mountainous areas.To improve the capacity of rock sheds for resisting rockfall impact,a sand and expandable polyethylene(EPE)composite cushion was proposed.A series of model experiments of rockfall impact on rock sheds were conducted,and the buried depth of the EPE foam board in the sand layer was considered.The impact load and dynamic response of the rock shed were investigated.The results show that the maximum impact load and dynamic response of the rock shed roof are all significantly less than those of the sand cushion.Moreover,as the distance between the EPE foam board and rock shed roof decreases,the maximum rockfall impact force and impact pressure gradually decrease,and the maximum displacement,acceleration and strain of the rock shed first decrease and then change little.In addition,the vibration acceleration and vertical displacement of the rock shed roof decrease from the centre to the edge and decrease faster along the longitudinal direction than that along the transverse direction.In conclusion,the buffering effect of the sand-EPE composite cushion is better than that of the pure sand cushion,and the EPE foam board at a depth of 1/3 the thickness of the sand layer is appropriate.展开更多
Rock shed is an effective protection measure against rockfall.To investigate the influences of falling rock’s shape and impact angle on the impact effect of the cushioned rock shed,a modeling approach for a rock shed...Rock shed is an effective protection measure against rockfall.To investigate the influences of falling rock’s shape and impact angle on the impact effect of the cushioned rock shed,a modeling approach for a rock shed with a cushion layer using PFC-FLAC.The granular cushion is modeled as an aggregate of discrete non-cohesion particles,while the concrete plate and the beam are modeled as zones.The falling rock with different sphericities and impact angles is modeled as a rigid assembly.The numerical model is validated by comparing the simulation results with experimental and numerical results from previous literature.This model is applied to analyze the effects of rock shape and impact angle on the dynamic interaction effects between falling rock and cushioned rock shed,including the impact force,transmitted bottom force,penetration depth,and plate deflection.The numerical results show that the variation in the falling rock’s shape has different effects on the falling rock with different impact angles.These findings could support rock shed design by revealing the limitations of the assumptions in the past research,which may result in unsafe rock sheds for some rockfall cases.展开更多
Through a self-developed model test system,the mechanical properties of silt and the deformation characteristics of airport runways were investigated during the period of subgrade wetting.Based on the test results,the...Through a self-developed model test system,the mechanical properties of silt and the deformation characteristics of airport runways were investigated during the period of subgrade wetting.Based on the test results,the reliability of the numerical simulation results was verified.Numerical models with different sizes were established.Under the same cushion parameter and loading width ranges,the effects of the cushion parameters and loading conditions on the mechanical responses of the cushion before and after subgrade wetting were analyzed.The results show that the internal friction angles of silt with different wetting degrees are approximately 34°.The cohesion is from 8 to 44 kPa,and the elastic modulus is from 15 to 34 MPa.Before and after subgrade wetting,the variation rates of the cushion horizontal tensile stresses with the same cushion parameters and loading width ranges are different under the influence of boundary effects.After subgrade wetting,the difference in the variation rates of the cushion horizontal tensile stresses under the same cushion parameter range decreases compared with that before subgrade wetting;however,this difference increases under the same loading width range.Before and after subgrade wetting,the influence of the boundary effect on the mechanical response evaluation of the cushion is not beneficial for optimizing the pavement design parameters.When the cushion thickness is more than 0.25 m,the influence of the boundary effect can be disregarded.展开更多
The analysis of the characteristics of the cushion process of the pneumatic cushion cylinder is presented, and the nonlinear model of pneumatic cushion cylinders is built in the form of nonlinear differential equation...The analysis of the characteristics of the cushion process of the pneumatic cushion cylinder is presented, and the nonlinear model of pneumatic cushion cylinders is built in the form of nonlinear differential equations. Besides, through the simulation of the pressure in the cushion chamber, the characteristics of the pneumatic cushion cylinder are obtained, which helps to understand the performance of the pneumatic cushion cylinder and improve or design the better cushion structure.展开更多
Bridge foundations located in deep water are usually subjected to horizontal dynamic loads and moments which may be caused by the wind, waves, earthquake, and the possibility of boat crashing or vehicle braking. Caiss...Bridge foundations located in deep water are usually subjected to horizontal dynamic loads and moments which may be caused by the wind, waves, earthquake, and the possibility of boat crashing or vehicle braking. Caisson foundations based on gravel or sand cushions are a new type of deep-water foundation for bridges, suitable for meizoseismal areas. In this paper, harmonic horizontal excitation tests for the study of the lateral dynamic response of caisson foundations based on cushion layers are described. Different lateral loads and two different cushion types are considered. The results show that the lateral dynamic responses of caisson foundations based on sand and gravel cushions both show strong nonlinear characteristics, and the resonant frequency of the foundation decreases with the increase of the excitation force. The dynamic displacement of a foundation based on a sand cushion is far less than that based on a gravel cushion, and the rate of decrease of the resonant frequency of a foundation based on a gravel cushion is faster than that of a foundation based on a sand cushion under the same conditions. Under dynamic loading the gravel cushion can more effectively dissipate vibration energy and isolate the vibration, than the sand cushion can. A simplified nonlinear analysis method is proposed to simulate the lateral dynamic response of caisson foundations, and the predicted response shows a reasonable match with the results observed in laboratory tests. Scaling laws have also been applied in this small-scale vibration model test to predict the dynamic behavior of the prototype foundation.展开更多
It is very important to develop new air-cushion nozzles so as to raise the heat treatment property of aluminum alloy automobile body sheet(ABS). A geometric model of air-cushion furnace equipment of ABS was built up a...It is very important to develop new air-cushion nozzles so as to raise the heat treatment property of aluminum alloy automobile body sheet(ABS). A geometric model of air-cushion furnace equipment of ABS was built up and flow field was simulated by using k-ε turbulence equations of COMSOL Multi-physics. The influence and regularity of number(n),diameter(d) and arrangement of middle hole,and main control parameters of new air-cushion nozzle on aerodynamic characteristics and flow field were studied. The results show that:1) with n increases,airflow vortexes in air-cushion area increase in multiple; d decreases or n increases,air cushion pressure(p_c) becomes uniform; 2) average of p_c is proportional to pressure in nozzle box(p_t),when n increases,ratio of average of p_c to p_t increases,and when n ≤ 3 and d < b / 2,they have little effect on ratio of p_c average to p_t; 3) when n is an even number,n ≥4,and d ≤ b/2,p_c shows good uniformity; when n is an odd number,the center hole affects p_c uniformity greatly,and,when diameter of center hole is less than b / 4 and diameter of non-center is between b / 4 and b / 2,p_c has good uniformity. A new air-cushion jet model was presented,and the deviation of this new model with simulation data and experimental measured data are less than 7.75% and 7.76%,respectively. The present research is valuable for improving air-cushion stability,Al strip temperature homogeneity,and temperature control precision.展开更多
The isolated and anatomically_preserved lepidodendralean leaf cushions were described from coal balls in Wangjiazhai Formation (upper Upper Permian) in western Guizhou Province. These leaf cushions are very similar t...The isolated and anatomically_preserved lepidodendralean leaf cushions were described from coal balls in Wangjiazhai Formation (upper Upper Permian) in western Guizhou Province. These leaf cushions are very similar to Lepidodendron lepidophloides Yao both in size and morphology. They probably belong to the same species in different preservative condition. Comparisons on morphology and anatomy of L. lepidophloides and lepidodendralean leaf cushion genera, such as Lepidodendron, Lepidophloios, Sigillaria and Cathaysiodendron revealed that L. lepidophloides possesses mixed features of all these genera and it can not be assigned into any of them without doubt. It probably represents a new genus. Because the anatomical features of the other parts of the stem as well as the fertile organs related to these leaf cushions are unknown, the specific name L. lepidophloides is adopted. We leave this taxonomic problem open till the relationship between these leaf cushions and the stem and fertile organs become clear. This is the first report on the detailed anatomical features of the Cathaysian lepidodendralean leaf cushions.展开更多
An inside-cushion structure with sidestep and taper-shaped plungers is studied to address the problems of high impact and vibration in high-speed hydraulic cylinders.First,the three stages of cushion processes are dis...An inside-cushion structure with sidestep and taper-shaped plungers is studied to address the problems of high impact and vibration in high-speed hydraulic cylinders.First,the three stages of cushion processes are discussed according to the varying flow area as the piston moves.Then,to establish a precise mathematical model,the states of the flow field are estimated in terms of the Reynolds number.Accordingly,the simulation model parameterized against measured data is developed and verified by experiment.Last,the average velocity,peak cushion pressure,and terminal velocity are defined to evaluate cushion performance.According to these optimized objectives,the non-linear programming by quadratic Lagrange(NLPQL)algorithm is applied to optimize the structure parameters.The optimization results indicate that the peak cushion pressure is reduced by 28%and terminal velocity is reduced by 21%without reduction of average velocity.展开更多
AIM:To identify a more effective treatment protocol for circumferential mixed hemorrhoids.METHODS:A total of 192 patients with circumferential mixed hemorrhoids were randomized into the treatment group,where they unde...AIM:To identify a more effective treatment protocol for circumferential mixed hemorrhoids.METHODS:A total of 192 patients with circumferential mixed hemorrhoids were randomized into the treatment group,where they underwent Milligan-Morgan hemorrhoidectomy with anal cushion suspension and partial internal sphincter resection,or the control group,where traditional external dissection and internal ligation were performed.Postoperative recovery and complications were monitored.RESULTS:The time to wound healing was 12.96 ± 2.25 d in the treatment group shorter than 19.58 ± 2.71 d in the control group.Slight pain rate was 58.3% in the treatment group higher than 22.9% in the control group;moderate pain rate was 33.3% in the treatment group lower than 56.3% in the control group severe pain rate was 8.4% in the treatment group lower than 20.8% in the control group.No edema rate was 70.8% in the treatment group higher than 43.8% in the control group;mild local edema rate was 26% in the treatment group lower than 39.6% in the control group obvious local edema was 3.03% in the treatment group lower than 16.7% in the control group.No stenosis rate was 85.4% in the treatment group higher than 63.5% in the control group;moderate stenosis rate was 14.6% in the treatment group Lower than 27.1% in the control group severe anal stenosis rate was 0% in the treatment group lower than 9.4% in the control group.CONCLUSION:Milligan-Morgan hemorrhoidectomy with anal cushion suspension and partial internal sphincter resection is the optimal treatment for circumferential mixed hemorrhoids and can be widely applied in clinical settings.展开更多
During the second period of China ＂Tanyue＂ Project, the explorer will softland on the moon. The cushion engines are used to decelerate the explorer and reduce the impact on the lunar ground. It is necessary to study...During the second period of China ＂Tanyue＂ Project, the explorer will softland on the moon. The cushion engines are used to decelerate the explorer and reduce the impact on the lunar ground. It is necessary to study its plume effects on the explorer component. The self-developed PWS （Plume WorkStation） software based on direct simulation Monte Carlo （DSMC） method is used to simulate the plume effects of two 150 N engines. Due to the complex structure of the explorer, PWS uses a decoupling method to treat the boundary mesh, which mainly interacts with simulation particles, and has no relation with the computational grids. After the analytical expressions of plane surfaces and curved surfaces of each boundary block are given, the particle position within or without the boundary blocks can be easily determined. Finally the 3D plume field of two 150 N engines is simulated. The pressure, temperature and velocity distributions of plume field are clearly presented by three characteristic slices. The aerodynamic effects on the explorer bottom, the landfall legs and antenna are separately shown. The compression influence on the plume flow of four landfall legs can be observed.展开更多
AIM to evaluate the diagnostic value of different sonographic methods in hemorrhoids. METHODS Forty-two healthy volunteers and sixty-two patients with grades I -IV. hemorrhoids received two different sonographic exami...AIM to evaluate the diagnostic value of different sonographic methods in hemorrhoids. METHODS Forty-two healthy volunteers and sixty-two patients with grades I -IV. hemorrhoids received two different sonographic examinations from January 2013 to January 2016 at the First and Second Hospitals of Xinjiang Medical University in a prospective way. We analyzed the ultrasonographic findings of these participants and evaluated the outcomes. Resected grades. and. hemorrhoid tissues were pathologically examined. The concordance of ultrasonographic results with pathology results was assessed with the Cohen's kappa coefficient. RESULTS All healthy volunteers and all patients had no particular complications related to sonography. There were no statistically significant differences between the participants regarding age (P = 0.5919), gender (P = 0.4183), and persistent symptoms (P > 0.8692). All healthy control participants had no special findings. However, 30 patients with hemorrhoids showed blood signals around the dentate line on ultrasonography. When grades I and II hemorrhoids were analyzed, there were no significant differences between transrectal ultrasound (TRUS), transperianal ultrasound (TPUS), and transvaginal ultrasound (TVUS) (P > 0.05). Grades III and IV hemorrhoids revealed blood flow with different directions which could be observed as a 'mosaic pattern'. In patients with grades III and IV hemorrhoids, the number of patients with 'mosaic pattern' as revealed by TRUS, TPUS and TVUS was 22, 12, and 4, respectively. Patients with grades III and IV disease presented with a pathologically abnormal cushion which usually appeared as a 'mosaic pattern' in TPUS and an arteriovenous fistula in pathology. Subepithelial vessels of resected grades III and IV hemorrhoid tissues were manifested by obvious structural impairment and retrograde and ruptured changes of internal elastic lamina. Some parts of the Trietz's muscle showed hypertrophy and distortion. Arteriovenous fistulas and venous dilatation were obvious in the anal cushion of hemorhoidal tissues. After pathological results with arteriovenous fistulas were taken as the standard reference, we evaluated the compatibility between the two methods according to the Cohen's kappa co-efficiency calculation. The compatibility (Cohein kappa co-efficiency value) between 'mosaic pattern' in the TPUS and arteriovenous fistula in pathology was very good (K = 0.8939). When compared between different groups, TRUS presented the advantage that the mosaic pattern could be confirmed in more patients, especially for group A. There was a statistical difference when comparing group A with group B or C (P < 0.05 for both). There were obvious statistical differences between group A and group B with regard to the vessel diameter and blood flow velocity measured by TRUS (P < 0.05). CONCLUSION Patients with grades III and IV hemorrhoids present with a pathologically abnormal cushion which usually appears as a 'mosaic pattern' in sonography, which is in accord with an arteriovenous fistula in pathology. There are clearly different hemorrhoid structures shown by sonography. 'Mosaic pattern' may be a parameter for surgical indication of grades III and IV hemorrhoids.展开更多
To achieve durability of the embankment in southern China,a method to control the change of moisture content with the cushion and cover was proposed.A finite element model of cushion and cover considering different ma...To achieve durability of the embankment in southern China,a method to control the change of moisture content with the cushion and cover was proposed.A finite element model of cushion and cover considering different materials and thicknesses for a typical embankment was built,and 20 numerical analyses of transient seepage in the embankment were simulated.The results show that the sand cushion effectively blocks the effect of groundwater capillary rise and the minimum thickness of the sand cushion is 75 cm without considering the atmospheric environment.With the combination of sand cushion and clay cover,as the thickness of the clay cover increases,the duration time of the moisture content from the initial to relative equilibrium state increases,but the equilibrium moisture content is the same as that of the original embankment.Besides,with the combination of the sand cushion and sand cover,the moisture content inside the embankment remains the same,which is consistent with the optimum moisture content during construction.The combination of 75 cm sand cushion and 30 cm sand cover is a very effective method to block groundwater and atmospheric environment,and achieve the control of the humidity stability of the embankment in southern China.展开更多
This study proposes a new nonlinear tracking control method with safe angular velocity constraints for a cushion robot. A fuzzy path planning algorithm is investigated and a realtime desired motion path of obstacle av...This study proposes a new nonlinear tracking control method with safe angular velocity constraints for a cushion robot. A fuzzy path planning algorithm is investigated and a realtime desired motion path of obstacle avoidance is obtained. The angular velocity is constrained by the controller, so the planned path guarantees the safety of users. According to Lyapunov theory, the controller is designed to maintain stability in terms of solutions of linear matrix inequalities and the controller's performance with safe angular velocity constraints is derived.The simulation and experiment results confirm the effectiveness of the proposed method and verify that the angular velocity of the cushion robot provided safe motion with obstacle avoidance.展开更多
Cushion species occur in nearly all alpine environments worldwide. In past decades, the adaptive and ecosystem-engineering roles of such highly specialized life forms have been well studied. However, the adaptive stra...Cushion species occur in nearly all alpine environments worldwide. In past decades, the adaptive and ecosystem-engineering roles of such highly specialized life forms have been well studied. However, the adaptive strategies responsible for cushion species reproductive success and maintenance in severe alpine habitats remain largely unclear. In this study, we reviewed the current understanding of reproductive strategies and population persistence in alpine cushion species. We then present a preliminary case study on the sexual reproduction of Arenaria polytrichoides(Caryophyllaceae), a typical cushion species inhabiting high elevations of the Himalaya Hengduan Mountains, which is a hotspot for diversification of cushion species. Finally, we highlight the limitations of our current understanding of alpine cushion species reproduction and propose future directions for study.展开更多
This paper uses the discrete element method to model the size and cushion effects during single-particle crushing tests.We propose simplified numerical modeling to examine the effects of particle size and coordination...This paper uses the discrete element method to model the size and cushion effects during single-particle crushing tests.We propose simplified numerical modeling to examine the effects of particle size and coordination number on particle breakage behavior.We validate the proposed modeling by comparing the numerical results with the experimental data reported in the literature,in terms of the variability of particle tensile strength and axial force-displacement responses.Based on the numerical results,it is clear that a larger particle size entails a higher tensile strength with a larger discreteness.In addition,the characteristic tensile strength increases linearly with an increasing coordination number.Moreover,smaller particles are more susceptible to the cushion effect than larger particles.The numerical results also indicate that an increasing coordination number induces a more ductile mode of failure.Based on these results,we propose an empirical equation for calculating tensile strength,incorporating both the cushion effect and the size effect.展开更多
Positive associations between alpine cushion plants and other species have been extensively studied.However,almost all studies have focused on the associations between macrofauna.Studies that have investigated positiv...Positive associations between alpine cushion plants and other species have been extensively studied.However,almost all studies have focused on the associations between macrofauna.Studies that have investigated positive associations between alpine cushion plants and rhizospheric microbes have been limited to the vegetation growing season.Here,we asked whether the positive effects that alpine cushion plants confer on rhizospheric microbe communities vary with seasons.We assessed seasonal variations in the bacterial diversity and composition in rhizosphere of two alpine cushion plants and surrounding bare ground by employing a high throughput sequencing method targeting the V3 region of bacterial 16 S rRNA genes.Soil properties of the rhizosphere and the bare ground were also examined.We found that cushion rhizospheres harbored significantly more C,N,S,ammonia nitrogen,and soil moisture than the bare ground.Soil properties in cushion rhizospheres were not notably different,except for soil pH.Bacterial diversities within the same microhabitats did not vary significantly with seasons.We concluded that alpine cushion plants had positive effects on the rhizospheric bacterial communities,even though the strength of the effect varied in different cushion species.Cushion species and the soil sulfur content were probably the major factors driving the spatial distribution and structure of soil bacterial communities in the alpine communities dominated by cushion plants.展开更多
AIM: To describe the anal cushion lifting(ACL) method with preliminary clinical results. METHODS: Between January to September 2007, 127 patients who received ACL method for hemorrhoid was investigated with informed c...AIM: To describe the anal cushion lifting(ACL) method with preliminary clinical results. METHODS: Between January to September 2007, 127 patients who received ACL method for hemorrhoid was investigated with informed consent. In this study, three surgeons who specialized in anorectal surgery performed the procedures. Patients with grade two or more severe hemorrhoids according to Goligher's classification were considered to be indicated for surgery. The patients were given the choice to undergo either the ACL method or theligation and excision method. ACL method is an original technique for managing hemorrhoids without excision. After dissecting the anal cushion from the internal sphincter muscle, the anal cushion was lifted to oral side and ligated at the proper position. Clinical characteristics and outcomes of patients were recorded including complications after surgery. RESULTS: A total of 127 patients were enrolled. Their median age was 42(19-84) years, and 74.8% were female. In addition, more than 99% of the patients had grade 3 or worse hemorrhoids. The median followup period was 26(0-88) mo, and the median operative time was 15(4-30) min. After surgery, analgesics were used for a median period of three days(0-21). Pain control was achieved using extra-oral analgesic drugs, although some patients required intravenous injections of analgesic drugs. The median duration of the patients' postoperative hospital stay was 7(2-13) d. A total of 10 complications(7.9%) occurred. Bleeding was observed in one patient and was successfully controlled with manual compression. Urinary retention occurred in 6 patients, but it disappeared spontaneously in all cases. Recurrent hemorrhoids developed in 3 patients after 36, 47, and 61 mo, respectively. No anal stenosis or persistent anal pain occurred. CONCLUSION: We consider that the ACL method might be better than all other current methods for managing hemorrhoids.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52204085 and 52104074)the Youth Science and Technology Foundation Key Laboratory for Mechanics in Fluid Solid Coupling System,Institute of Mechanics(No.E0XM040401)。
文摘This study primarily investigates the rock fracture mechanism of bottom cushion layer blasting and explores the effects of the bottom cushion layer on rock fragmentation.It involves analyses of the evolution patterns of blasting stress,characteristics of crack distribution,and rock fracture features in the specimens.First,blasting model experiments were carried out using the dynamic caustics principle to investigate the influence of bottom cushion layers and initiation methods on the integrity of the bottom rock mass.The experimental results indicate that the combined use of bottom cushion layers and inverse initiation effectively protects the integrity of the bottom rock mass.Subsequently,the process of stress wave propagation and dynamic crack propagation in rocks was simulated using the continuum-discontinuum element method(CDEM)and the Landau explosion source model,with varying thicknesses of bottom cushion layers.The numerical simulation results indicate that with increasing cushion thickness,the absorption of energy generated by the explosion becomes more pronounced,resulting in fewer cracks in the bottom rock mass.This illustrates the positive role of the cushion layer in protecting the integrity of the bottom rock mass.
基金supported by the Graduate School,Prince of Songkla University。
文摘This study investigated the development of mycelium-based biofoams as sustainable cushioning materials using Pleurotus ostreatus and Lentinus squarrosulus,combined with different sawdust substrates,and subjected to various pressing methods.The results indicated significant effects of mushroom species,sawdust type,and pressing method on the properties of biofoams.Growth rate,morphology,chemical composition,physical and mechanical properties,water resistance,and cushioning factor were evaluated.The results indicated that Lentinus squarrosulus(LS)exhibited faster growth rates(up to 14.37 mm/day)and produced biofoams with superior properties compared to Pleurotus ostreatus(PO).Core wood(CW)sawdust generally resulted in biofoams with lower density(0.1-0.3 g/cm^(3)),lower shrinkage(7.17%-11.41%),and better shock absorption properties(cushion factor of 4.45-4.73).Hot pressing(HO)consistently produced biofoams with higher density(up to 0.31 g/cm^(3)),improved mechanical strength(compression strength up to 0.53 MPa),and enhanced hydrophobicity(water contact angle up to 102.03°)but slightly reduced the shock absorption performance.Biofoam made from LS cultivated on CW sawdust and pressed using hand-packing(HP)exhibited superior shock absorption properties,achieving a cushion factor of 4.45 comparable to expanded polystyrene(EPS)foam.The findings demonstrated that certain combinations of sawdust types and pressing methods can optimize the performance of mycelium-based biofoams,making them viable for sustainable packaging applications.This study highlighted the potential of mycelium biofoams as an eco-friendly alternative to conventional packaging materials,thereby decreasing environmental impact and promoting a sustainable future.
基金supported by the Natural Science Foundation of Sichuan Province(No.2022NSFSC1127)the Fundamental Research Funds for the Central Universities(No.2682023CX075).
文摘Rock sheds are widely used to prevent rockfall disasters along roads in mountainous areas.To improve the capacity of rock sheds for resisting rockfall impact,a sand and expandable polyethylene(EPE)composite cushion was proposed.A series of model experiments of rockfall impact on rock sheds were conducted,and the buried depth of the EPE foam board in the sand layer was considered.The impact load and dynamic response of the rock shed were investigated.The results show that the maximum impact load and dynamic response of the rock shed roof are all significantly less than those of the sand cushion.Moreover,as the distance between the EPE foam board and rock shed roof decreases,the maximum rockfall impact force and impact pressure gradually decrease,and the maximum displacement,acceleration and strain of the rock shed first decrease and then change little.In addition,the vibration acceleration and vertical displacement of the rock shed roof decrease from the centre to the edge and decrease faster along the longitudinal direction than that along the transverse direction.In conclusion,the buffering effect of the sand-EPE composite cushion is better than that of the pure sand cushion,and the EPE foam board at a depth of 1/3 the thickness of the sand layer is appropriate.
基金supported by the National Natural Science Foundation of China(Grant Nos.41941017 and U1702241).
文摘Rock shed is an effective protection measure against rockfall.To investigate the influences of falling rock’s shape and impact angle on the impact effect of the cushioned rock shed,a modeling approach for a rock shed with a cushion layer using PFC-FLAC.The granular cushion is modeled as an aggregate of discrete non-cohesion particles,while the concrete plate and the beam are modeled as zones.The falling rock with different sphericities and impact angles is modeled as a rigid assembly.The numerical model is validated by comparing the simulation results with experimental and numerical results from previous literature.This model is applied to analyze the effects of rock shape and impact angle on the dynamic interaction effects between falling rock and cushioned rock shed,including the impact force,transmitted bottom force,penetration depth,and plate deflection.The numerical results show that the variation in the falling rock’s shape has different effects on the falling rock with different impact angles.These findings could support rock shed design by revealing the limitations of the assumptions in the past research,which may result in unsafe rock sheds for some rockfall cases.
基金The National Natural Science Foundation of China(No.52008401)the Natural Science Foundation of Hunan Province(No.2021JJ40770)the Open Fund of Hunan Tieyuan Civil Engineering Testing Co.,Ltd.(No.HNTY2022K04).
文摘Through a self-developed model test system,the mechanical properties of silt and the deformation characteristics of airport runways were investigated during the period of subgrade wetting.Based on the test results,the reliability of the numerical simulation results was verified.Numerical models with different sizes were established.Under the same cushion parameter and loading width ranges,the effects of the cushion parameters and loading conditions on the mechanical responses of the cushion before and after subgrade wetting were analyzed.The results show that the internal friction angles of silt with different wetting degrees are approximately 34°.The cohesion is from 8 to 44 kPa,and the elastic modulus is from 15 to 34 MPa.Before and after subgrade wetting,the variation rates of the cushion horizontal tensile stresses with the same cushion parameters and loading width ranges are different under the influence of boundary effects.After subgrade wetting,the difference in the variation rates of the cushion horizontal tensile stresses under the same cushion parameter range decreases compared with that before subgrade wetting;however,this difference increases under the same loading width range.Before and after subgrade wetting,the influence of the boundary effect on the mechanical response evaluation of the cushion is not beneficial for optimizing the pavement design parameters.When the cushion thickness is more than 0.25 m,the influence of the boundary effect can be disregarded.
文摘The analysis of the characteristics of the cushion process of the pneumatic cushion cylinder is presented, and the nonlinear model of pneumatic cushion cylinders is built in the form of nonlinear differential equations. Besides, through the simulation of the pressure in the cushion chamber, the characteristics of the pneumatic cushion cylinder are obtained, which helps to understand the performance of the pneumatic cushion cylinder and improve or design the better cushion structure.
基金supported by the National Natural Science Foundation of China(Nos.51808220 and 51822809)the Natural Science Foundation of Jiangxi Province(Nos.20192BAB216036 and 20181BCB24011)the Science and Technology Research Project of the Education Department of Jiangxi Province(No.GJJ180340),China。
文摘Bridge foundations located in deep water are usually subjected to horizontal dynamic loads and moments which may be caused by the wind, waves, earthquake, and the possibility of boat crashing or vehicle braking. Caisson foundations based on gravel or sand cushions are a new type of deep-water foundation for bridges, suitable for meizoseismal areas. In this paper, harmonic horizontal excitation tests for the study of the lateral dynamic response of caisson foundations based on cushion layers are described. Different lateral loads and two different cushion types are considered. The results show that the lateral dynamic responses of caisson foundations based on sand and gravel cushions both show strong nonlinear characteristics, and the resonant frequency of the foundation decreases with the increase of the excitation force. The dynamic displacement of a foundation based on a sand cushion is far less than that based on a gravel cushion, and the rate of decrease of the resonant frequency of a foundation based on a gravel cushion is faster than that of a foundation based on a sand cushion under the same conditions. Under dynamic loading the gravel cushion can more effectively dissipate vibration energy and isolate the vibration, than the sand cushion can. A simplified nonlinear analysis method is proposed to simulate the lateral dynamic response of caisson foundations, and the predicted response shows a reasonable match with the results observed in laboratory tests. Scaling laws have also been applied in this small-scale vibration model test to predict the dynamic behavior of the prototype foundation.
基金Sponsored by Science and Technology Project of Liaoning Province(Grant No.L2013113)the Fundamental Research Funds for the Central Universities(Grant No.N140703002)
文摘It is very important to develop new air-cushion nozzles so as to raise the heat treatment property of aluminum alloy automobile body sheet(ABS). A geometric model of air-cushion furnace equipment of ABS was built up and flow field was simulated by using k-ε turbulence equations of COMSOL Multi-physics. The influence and regularity of number(n),diameter(d) and arrangement of middle hole,and main control parameters of new air-cushion nozzle on aerodynamic characteristics and flow field were studied. The results show that:1) with n increases,airflow vortexes in air-cushion area increase in multiple; d decreases or n increases,air cushion pressure(p_c) becomes uniform; 2) average of p_c is proportional to pressure in nozzle box(p_t),when n increases,ratio of average of p_c to p_t increases,and when n ≤ 3 and d < b / 2,they have little effect on ratio of p_c average to p_t; 3) when n is an even number,n ≥4,and d ≤ b/2,p_c shows good uniformity; when n is an odd number,the center hole affects p_c uniformity greatly,and,when diameter of center hole is less than b / 4 and diameter of non-center is between b / 4 and b / 2,p_c has good uniformity. A new air-cushion jet model was presented,and the deviation of this new model with simulation data and experimental measured data are less than 7.75% and 7.76%,respectively. The present research is valuable for improving air-cushion stability,Al strip temperature homogeneity,and temperature control precision.
文摘The isolated and anatomically_preserved lepidodendralean leaf cushions were described from coal balls in Wangjiazhai Formation (upper Upper Permian) in western Guizhou Province. These leaf cushions are very similar to Lepidodendron lepidophloides Yao both in size and morphology. They probably belong to the same species in different preservative condition. Comparisons on morphology and anatomy of L. lepidophloides and lepidodendralean leaf cushion genera, such as Lepidodendron, Lepidophloios, Sigillaria and Cathaysiodendron revealed that L. lepidophloides possesses mixed features of all these genera and it can not be assigned into any of them without doubt. It probably represents a new genus. Because the anatomical features of the other parts of the stem as well as the fertile organs related to these leaf cushions are unknown, the specific name L. lepidophloides is adopted. We leave this taxonomic problem open till the relationship between these leaf cushions and the stem and fertile organs become clear. This is the first report on the detailed anatomical features of the Cathaysian lepidodendralean leaf cushions.
基金National Natural Science Foundation of China(51705152)Jiangxi Provincial Natural Science Foundation(20161BAB206150+2 种基金20161BAB216133)Jiangxi Provincial Key R&D Program(20171BBG70040)Innovation Fund Designated for Graduate Students of Jiangxi Province(YC2018-S246)。
文摘An inside-cushion structure with sidestep and taper-shaped plungers is studied to address the problems of high impact and vibration in high-speed hydraulic cylinders.First,the three stages of cushion processes are discussed according to the varying flow area as the piston moves.Then,to establish a precise mathematical model,the states of the flow field are estimated in terms of the Reynolds number.Accordingly,the simulation model parameterized against measured data is developed and verified by experiment.Last,the average velocity,peak cushion pressure,and terminal velocity are defined to evaluate cushion performance.According to these optimized objectives,the non-linear programming by quadratic Lagrange(NLPQL)algorithm is applied to optimize the structure parameters.The optimization results indicate that the peak cushion pressure is reduced by 28%and terminal velocity is reduced by 21%without reduction of average velocity.
文摘AIM:To identify a more effective treatment protocol for circumferential mixed hemorrhoids.METHODS:A total of 192 patients with circumferential mixed hemorrhoids were randomized into the treatment group,where they underwent Milligan-Morgan hemorrhoidectomy with anal cushion suspension and partial internal sphincter resection,or the control group,where traditional external dissection and internal ligation were performed.Postoperative recovery and complications were monitored.RESULTS:The time to wound healing was 12.96 ± 2.25 d in the treatment group shorter than 19.58 ± 2.71 d in the control group.Slight pain rate was 58.3% in the treatment group higher than 22.9% in the control group;moderate pain rate was 33.3% in the treatment group lower than 56.3% in the control group severe pain rate was 8.4% in the treatment group lower than 20.8% in the control group.No edema rate was 70.8% in the treatment group higher than 43.8% in the control group;mild local edema rate was 26% in the treatment group lower than 39.6% in the control group obvious local edema was 3.03% in the treatment group lower than 16.7% in the control group.No stenosis rate was 85.4% in the treatment group higher than 63.5% in the control group;moderate stenosis rate was 14.6% in the treatment group Lower than 27.1% in the control group severe anal stenosis rate was 0% in the treatment group lower than 9.4% in the control group.CONCLUSION:Milligan-Morgan hemorrhoidectomy with anal cushion suspension and partial internal sphincter resection is the optimal treatment for circumferential mixed hemorrhoids and can be widely applied in clinical settings.
基金supported by the "Tanyue" Period Two Research Projects
文摘During the second period of China ＂Tanyue＂ Project, the explorer will softland on the moon. The cushion engines are used to decelerate the explorer and reduce the impact on the lunar ground. It is necessary to study its plume effects on the explorer component. The self-developed PWS （Plume WorkStation） software based on direct simulation Monte Carlo （DSMC） method is used to simulate the plume effects of two 150 N engines. Due to the complex structure of the explorer, PWS uses a decoupling method to treat the boundary mesh, which mainly interacts with simulation particles, and has no relation with the computational grids. After the analytical expressions of plane surfaces and curved surfaces of each boundary block are given, the particle position within or without the boundary blocks can be easily determined. Finally the 3D plume field of two 150 N engines is simulated. The pressure, temperature and velocity distributions of plume field are clearly presented by three characteristic slices. The aerodynamic effects on the explorer bottom, the landfall legs and antenna are separately shown. The compression influence on the plume flow of four landfall legs can be observed.
基金the National Natural Science Foundation of China,No.81460133Innovation Program of regional Cooperation of Xinjiang Uygur Autonomous region,No.2016E02063
文摘AIM to evaluate the diagnostic value of different sonographic methods in hemorrhoids. METHODS Forty-two healthy volunteers and sixty-two patients with grades I -IV. hemorrhoids received two different sonographic examinations from January 2013 to January 2016 at the First and Second Hospitals of Xinjiang Medical University in a prospective way. We analyzed the ultrasonographic findings of these participants and evaluated the outcomes. Resected grades. and. hemorrhoid tissues were pathologically examined. The concordance of ultrasonographic results with pathology results was assessed with the Cohen's kappa coefficient. RESULTS All healthy volunteers and all patients had no particular complications related to sonography. There were no statistically significant differences between the participants regarding age (P = 0.5919), gender (P = 0.4183), and persistent symptoms (P > 0.8692). All healthy control participants had no special findings. However, 30 patients with hemorrhoids showed blood signals around the dentate line on ultrasonography. When grades I and II hemorrhoids were analyzed, there were no significant differences between transrectal ultrasound (TRUS), transperianal ultrasound (TPUS), and transvaginal ultrasound (TVUS) (P > 0.05). Grades III and IV hemorrhoids revealed blood flow with different directions which could be observed as a 'mosaic pattern'. In patients with grades III and IV hemorrhoids, the number of patients with 'mosaic pattern' as revealed by TRUS, TPUS and TVUS was 22, 12, and 4, respectively. Patients with grades III and IV disease presented with a pathologically abnormal cushion which usually appeared as a 'mosaic pattern' in TPUS and an arteriovenous fistula in pathology. Subepithelial vessels of resected grades III and IV hemorrhoid tissues were manifested by obvious structural impairment and retrograde and ruptured changes of internal elastic lamina. Some parts of the Trietz's muscle showed hypertrophy and distortion. Arteriovenous fistulas and venous dilatation were obvious in the anal cushion of hemorhoidal tissues. After pathological results with arteriovenous fistulas were taken as the standard reference, we evaluated the compatibility between the two methods according to the Cohen's kappa co-efficiency calculation. The compatibility (Cohein kappa co-efficiency value) between 'mosaic pattern' in the TPUS and arteriovenous fistula in pathology was very good (K = 0.8939). When compared between different groups, TRUS presented the advantage that the mosaic pattern could be confirmed in more patients, especially for group A. There was a statistical difference when comparing group A with group B or C (P < 0.05 for both). There were obvious statistical differences between group A and group B with regard to the vessel diameter and blood flow velocity measured by TRUS (P < 0.05). CONCLUSION Patients with grades III and IV hemorrhoids present with a pathologically abnormal cushion which usually appears as a 'mosaic pattern' in sonography, which is in accord with an arteriovenous fistula in pathology. There are clearly different hemorrhoid structures shown by sonography. 'Mosaic pattern' may be a parameter for surgical indication of grades III and IV hemorrhoids.
基金Project(2017YFC0805307)supported by the National Key Research and Development Program of ChinaProjects(51838001,51878070,51878078,51911530215,51927814)supported by the National Natural Science Foundation of China+5 种基金Project(2018JJ1026)supported by the Excellent Youth Foundation of Natural Science Foundation of Hunan Province,ChinaProject(17A008)supported by the Key Project of Education Department of Hunan Province,ChinaProjects(kfj150103,kfj170106)supported by the Changsha University of Science&Technology via Key Project of Open Research Fund of National Engineering Laboratory of Highway Maintenance Technology,ChinaProject(kfj170404)supported by the Open Fund of Engineering Research Center of Catastrophic Prophylaxis and Treatment of Road and Traffic Safety of Ministry of Education(Changsha University of Science&Technology),ChinaProject(CX2018B527)supported by the Hunan Provincial Innovation Foundation for Postgraduate,ChinaProject(2018-025)supported by the Training Program for High-level Technical Personnel in Transportation Industry,China。
文摘To achieve durability of the embankment in southern China,a method to control the change of moisture content with the cushion and cover was proposed.A finite element model of cushion and cover considering different materials and thicknesses for a typical embankment was built,and 20 numerical analyses of transient seepage in the embankment were simulated.The results show that the sand cushion effectively blocks the effect of groundwater capillary rise and the minimum thickness of the sand cushion is 75 cm without considering the atmospheric environment.With the combination of sand cushion and clay cover,as the thickness of the clay cover increases,the duration time of the moisture content from the initial to relative equilibrium state increases,but the equilibrium moisture content is the same as that of the original embankment.Besides,with the combination of the sand cushion and sand cover,the moisture content inside the embankment remains the same,which is consistent with the optimum moisture content during construction.The combination of 75 cm sand cushion and 30 cm sand cover is a very effective method to block groundwater and atmospheric environment,and achieve the control of the humidity stability of the embankment in southern China.
基金supported by the Program for Liaoning Excellent Talents in University of China(LJQ2014013)the Liaoning Natural Science Foundation of China(2015020066)
文摘This study proposes a new nonlinear tracking control method with safe angular velocity constraints for a cushion robot. A fuzzy path planning algorithm is investigated and a realtime desired motion path of obstacle avoidance is obtained. The angular velocity is constrained by the controller, so the planned path guarantees the safety of users. According to Lyapunov theory, the controller is designed to maintain stability in terms of solutions of linear matrix inequalities and the controller's performance with safe angular velocity constraints is derived.The simulation and experiment results confirm the effectiveness of the proposed method and verify that the angular velocity of the cushion robot provided safe motion with obstacle avoidance.
基金supported by grants from the National Key Research and Development Program of China (grant no. 2017YFC0505200)the Major Program of National Natural Science Foundation of China (grant no. 31590823) to H Sunthe Natural Science Foundation of China (Grant no. 31500185 to JG Chen, 31470321 to Y Yang)
文摘Cushion species occur in nearly all alpine environments worldwide. In past decades, the adaptive and ecosystem-engineering roles of such highly specialized life forms have been well studied. However, the adaptive strategies responsible for cushion species reproductive success and maintenance in severe alpine habitats remain largely unclear. In this study, we reviewed the current understanding of reproductive strategies and population persistence in alpine cushion species. We then present a preliminary case study on the sexual reproduction of Arenaria polytrichoides(Caryophyllaceae), a typical cushion species inhabiting high elevations of the Himalaya Hengduan Mountains, which is a hotspot for diversification of cushion species. Finally, we highlight the limitations of our current understanding of alpine cushion species reproduction and propose future directions for study.
基金the National Natural Science Foundation of China(Grant Nos.51971188 and 51071134)the Science and Technology Major Project of Hunan Province(Grant No.2019GK 1012)+1 种基金Huxiang High-Level Talent Gathering Program of Hunan Province-In novative team(Grant No.2019RS1059)the Degree and Postgraduate Education Reform Project of Hunan Province(Grant No,CX20190493),All of this support is gratefully acknowledged.
文摘This paper uses the discrete element method to model the size and cushion effects during single-particle crushing tests.We propose simplified numerical modeling to examine the effects of particle size and coordination number on particle breakage behavior.We validate the proposed modeling by comparing the numerical results with the experimental data reported in the literature,in terms of the variability of particle tensile strength and axial force-displacement responses.Based on the numerical results,it is clear that a larger particle size entails a higher tensile strength with a larger discreteness.In addition,the characteristic tensile strength increases linearly with an increasing coordination number.Moreover,smaller particles are more susceptible to the cushion effect than larger particles.The numerical results also indicate that an increasing coordination number induces a more ductile mode of failure.Based on these results,we propose an empirical equation for calculating tensile strength,incorporating both the cushion effect and the size effect.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFC0505200,to Hang Sun)the Major Program of National Natural Science Foundation of China(Grant No.31590823,to Hang Sun)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA20050203,to Hang Sun)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB15020302,to Jianqiang Su)the Yunnan Applied Basic Research Project(Grant No.2018FA015,to Yang Yang)
文摘Positive associations between alpine cushion plants and other species have been extensively studied.However,almost all studies have focused on the associations between macrofauna.Studies that have investigated positive associations between alpine cushion plants and rhizospheric microbes have been limited to the vegetation growing season.Here,we asked whether the positive effects that alpine cushion plants confer on rhizospheric microbe communities vary with seasons.We assessed seasonal variations in the bacterial diversity and composition in rhizosphere of two alpine cushion plants and surrounding bare ground by employing a high throughput sequencing method targeting the V3 region of bacterial 16 S rRNA genes.Soil properties of the rhizosphere and the bare ground were also examined.We found that cushion rhizospheres harbored significantly more C,N,S,ammonia nitrogen,and soil moisture than the bare ground.Soil properties in cushion rhizospheres were not notably different,except for soil pH.Bacterial diversities within the same microhabitats did not vary significantly with seasons.We concluded that alpine cushion plants had positive effects on the rhizospheric bacterial communities,even though the strength of the effect varied in different cushion species.Cushion species and the soil sulfur content were probably the major factors driving the spatial distribution and structure of soil bacterial communities in the alpine communities dominated by cushion plants.
文摘AIM: To describe the anal cushion lifting(ACL) method with preliminary clinical results. METHODS: Between January to September 2007, 127 patients who received ACL method for hemorrhoid was investigated with informed consent. In this study, three surgeons who specialized in anorectal surgery performed the procedures. Patients with grade two or more severe hemorrhoids according to Goligher's classification were considered to be indicated for surgery. The patients were given the choice to undergo either the ACL method or theligation and excision method. ACL method is an original technique for managing hemorrhoids without excision. After dissecting the anal cushion from the internal sphincter muscle, the anal cushion was lifted to oral side and ligated at the proper position. Clinical characteristics and outcomes of patients were recorded including complications after surgery. RESULTS: A total of 127 patients were enrolled. Their median age was 42(19-84) years, and 74.8% were female. In addition, more than 99% of the patients had grade 3 or worse hemorrhoids. The median followup period was 26(0-88) mo, and the median operative time was 15(4-30) min. After surgery, analgesics were used for a median period of three days(0-21). Pain control was achieved using extra-oral analgesic drugs, although some patients required intravenous injections of analgesic drugs. The median duration of the patients' postoperative hospital stay was 7(2-13) d. A total of 10 complications(7.9%) occurred. Bleeding was observed in one patient and was successfully controlled with manual compression. Urinary retention occurred in 6 patients, but it disappeared spontaneously in all cases. Recurrent hemorrhoids developed in 3 patients after 36, 47, and 61 mo, respectively. No anal stenosis or persistent anal pain occurred. CONCLUSION: We consider that the ACL method might be better than all other current methods for managing hemorrhoids.
