A novel block–particle discrete-element simulation method that matches the double medium of overlying rock(OLR)and loose layer(LSL)in coal mining is developed in this study.This method achieves the collaborative fail...A novel block–particle discrete-element simulation method that matches the double medium of overlying rock(OLR)and loose layer(LSL)in coal mining is developed in this study.This method achieves the collaborative failure characteristics of mining damage under the conduction of double media between the OLR and LSL by combining the self-weight stress loading of the LSL and the breakage morphology of the bedrock top.Based on this,the conduction law of high-strength mining damage in the double medium in a western mining area is simulated and analyzed.The combining effect of the OLR breakage morphology and LSL characteristics on the surface-subsidence characteristics is analyzed and verified based on on-site measurements.The results indicate that the OLR is guided by the“double-control layer and thick-soft rock buffer layer”and shows“grouping subsidence”,whereas the surface forms collaborative subsidence with the thick-soft rock buffer layer.In the ultra-full mining stage,the surface presents an“asymmetric inverted trapezoidal”subsidence trough shape.The simulation results agree well the on-site measurements in terms of the surface-subsidence and bedrock-subsidence coefficients.The proposed simulation method provides a scientific approach for investigating the micro-conduction mechanism of mining damage under the effect of high-strength mining in western mining areas.It will benefit future investigations pertaining to the characteristics of OLR breakage and surface subsidence under conditions such as LSL thickness and proportion.展开更多
Sand production and high water content in oil wells are two major challenges that restrict high and stable production in loose sandstone reservoirs.In this paper,nano SiO_(2),coupling agent triethoxysilane,phenolic re...Sand production and high water content in oil wells are two major challenges that restrict high and stable production in loose sandstone reservoirs.In this paper,nano SiO_(2),coupling agent triethoxysilane,phenolic resin and n-octanol were used to synthesize the main agent SCA-2.Hexamethylenetetramine and vinyl carbonate were selected to prepare the curing agent YGA-1,which was then compounded with SCA-2 to develop a sand fixation and water plugging system.Firstly,single-factor experiments were conducted to determine the optimal concentrations of SCA-2 and YGA-1,subsequently,the system’s sand fixation and water blocking performance were evaluated.Finally,a pilot test was carried out in the mining site.Experimental results showed that the optimal formula composition of the system was 10%SCA-2+5%YGA-1.The gelation time of the system was 180 minutes and the viscosity after gelation could reach 108.4 mPa·s.When the dosage of the drug system was 0.6 PV,the sand production rate remained below 0.08%.Dual-tube parallel experiments showed that the sand fixation and water plugging system had a water flow channel plugging rate of 87.5%,while the oil flow channel plugging rate was only 11.3%,indicating minimal damage to the oil-bearing reservoir.The field test showed that after the measures taken in Well M of X oilfield,the sand free oil recovery period exceeded 360 days,the water content decreased by 5.0%and the cumulative oil production increased by 7092 m^(3).This study provides new ideas for efficient development of loose sandstone reservoirs.展开更多
In 2024,China’s economy gradually trended towards recovery from the COVID-19 pandemic.According to official data released by the National Bureau of Statistics on January 17,preliminary estimates show China’s gross d...In 2024,China’s economy gradually trended towards recovery from the COVID-19 pandemic.According to official data released by the National Bureau of Statistics on January 17,preliminary estimates show China’s gross domestic product(GDP)at nearly 134 trillion yuan(US$18.7 trillion)in 2024,an increase of 5.0 percent over the previous year at constant prices.展开更多
Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogen...Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogeneous strata,with limited research conducted on the upper loose and lower dense strata.Active instability tests are conducted in this study,in concert with the digital image correlation(DIC)technique,to investigate the effects of different water pressure ratios in upper loose and lower dense water-rich strata.The accuracy of these model tests is verified using numerical simulations.The results indicate that as water pressure ratio decreases,there is an increase in both the peak displacement of surface settlement and the seepage path range of water ahead of the excavation face expands.In contrast,decreasing water pressure ratio will break the limit equilibrium state of the strata faster,cause the earth pressure on the cutterhead to change more rapidly,and increase the instability range of the strata.展开更多
[Objective] The research aimed to establish the cell suspension culture system of Pinellia ternate.[Method] The petiole of Pinellia ternate was as the explant.The orthogonal test was used to study the influences of fo...[Objective] The research aimed to establish the cell suspension culture system of Pinellia ternate.[Method] The petiole of Pinellia ternate was as the explant.The orthogonal test was used to study the influences of four plant growth substances（2,4-D,NAA,picloram and KT）and their mixture ratios on the formation of loose callus.[Result] The induction effect of 2,4-D and picloram on the petiole callus of Pinellia ternate was the most significant.Then,the second ones were KT and NAA.The optimal medium which induced Pinellia ternate petiole to form the loose callus was MS＋0.5 mg/L of 2,4-D＋1.0 mg/L of NAA＋1.0 mg/L of picloram＋1.5 mg/L of KT.[Conclusion] The research laid the foundation for extracting the active ingredient from the cell suspension of Pinellia ternate and producing the artificial seed.展开更多
为保证虚拟手术系统中的网格质量,提出一种基于Loose r sample理论的快速表面网格重建算法。记录满足Loose r sample采样定理的点集,用以描述物体的轮廓。通过约束Delaunay方法对该点集进行三角化,标记顶点和Delaunay单元,重构新的网格...为保证虚拟手术系统中的网格质量,提出一种基于Loose r sample理论的快速表面网格重建算法。记录满足Loose r sample采样定理的点集,用以描述物体的轮廓。通过约束Delaunay方法对该点集进行三角化,标记顶点和Delaunay单元,重构新的网格。实验结果表明,该算法能够保证生成网格的质量,简化仿真复杂度。展开更多
In terms of the common practice of professional grading and loose-leaf purchasing technology, the advantages of these technologies were demonstrated. The problems and proposals of the professional grading leaves purch...In terms of the common practice of professional grading and loose-leaf purchasing technology, the advantages of these technologies were demonstrated. The problems and proposals of the professional grading leaves purchasing model were also summarized and analyzed, so as to provide practical experiences for fur- ther promotion of loose-leaf purchasing.展开更多
We determined the effects of adhesive type and loose tenon dimensions （length and thickness） on bending strength of T-shaped mor- tise and loose-tenon joints. Polyvinyl acetate （PVAc） and two-component polyuretha...We determined the effects of adhesive type and loose tenon dimensions （length and thickness） on bending strength of T-shaped mor- tise and loose-tenon joints. Polyvinyl acetate （PVAc） and two-component polyurethane （PU） adhesives were used to construct joint specimens. The bending moment capacity of joints increased significantly with increased length and thickness of the loose tenon. Bending moment capacity of joints constructed with PU adhesive was approximately 13% higher than for joints constructed with PVAc adhesive. We developed a predictive equation as a function of adhesive type and loose tenon dimensions to estimate the strength of the joints constructed of oriental beech （Fagus orientalis L.） under uniaxial bending load.展开更多
Loose deposits, rainfall and topography are three key factors that triggering debris flows.However, few studies have investigated the effects of loose deposits on the whole debris flow process.On June 28, 2012, a cata...Loose deposits, rainfall and topography are three key factors that triggering debris flows.However, few studies have investigated the effects of loose deposits on the whole debris flow process.On June 28, 2012, a catastrophic debris flow occurred in the Aizi Valley, resulting in 40 deaths.The Aizi Valley is located in the Lower Jinsha River,southwestern Sichuan Province, China. The Aizi Valley debris flow has been selected as a case for addressing loose deposits effects on the whole debris flow process through remote sensing, field investigation and field experiments. Remote sensing interpretation and laboratory experiments were used to obtain the distribution and characteristics of the loose deposits, respectively. A field experiment was conducted to explore the mechanics of slope debris flows, and another field investigation was conducted to obtain the processes of debris flow formation, movement and amplification. The results showed that loose deposits preparation, slope debris flow initiation,gully debris flow confluence and valley debris flow amplification were dominated by the loose deposits.Antecedent droughts and earthquake activities may have increased the potential for loose soil sources in the Aizi Valley, which laid the foundation for debris flow formation. Slope debris flow initiated under rainfall, and the increase in the water content as well as the pore water pressure of the loose deposits were the key factors affecting slope failure. The nine gully debris flows converged in the valley, and the peak discharge was amplified 3.3 times due to a blockage and outburst caused by a large boulder. The results may help in predicting and assessing regional debris flows in dry-hot and seismic-prone areas based on loose deposits, especially considering large boulders.展开更多
A large amount of loose debris materials were deposited on the slope of mountainous areas after the 2008 Ms 8.0 Wenchuan earthquake. During and after the earthquake, these loose debris deposits collapsed and slide int...A large amount of loose debris materials were deposited on the slope of mountainous areas after the 2008 Ms 8.0 Wenchuan earthquake. During and after the earthquake, these loose debris deposits collapsed and slide into valleys or rivers, changing river sediment supply condition and channel morphology. To investigate the mechanisms of granular flow and deposition, the dynamics of slope failure and sediment transportation in typical mountainous rivers of different intersection angles were analyzed with a coupling model of Computational Fluid Dynamics and Discrete Element Method(CFD-DEM). The numerical results show that the change of intersection angle between the granular flow flume and the river channel can affect the deposit geometry and the fluid flow field significantly. As the intersection angle increases, the granular velocity perpendicular to the river channel increases, while the granular velocity parallel to the river channel decreases gradually. Compared to the test of dry granular flow, the CFD-DEM coupling tests show much higher granular velocity and larger volume of sediments entrained in the river. Due to the river flow, particles located at the edge of the deposition will move downstream gradually and the main section of sediments deposition moves from the center to the edge of the river channel. As a result, sediment supply in the downstream river will distribute unevenly. Under the erosion of fluid flow, the proportion of fine particles increases, while the proportion of coarse particles decreases gradually in the sediment deposition. The build-up of accumulated sediment mass will cause a significant increase in water level in the river channel, thus creating serious flooding hazard in mountainous rivers.展开更多
This article presents an innovative method of bio-mediated soil improvement for increasing the shear strength of loose sand.The improvement is realized by mixing the loose sand with the inoculum of Rhizopus oligosporu...This article presents an innovative method of bio-mediated soil improvement for increasing the shear strength of loose sand.The improvement is realized by mixing the loose sand with the inoculum of Rhizopus oligosporus,a kind of fungus widely used in food industry for making Indonesian tempeh.The objective of this article is to investigate the performance and mechanism of mixing tempeh inoculum as a binding agent of loose sand particles.The inoculum dosage,water content of loose sand,and curing time were examined for identifying the increment of unconfined compressive strength(q_u)of the samples.The results showed that q_u of the treated samples increased when the inoculum dosage was elevated.It shows that 5.24%inoculum could yield 68 kPa of q_u,and 5%water content and 3 d curing time produced the maximum q_u.Moreover,the mechanism of hypha and mycelium in binding the soil particles was clearly observed using a digital microscope and scanning electron microscope.展开更多
Fractures of the talus are rare in children.A high index of suspicion is needed to avoid missing such an injury,which is not an uncommon occurrence especially with undisplaced fractures.We present an unusual case of a...Fractures of the talus are rare in children.A high index of suspicion is needed to avoid missing such an injury,which is not an uncommon occurrence especially with undisplaced fractures.We present an unusual case of an undisplaced talar neck fracture in a five-year-old child leading to a delayed presentation of a symptomatic osteochondral loose body in the ankle joint.To our knowledge there are no reports in the literature of osteochondral loose bodies occurring in conjunction with an associated undisplaced talar neck fracture in either children or adults.The loose body was removed using anterior ankle arthroscopy.The child had an uneventful post operative recovery and regained full range of movement and function of his ankle joint and was discharged at one year follow-up.We aim to highlight the need to have a low threshold to further evaluate symptomatic children after fracture healing of an undisplaced talar neck fracture for a possible associated loose bodyin the ankle joint.展开更多
We studied the effect of loose tenon dimensions on stress and strain distributions in T-shaped mortise and loose tenon （M＆amp;LT） furni-ture joints under uniaxial bending loads, and determined the effects of loose ...We studied the effect of loose tenon dimensions on stress and strain distributions in T-shaped mortise and loose tenon （M＆amp;LT） furni-ture joints under uniaxial bending loads, and determined the effects of loose tenon length （30, 45, 60, and 90 mm） and loose tenon thickness （6 and 8 mm） on bending moment capacity of M＆amp;LT joints constructed with polyvinyl acetate （PVAc） adhesive. Stress and strain distributions in joint elements were then estimated for each joint using ANSYS finite element （FE） software. The bending moment capacity of joints increased significantly with thickness and length of the tenon. Based on the FE analysis results, under uniaxial bending, the highest shear stress values were obtained in the middle parts of the tenon, while the highest shear elastic strain values were estimated in glue lines between the tenon sur-faces and walls of the mortise. Shear stress and shear elastic strain values in joint elements generally increased with tenon dimensions and corre-sponding bending moment capacities. There was consistency between predicted maximum shear stress values and failure modes of the joints.展开更多
A loose coupling method is used to solve the electromagnetic tube bulging.ANSYS/EMAG is used to model the time varying electromagnetic field with the discharge current used as excitation,in order to obtain the radial ...A loose coupling method is used to solve the electromagnetic tube bulging.ANSYS/EMAG is used to model the time varying electromagnetic field with the discharge current used as excitation,in order to obtain the radial and axial magnetic pressure acting on the tube,the magnetic pressure is then used as boundary conditions to model the high velocity deformation of tube with DYNAFORM,The radial magnetic pressure on the tube decreases from the center to the tube end,axial magnetic pressure is greater near the location equal to the coil height and slight in the other region.The radial displacement of deformed workpicces is distributed uniformly near the tube center and decreases from the center to the end;Deformation from the location equal to coil height to the tube end is little.This distribution is consistent with the distribution of radial pressure;Effect of the axial magnetic pressure on deformation can be ignored,The calculated results show well agreements with the experimental results.展开更多
An effective method for preventing spontaneous combustion of coal stockpiles on the ground is to control the air-flow in loose coal. In order to determine and predict accurately oxygen concentrations and temperatures ...An effective method for preventing spontaneous combustion of coal stockpiles on the ground is to control the air-flow in loose coal. In order to determine and predict accurately oxygen concentrations and temperatures within coal stockpiles, it is vital to obtain information of self-heating conditions and tendencies of spontaneous coal combustion. For laboratory conditions, we designed our own experimental equipment composed of a control-heating system, a coal column and an oxygen concentration and temperature monitoring system, for simulation of spontaneous combustion of block coal （13-25 mm） covered with fine coal （0-3 mm）. A BP artificial neural network （ANN） with 150 training samples was gradually established over the course of our experiment. Heating time, relative position of measuring points, the ratio of fine coal thickness, artificial density, voidage and activation energy were selected as input variables and oxygen concentration and temperature of coal column as output variables. Then our trained network was applied to predict the trend on the untried experimental data. The results show that the oxygen concentration in the coal column could be reduced below the minimum still able to induce spontaneous combustion of coal - 6% by covering the coal pile with fine coal, which would meet the requirement to prevent spontaneous combustion of coal stockpiles. Based on the prediction of this ANN, the average errors of oxygen concentration and temperature were respectively 0.5% and 7 ℃, which meet actual tolerances. The implementation of the method would provide a practical guide in understanding the course of self-heating and spontaneous combustion of coal stockpiles.展开更多
In this paper,the nonlinear dynamics of a curved pipe is investigated in the case of principal parametric resonance due to pulsating flow and impact with loose supports.The coupled in-plane and out-of-plane governing ...In this paper,the nonlinear dynamics of a curved pipe is investigated in the case of principal parametric resonance due to pulsating flow and impact with loose supports.The coupled in-plane and out-of-plane governing equations with the consideration of von Karman geometric nonUnearity are presented and discretized via the differential quadrature method（DQM）.The nonlinear dynamic responses are calculated numerically to demonstrate the influence of pulsating frequency.Finally,the impact is taken into consideration.The influence of clearance on frettingwear damage,such as normal work rate,contact ratio and impact force level,is demonstrated.展开更多
Random loose packing is the minimum-density granular packing which can maintain mechanical stability. In this study, x-ray tomography is used to investigate the internal structure of an isotropically prepared random l...Random loose packing is the minimum-density granular packing which can maintain mechanical stability. In this study, x-ray tomography is used to investigate the internal structure of an isotropically prepared random loose packing through a special apparatus to minimize the effect of gravity. It is found that the minimum packing density is around 0.587. The microscopic structural analysis of the packing is also carried out.展开更多
Failure of loose gully deposits under the effect of rainfall contributes to the potential risk of debris flow.In the past decades, researches on hydraulic mechanism and time-dependent characteristics of loosedeposits ...Failure of loose gully deposits under the effect of rainfall contributes to the potential risk of debris flow.In the past decades, researches on hydraulic mechanism and time-dependent characteristics of loosedeposits failure are frequently reported, however adequate measures for reducing debris flow are notavailable practically. In this context, a time-dependent model was established to determine the changesof water table of loose deposits using hydraulic and topographic theories. In addition, the variation inwater table with elapsed time was analyzed. The formulas for calculating hydrodynamic and hydrostaticpressures on each strip and block unit of deposit were proposed, and the slope stability and failure risk ofthe loose deposits were assessed based on the time-dependent hydraulic characteristics of establishedmodel. Finally, the failure mechanism of deposits based on infinite slope theory was illustrated, with anexample, to calculate sliding force, anti-sliding force and residual sliding force applied to each slice. Theresults indicate that failure of gully deposits under the effect of rainfall is the result of continuouslyincreasing hydraulic pressure and water table. The time-dependent characteristics of loose depositfailure are determined by the factors of hydraulic properties, drainage area of interest, rainfall pattern,rainfall duration and intensity.展开更多
基金support for this work is provided by the National Key R&D Program of China(2023YFC3012101)the National Natural Science Foundation of China(52474161)the Fundamental Research Funds for the Central Universities(2024ZKPYNY01).
文摘A novel block–particle discrete-element simulation method that matches the double medium of overlying rock(OLR)and loose layer(LSL)in coal mining is developed in this study.This method achieves the collaborative failure characteristics of mining damage under the conduction of double media between the OLR and LSL by combining the self-weight stress loading of the LSL and the breakage morphology of the bedrock top.Based on this,the conduction law of high-strength mining damage in the double medium in a western mining area is simulated and analyzed.The combining effect of the OLR breakage morphology and LSL characteristics on the surface-subsidence characteristics is analyzed and verified based on on-site measurements.The results indicate that the OLR is guided by the“double-control layer and thick-soft rock buffer layer”and shows“grouping subsidence”,whereas the surface forms collaborative subsidence with the thick-soft rock buffer layer.In the ultra-full mining stage,the surface presents an“asymmetric inverted trapezoidal”subsidence trough shape.The simulation results agree well the on-site measurements in terms of the surface-subsidence and bedrock-subsidence coefficients.The proposed simulation method provides a scientific approach for investigating the micro-conduction mechanism of mining damage under the effect of high-strength mining in western mining areas.It will benefit future investigations pertaining to the characteristics of OLR breakage and surface subsidence under conditions such as LSL thickness and proportion.
文摘Sand production and high water content in oil wells are two major challenges that restrict high and stable production in loose sandstone reservoirs.In this paper,nano SiO_(2),coupling agent triethoxysilane,phenolic resin and n-octanol were used to synthesize the main agent SCA-2.Hexamethylenetetramine and vinyl carbonate were selected to prepare the curing agent YGA-1,which was then compounded with SCA-2 to develop a sand fixation and water plugging system.Firstly,single-factor experiments were conducted to determine the optimal concentrations of SCA-2 and YGA-1,subsequently,the system’s sand fixation and water blocking performance were evaluated.Finally,a pilot test was carried out in the mining site.Experimental results showed that the optimal formula composition of the system was 10%SCA-2+5%YGA-1.The gelation time of the system was 180 minutes and the viscosity after gelation could reach 108.4 mPa·s.When the dosage of the drug system was 0.6 PV,the sand production rate remained below 0.08%.Dual-tube parallel experiments showed that the sand fixation and water plugging system had a water flow channel plugging rate of 87.5%,while the oil flow channel plugging rate was only 11.3%,indicating minimal damage to the oil-bearing reservoir.The field test showed that after the measures taken in Well M of X oilfield,the sand free oil recovery period exceeded 360 days,the water content decreased by 5.0%and the cumulative oil production increased by 7092 m^(3).This study provides new ideas for efficient development of loose sandstone reservoirs.
文摘In 2024,China’s economy gradually trended towards recovery from the COVID-19 pandemic.According to official data released by the National Bureau of Statistics on January 17,preliminary estimates show China’s gross domestic product(GDP)at nearly 134 trillion yuan(US$18.7 trillion)in 2024,an increase of 5.0 percent over the previous year at constant prices.
基金supported by the National Natural Science Foundation of China(No.51978019)the Natural Science Foundation of Beijing Municipality(No.8222004),China.
文摘Maintaining the stability of the excavation face is key for ensuring the safety of underwater shield tunnel construction.However,the majority of current studies on the stability of excavation face focus on the homogeneous strata,with limited research conducted on the upper loose and lower dense strata.Active instability tests are conducted in this study,in concert with the digital image correlation(DIC)technique,to investigate the effects of different water pressure ratios in upper loose and lower dense water-rich strata.The accuracy of these model tests is verified using numerical simulations.The results indicate that as water pressure ratio decreases,there is an increase in both the peak displacement of surface settlement and the seepage path range of water ahead of the excavation face expands.In contrast,decreasing water pressure ratio will break the limit equilibrium state of the strata faster,cause the earth pressure on the cutterhead to change more rapidly,and increase the instability range of the strata.
基金Supported by National Natural Science Fund Item(30973963)Anhui Natural Science Fund Item(090413252)+1 种基金Natural Science ResearchKey Project of Anhui Provincial University(KJ2009A160)"Key Labora-tory Project"of Plant Resource and Biology(KLPRB200914)~~
文摘[Objective] The research aimed to establish the cell suspension culture system of Pinellia ternate.[Method] The petiole of Pinellia ternate was as the explant.The orthogonal test was used to study the influences of four plant growth substances（2,4-D,NAA,picloram and KT）and their mixture ratios on the formation of loose callus.[Result] The induction effect of 2,4-D and picloram on the petiole callus of Pinellia ternate was the most significant.Then,the second ones were KT and NAA.The optimal medium which induced Pinellia ternate petiole to form the loose callus was MS＋0.5 mg/L of 2,4-D＋1.0 mg/L of NAA＋1.0 mg/L of picloram＋1.5 mg/L of KT.[Conclusion] The research laid the foundation for extracting the active ingredient from the cell suspension of Pinellia ternate and producing the artificial seed.
文摘为保证虚拟手术系统中的网格质量,提出一种基于Loose r sample理论的快速表面网格重建算法。记录满足Loose r sample采样定理的点集,用以描述物体的轮廓。通过约束Delaunay方法对该点集进行三角化,标记顶点和Delaunay单元,重构新的网格。实验结果表明,该算法能够保证生成网格的质量,简化仿真复杂度。
文摘In terms of the common practice of professional grading and loose-leaf purchasing technology, the advantages of these technologies were demonstrated. The problems and proposals of the professional grading leaves purchasing model were also summarized and analyzed, so as to provide practical experiences for fur- ther promotion of loose-leaf purchasing.
文摘We determined the effects of adhesive type and loose tenon dimensions （length and thickness） on bending strength of T-shaped mor- tise and loose-tenon joints. Polyvinyl acetate （PVAc） and two-component polyurethane （PU） adhesives were used to construct joint specimens. The bending moment capacity of joints increased significantly with increased length and thickness of the loose tenon. Bending moment capacity of joints constructed with PU adhesive was approximately 13% higher than for joints constructed with PVAc adhesive. We developed a predictive equation as a function of adhesive type and loose tenon dimensions to estimate the strength of the joints constructed of oriental beech （Fagus orientalis L.） under uniaxial bending load.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41861134008 and 41601476)the National Key Research and Development Program of China (Grant No. 2018YFC1505202)the 135 Strategic Program of the IMHE, CAS (Grant No. SDS-1351705)
文摘Loose deposits, rainfall and topography are three key factors that triggering debris flows.However, few studies have investigated the effects of loose deposits on the whole debris flow process.On June 28, 2012, a catastrophic debris flow occurred in the Aizi Valley, resulting in 40 deaths.The Aizi Valley is located in the Lower Jinsha River,southwestern Sichuan Province, China. The Aizi Valley debris flow has been selected as a case for addressing loose deposits effects on the whole debris flow process through remote sensing, field investigation and field experiments. Remote sensing interpretation and laboratory experiments were used to obtain the distribution and characteristics of the loose deposits, respectively. A field experiment was conducted to explore the mechanics of slope debris flows, and another field investigation was conducted to obtain the processes of debris flow formation, movement and amplification. The results showed that loose deposits preparation, slope debris flow initiation,gully debris flow confluence and valley debris flow amplification were dominated by the loose deposits.Antecedent droughts and earthquake activities may have increased the potential for loose soil sources in the Aizi Valley, which laid the foundation for debris flow formation. Slope debris flow initiated under rainfall, and the increase in the water content as well as the pore water pressure of the loose deposits were the key factors affecting slope failure. The nine gully debris flows converged in the valley, and the peak discharge was amplified 3.3 times due to a blockage and outburst caused by a large boulder. The results may help in predicting and assessing regional debris flows in dry-hot and seismic-prone areas based on loose deposits, especially considering large boulders.
基金supported by the National Natural Science Foundation of China (51579163 and 51639007)the National Key R&D Program of China (2017YFC1502504 and 2016YFC0402304)
文摘A large amount of loose debris materials were deposited on the slope of mountainous areas after the 2008 Ms 8.0 Wenchuan earthquake. During and after the earthquake, these loose debris deposits collapsed and slide into valleys or rivers, changing river sediment supply condition and channel morphology. To investigate the mechanisms of granular flow and deposition, the dynamics of slope failure and sediment transportation in typical mountainous rivers of different intersection angles were analyzed with a coupling model of Computational Fluid Dynamics and Discrete Element Method(CFD-DEM). The numerical results show that the change of intersection angle between the granular flow flume and the river channel can affect the deposit geometry and the fluid flow field significantly. As the intersection angle increases, the granular velocity perpendicular to the river channel increases, while the granular velocity parallel to the river channel decreases gradually. Compared to the test of dry granular flow, the CFD-DEM coupling tests show much higher granular velocity and larger volume of sediments entrained in the river. Due to the river flow, particles located at the edge of the deposition will move downstream gradually and the main section of sediments deposition moves from the center to the edge of the river channel. As a result, sediment supply in the downstream river will distribute unevenly. Under the erosion of fluid flow, the proportion of fine particles increases, while the proportion of coarse particles decreases gradually in the sediment deposition. The build-up of accumulated sediment mass will cause a significant increase in water level in the river channel, thus creating serious flooding hazard in mountainous rivers.
基金the research funding provided by Ikatan Alumni Teknik Sipil(IATS)UnparUniversitas Katolik Parahyangan.
文摘This article presents an innovative method of bio-mediated soil improvement for increasing the shear strength of loose sand.The improvement is realized by mixing the loose sand with the inoculum of Rhizopus oligosporus,a kind of fungus widely used in food industry for making Indonesian tempeh.The objective of this article is to investigate the performance and mechanism of mixing tempeh inoculum as a binding agent of loose sand particles.The inoculum dosage,water content of loose sand,and curing time were examined for identifying the increment of unconfined compressive strength(q_u)of the samples.The results showed that q_u of the treated samples increased when the inoculum dosage was elevated.It shows that 5.24%inoculum could yield 68 kPa of q_u,and 5%water content and 3 d curing time produced the maximum q_u.Moreover,the mechanism of hypha and mycelium in binding the soil particles was clearly observed using a digital microscope and scanning electron microscope.
文摘Fractures of the talus are rare in children.A high index of suspicion is needed to avoid missing such an injury,which is not an uncommon occurrence especially with undisplaced fractures.We present an unusual case of an undisplaced talar neck fracture in a five-year-old child leading to a delayed presentation of a symptomatic osteochondral loose body in the ankle joint.To our knowledge there are no reports in the literature of osteochondral loose bodies occurring in conjunction with an associated undisplaced talar neck fracture in either children or adults.The loose body was removed using anterior ankle arthroscopy.The child had an uneventful post operative recovery and regained full range of movement and function of his ankle joint and was discharged at one year follow-up.We aim to highlight the need to have a low threshold to further evaluate symptomatic children after fracture healing of an undisplaced talar neck fracture for a possible associated loose bodyin the ankle joint.
文摘We studied the effect of loose tenon dimensions on stress and strain distributions in T-shaped mortise and loose tenon （M＆amp;LT） furni-ture joints under uniaxial bending loads, and determined the effects of loose tenon length （30, 45, 60, and 90 mm） and loose tenon thickness （6 and 8 mm） on bending moment capacity of M＆amp;LT joints constructed with polyvinyl acetate （PVAc） adhesive. Stress and strain distributions in joint elements were then estimated for each joint using ANSYS finite element （FE） software. The bending moment capacity of joints increased significantly with thickness and length of the tenon. Based on the FE analysis results, under uniaxial bending, the highest shear stress values were obtained in the middle parts of the tenon, while the highest shear elastic strain values were estimated in glue lines between the tenon sur-faces and walls of the mortise. Shear stress and shear elastic strain values in joint elements generally increased with tenon dimensions and corre-sponding bending moment capacities. There was consistency between predicted maximum shear stress values and failure modes of the joints.
文摘A loose coupling method is used to solve the electromagnetic tube bulging.ANSYS/EMAG is used to model the time varying electromagnetic field with the discharge current used as excitation,in order to obtain the radial and axial magnetic pressure acting on the tube,the magnetic pressure is then used as boundary conditions to model the high velocity deformation of tube with DYNAFORM,The radial magnetic pressure on the tube decreases from the center to the tube end,axial magnetic pressure is greater near the location equal to the coil height and slight in the other region.The radial displacement of deformed workpicces is distributed uniformly near the tube center and decreases from the center to the end;Deformation from the location equal to coil height to the tube end is little.This distribution is consistent with the distribution of radial pressure;Effect of the axial magnetic pressure on deformation can be ignored,The calculated results show well agreements with the experimental results.
文摘An effective method for preventing spontaneous combustion of coal stockpiles on the ground is to control the air-flow in loose coal. In order to determine and predict accurately oxygen concentrations and temperatures within coal stockpiles, it is vital to obtain information of self-heating conditions and tendencies of spontaneous coal combustion. For laboratory conditions, we designed our own experimental equipment composed of a control-heating system, a coal column and an oxygen concentration and temperature monitoring system, for simulation of spontaneous combustion of block coal （13-25 mm） covered with fine coal （0-3 mm）. A BP artificial neural network （ANN） with 150 training samples was gradually established over the course of our experiment. Heating time, relative position of measuring points, the ratio of fine coal thickness, artificial density, voidage and activation energy were selected as input variables and oxygen concentration and temperature of coal column as output variables. Then our trained network was applied to predict the trend on the untried experimental data. The results show that the oxygen concentration in the coal column could be reduced below the minimum still able to induce spontaneous combustion of coal - 6% by covering the coal pile with fine coal, which would meet the requirement to prevent spontaneous combustion of coal stockpiles. Based on the prediction of this ANN, the average errors of oxygen concentration and temperature were respectively 0.5% and 7 ℃, which meet actual tolerances. The implementation of the method would provide a practical guide in understanding the course of self-heating and spontaneous combustion of coal stockpiles.
文摘In this paper,the nonlinear dynamics of a curved pipe is investigated in the case of principal parametric resonance due to pulsating flow and impact with loose supports.The coupled in-plane and out-of-plane governing equations with the consideration of von Karman geometric nonUnearity are presented and discretized via the differential quadrature method（DQM）.The nonlinear dynamic responses are calculated numerically to demonstrate the influence of pulsating frequency.Finally,the impact is taken into consideration.The influence of clearance on frettingwear damage,such as normal work rate,contact ratio and impact force level,is demonstrated.
基金supported by the Thirteenth Shanghai Jiao Tong University Students Innovation Practice Plan,China(Grant No.IPP13086)the National Natural Science Foundation of China(Grant Nos.11175121,11675110,and U1432111)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110073120073)
文摘Random loose packing is the minimum-density granular packing which can maintain mechanical stability. In this study, x-ray tomography is used to investigate the internal structure of an isotropically prepared random loose packing through a special apparatus to minimize the effect of gravity. It is found that the minimum packing density is around 0.587. The microscopic structural analysis of the packing is also carried out.
基金supported by the National Natural Science Foundation of China(Grant No.41202258)STS Project(Grant No.KFJ-EW-STS-094)+1 种基金Research Plan Project of China Railway Eryuan Engineering Group Co.,Ltd.(Grant No.13164196(13-15))the State Key Laboratory Project Fund of Geohazard Prevention and Geoenvironment Protection(Grant No.SKLGP2013K012)
文摘Failure of loose gully deposits under the effect of rainfall contributes to the potential risk of debris flow.In the past decades, researches on hydraulic mechanism and time-dependent characteristics of loosedeposits failure are frequently reported, however adequate measures for reducing debris flow are notavailable practically. In this context, a time-dependent model was established to determine the changesof water table of loose deposits using hydraulic and topographic theories. In addition, the variation inwater table with elapsed time was analyzed. The formulas for calculating hydrodynamic and hydrostaticpressures on each strip and block unit of deposit were proposed, and the slope stability and failure risk ofthe loose deposits were assessed based on the time-dependent hydraulic characteristics of establishedmodel. Finally, the failure mechanism of deposits based on infinite slope theory was illustrated, with anexample, to calculate sliding force, anti-sliding force and residual sliding force applied to each slice. Theresults indicate that failure of gully deposits under the effect of rainfall is the result of continuouslyincreasing hydraulic pressure and water table. The time-dependent characteristics of loose depositfailure are determined by the factors of hydraulic properties, drainage area of interest, rainfall pattern,rainfall duration and intensity.
