Turbulent flow field of the free jet with circular nozzle and wedged nozzles is measured using hot wire anemometry with resolution higher than the smallest turbulence time scale. Wavelet analysis is employed to perfor...Turbulent flow field of the free jet with circular nozzle and wedged nozzles is measured using hot wire anemometry with resolution higher than the smallest turbulence time scale. Wavelet analysis is employed to perform multi-scale decomposition of instantaneous turbulence fluctuating velocity signals, and the energy distribution of the turbulent multi-scale eddy structures over scales is studied using wavelet coefficients. Investigation of the multi-scale eddy structures of circular jet and various wedged jets reveals the transport of the energy of these wedged jets in the space from the axis to the side of the jet, as compared with the circular jet. Furthermore, not only the eddy structures at the wedge tines in the near field are crashed, but also the interactions such as eddy structure union and entrainment take place at different longitudinal and normal locations along with the development of the jets because of the existence of wedges.展开更多
Aim: The purpose of this study was to make a comparison between measured and calculated physical wedge dose distributions using the superposition algorithm. Settings and Design: The accurate determination of absorbed ...Aim: The purpose of this study was to make a comparison between measured and calculated physical wedge dose distributions using the superposition algorithm. Settings and Design: The accurate determination of absorbed dose is important radiotherapy because of the relatively steep sigmoidal dose response curves for both tumor control and normal-tissue damage. Materials and Methods: High-energy photons (6 and 10 MV) from Artiste Treatment System Linear Accelerator Machine, available at Alexandria Ayadi Al-Mostakbal Oncology Center, were used. Results and Discussion: The results showed that the difference between measured and calculated wedged isodose curves depends on field size, beam energy, and the angle of the used wedge. Conclusion: The results showed that the presence of a wedge alters the primary and scattered components generated by a linear accelerator and causes beam hardening in 6 and 10 MV. The beam hardening increased as the wedge angle increased.展开更多
BACKGROUND Wedged hepatic venous pressure(WHVP)is a crucial variable for accurately assessing the hepatic venous pressure gradient(HVPG)and is vital for the diagnosis and prognostic evaluation of patients with portal ...BACKGROUND Wedged hepatic venous pressure(WHVP)is a crucial variable for accurately assessing the hepatic venous pressure gradient(HVPG)and is vital for the diagnosis and prognostic evaluation of patients with portal hypertension(PH).AIM To investigate the anatomical characteristics of balloon-occluded hepatic venous angiography in patients with PH and analyze the relationship between the WHVP and portal venous pressure(PVP).METHODS This retrospective study included 877 patients with PH who met the inclusion criteria from January 2020 to June 2024.Routine and innovative hepatic venous angiography was performed during transjugular intrahepatic portosystemic shunt procedures to measure hepatic venous and PVPs.All patients'angiographic images were collected for analysis.The associations between WHVP and PVP in each group were analyzed via linear regression analysis,and a predictive model was established.RESULTS The 877 patients had a mean age of 52.6±13.0 years,with 582 males and 295 females.Patients were categorized into four groups on the basis of their anatomical structure.All groups showed strong correlations between WHVP and PVP.The regression coefficient between the WHVP and PVP in the hepatic right vein-portal venous angiography group was 0.884(P<0.05);in the hepatic right vein-accessory hepatic venous angiography group,it was 0.721(P<0.05);in the hepatic right vein-middle hepatic venous angiography group,it was 0.344(P<0.05);and in the hepatic right vein-nonangiography group,it was 0.293(P<0.05).CONCLUSION The presence and anatomical classification of hepatic venous collaterals are key factors influencing the relationship between WHVP with and PVP.Based on the different anatomical classifications of hepatic veins,WHVP can be used to estimate PVP,improving the accuracy of PVP prediction.展开更多
The Paleo-Pacific Plate stagnated in the mantle transition zone beneath northeast Asia during the Late Mesozoic,resulting in the eastern Asian big mantle wedge(BMW).However,its formation mechanism remains unclear.Here...The Paleo-Pacific Plate stagnated in the mantle transition zone beneath northeast Asia during the Late Mesozoic,resulting in the eastern Asian big mantle wedge(BMW).However,its formation mechanism remains unclear.Here,we analyzed elemental and isotopic compositions of 126-60 Ma intraplate basaltic rocks to map the mantle flow pattern and investigate the implications for the formation of the BMW.These rocks exhibit eastward an increase in Ba/Nb,Ba/La,^(87)Sr/^(86)Sr,and^(208)Pb/^(204)Pb ratios,while a decrease in Nb/Yb,Zr/Yb,Ta/Yb,and Nb/Nb*ratios,indicating mixing between the fertile mantle and the depleted mantle modified by slab material,implying the occurrence of trench-perpendicular mantle flow.The coeval mantle flow and formation of the BMW,the similar directions of mantle flow and Paleo-Pacific Plate subduction,and migration of basin depocenters indicate trench-perpendicular mantle flow was a key factor in the formation of the BMW.Moreover,these basaltic rocks have elevatedδ^(66)Zn values(0.22‰to 0.52‰),indicating recycled carbonates have been added into their mantle source,which increased the mantle flow velocity.Combined with slab roll-back in the Late Mesozoic,it created the essential conditions for mantle flow to promote the formation of the eastern Asian BMW.展开更多
BACKGROUND Gastroesophageal junction(GEJ)or gastrointestinal stromal tumor(GIST)are located in unfavorable parts of the stomach,due to the anatomical complexity of these regions,protecting the cardia while ensuring R0...BACKGROUND Gastroesophageal junction(GEJ)or gastrointestinal stromal tumor(GIST)are located in unfavorable parts of the stomach,due to the anatomical complexity of these regions,protecting the cardia while ensuring R0 resection is a major challenge for surgeons.CASE SUMMARY Two cases of GEJ stromal tumors were reported.Abdominal computed tomography scans revealed that both tumors were located at the GEJ,close to the posterior wall,with one tumor measuring greater than 5 cm.Both patients successfully underwent robot-assisted laparoscopic wedge resection of the stomach.The surgeries achieved R0 resection while preserving the cardia sphincter and maximizing gastric tissue preservation.Postoperatively,no symptoms such as gastroesophageal reflux or cardia stenosis were observed.Case 1:Postoperative pathology:GIST.Immunohistochemical results:Tumor cells were positive for CD34,CD117,and DOG1,and negative for SMA,desmin,S-100,and SDHB(normal expression).The Ki-67 proliferation index was approximately 5%.Case 2:Postoperative pathology:GIST.Immunohistochemical results:Tumor cells were positive for CD117(++),CD34(++),DOG1(+++),and focal positivity for SMA.Negative for desmin,S-100(few cells positive),and SDHB(preserved expression).The Ki-67 proliferation index was approximately 10%.CONCLUSION The gastric tube-guided robotic-assisted laparoscopic resection is a safe and effective method for tumor resection while preserving the cardia,and it is worth further promotion in clinical practice.展开更多
Passive-roof duplexes accommodate shortening at the mountain front of many fold-and-thrust belts worldwide.These structures typically manifest at the surface by hinterland-verging backthrusts that decouple thin-skinne...Passive-roof duplexes accommodate shortening at the mountain front of many fold-and-thrust belts worldwide.These structures typically manifest at the surface by hinterland-verging backthrusts that decouple thin-skinned thrust sheets from underlying foreland-verging duplexes.Although the main fac-tors controlling the development of passive-roof duplexes have mostly been identified,some of their intrinsic characteristics are still poorly defined.These relate to their spatio-temporal relationships to thrust faults located further inland in orogens,and their ability to transport younger rocks over older ones.This study explores these issues in the Casentino-Romagna axial sector of the Northern Apennines,which expose regional forethrusts and backthrusts.Detailed field mapping and analysis of superposed tectonic structures were integrated with apatite fission-track dating for constraining the tim-ing of rock exhumation and correlated tectonic events.Collectively,the results have allowed us to inter-pret the evolution of the study area in terms of two main deformation stages.Specifically,a first,long phase(D_(1))progressed from NE-directed,in-sequence thrusting(∼18 to∼10-9 Ma)to late out-of-sequence thrusting(∼8-5 Ma).A successive deformation phase,that we refer to as D_(2)(∼4-2 Ma),con-sisted of backthrusts and associated folds that were ubiquitous and systematically overprinted onto the foreland-verging D_(1)structures.Such retrovergent structures identify a late deformation phase dom-inated by the development of passive-roof duplexes that propagated hinterlandward into the orogen up to beyond the primary watershed ridge.Orogen-scale processes controlled the evolution of forelandward D_(1)-phase thrusts,although late erosion could have played a major role by bringing the Apennine thrust wedge toward an undercritical state.The latter conditions could have contributed to keeping the out-of-sequence thrusts active,and eventually promoted the development of the D_(2)passive-roof duplexes.展开更多
The present study describes a river channel management method for restoring riverine environments degraded by sand mining in rivers.Specifically,three conditions that must be met for a restored river channel in the lo...The present study describes a river channel management method for restoring riverine environments degraded by sand mining in rivers.Specifically,three conditions that must be met for a restored river channel in the lower reach of the Kelani River in Sri Lanka were proposed:(1)flood discharge capacity of the channel for a given flood,(2)prevention of saltwater intrusion,and(3)creation of a diverse physical environment.The allowable mining volume satisfies the three conditions,while continuing to mine sand was discussed based on the sediment budget calculations in the target river reach.In this case,the amount of sediment stored in the target reach and its variation are determined by the amount of sediment supplied to the target reach,the amount of sediment discharged from the target reach to the sea,and the amount of sediment excavated.This means that the dynamic equilibrium channel of the target reach is determined by the amount of sediment supplied and the amount of sediment excavated.The amount of sand mined when the dynamic equilibrium channel meets the three conditions of the restored channel is a candidate for the allowable amount of sand mined.One of these,the most desirable one,is set as the allowable mining volume.As described above,we proposed a method to develop a restoring reach taking the sediment budget and associated hydraulic and hydro morphological conditions in the target reach into consideration.展开更多
Geomagnetic substorms release plasma and energy from the magnetotail to the inner magnetosphere and high latitude ionosphere.In this study,we investigate substorms of different time duration,observed during the years ...Geomagnetic substorms release plasma and energy from the magnetotail to the inner magnetosphere and high latitude ionosphere.In this study,we investigate substorms of different time duration,observed during the years 1982 to 2012.We measure substorm duration by a method based on the SME index.Our results demonstrate that longer-duration substorms occur more frequently during solar maximum years,and more frequently between the months of May and July,likely due to the higher polar ionospheric conductivity and more sunward geomagnetic pole directions during summer in the northern hemisphere.Additionally,longer substorms occur more frequently under stronger,longer-lasting southward IMF,and are accompanied by slower solar winds,suggesting that extended magnetic reconnection is required to drive longer substorms.Substorm durations are not significantly related to the minimum SML index,but longer substorms usually have higher SMU and continuously rising PC indices.The SME indices of long-duration substorms show a bimodal MLT distribution located near midnight and dusk after substorm onset,with the peak originally at midnight moving eastward to the morning side during the late recovery phase.Longer duration substorms have a stronger effect on the overall ring current at all MLT sectors except dawnside.Our results provide new insights into the development process and influencing factors of substorms,from the expansion phase to the recovery phase.展开更多
Island-arc magmatism is a crucial process in the Earth’s crustal growth.However,how the island-arc magma production rate(MPR)changes and the key influencing factors remains unclear.This study employs numerical models...Island-arc magmatism is a crucial process in the Earth’s crustal growth.However,how the island-arc magma production rate(MPR)changes and the key influencing factors remains unclear.This study employs numerical models to simulate island-arc growth,incorporating slab dehydration,mantle hydration and melting,and melt extraction.In addition,the impacts of convergence rate and slab dip angle on island-arc magma production were studied.Results suggest that,(1)MPR increases with higher convergence rates;high convergence rates enhance slab water transport efficiency and mantle wedge convection,thereby promoting water fraction and temperature in potential molten regions;(2)MPR initially rises and then falls as the slab dip angle varies from 30°to 45°,and to 60°.This variation is closely tied to water content in the wedge rather than mantle temperature.However,a higher slab dip promotes dehydration towards the potential-melting mantle wedge,which causes water to ascend to shallow areas and reduces the area of the potential molten region.Ultimately,a dip angle of 45°is optimal for retaining the most suitable water fraction and mantle wedge area,thereby maintaining the largest MPR;(3)convergence rate variation has a much larger influence on magma production rate than dip angle variation.When the convergence rate varies from 2 to 10 cm/a,the largest time-averaged MPR is 64.0 times the smallest one,whereas when the slab dip varies from 30°to 60°,the largest time-averaged MPR is only 3.5 times the smallest one.These findings align with numerous instances observed in modern-day subduction zones.展开更多
The goal of this research is to develop mine-scale discrete fracture network(DFN)models in which the influence of the spatial heterogeneity of fracture distributions may be investigated on the rock wedge stability of ...The goal of this research is to develop mine-scale discrete fracture network(DFN)models in which the influence of the spatial heterogeneity of fracture distributions may be investigated on the rock wedge stability of an open pit slope.For this purpose,spatially conditioned DFN models were developed for the pit walls at Tasiast mine using comprehensive structural data from the mine.Using Sequential Gaussian Simulation(SGS),volumetric fracture intensities(P32)were modeled across the entire mine site in the form of 3D block models.The simulated P32 block models were used as the input constraints for conditional DFN fracture generation,where the DFN grid dimension is the same as the SGS 3D blocks.The spatially constrained DFN models were further calibrated using aerial fracture intensities(P21)data from the pit walls,obtained by a survey of the pit walls using an unmanned aerial vehicle(UAV)and measured traces of joints from 3D point cloud data.The final DFN model is expected to honor the fracture intensities gathered through different means with optimal model accuracy.Finally,bench-scale and interramp scale rock wedge slope stability analyses were conducted using the calibrated conditional DFN models.This work proves the significance of conditioned DFN models in rock wedge stability analysis.Such models provide detailed information regarding rock wedge stability so that site monitoring and prevention plans can be conducted with higher efficiency.展开更多
The phenomenon of shock/shock interaction(SSI)is widely observed in high-speed flow,and the double wedge SSI represents one of the typical problems encountered.The control effect of single-pulse plasma synthetic jet(P...The phenomenon of shock/shock interaction(SSI)is widely observed in high-speed flow,and the double wedge SSI represents one of the typical problems encountered.The control effect of single-pulse plasma synthetic jet(PSJ)on double wedge type-Ⅵand type-ⅤSSI was investigated experimentally and numerically,and the influence of discharge energy was also explored.The findings indicate that the interaction between PSJ and the high-speed freestream results in the formation of a plasma layer and a jet shock,which collectively governs the control of SSI.The control mechanism of single-pulse PSJ on SSI lies in its capacity to attenuate both shock and SSI.For type-ⅥSSI,the original second-wedge oblique shock is eliminated under the control of PSJ,resulting in a new type-ⅥSSI formed by the jet shock and the first-wedge oblique shock.For type-ⅤSSI,the presence of PSJ effectively mitigates the intensity of Mach stem,supersonic jet,and reflected shocks,thereby facilitating its transition into type-ⅥSSI.The numerical results indicate that the peak pressure can be reduced by approximately 32.26%at maximum.Furthermore,the development of PSJ also extends in the Z direction.The pressure decreases in the area affected by both PSJ and jet shock due to the attenuation of the SSI zone.With increasing discharge energy,the control effect of PSJ on SSI is gradually enhanced.展开更多
304 stainless steel(SS)/Q235 carbon steel(CS)bimetallic composite shafts were prepared by the cross wedge rolling(CWR).The bonding interface welding mechanism was investigated through CWR rolling experiments and finit...304 stainless steel(SS)/Q235 carbon steel(CS)bimetallic composite shafts were prepared by the cross wedge rolling(CWR).The bonding interface welding mechanism was investigated through CWR rolling experiments and finite element simulation,as well as element diffusion,microstructure analysis,and mechanical property tests.According to simulation studies,the bonding interface is primarily subjected to three-directional compressive stresses at the tool-workpiece contact zone.As compression ratio increases from 0.25 to 0.35,the interface of the stress penetration area increases,while the diameter and wall thickness of CS/SS bimetallic shaft decrease,and hence,thickness-to-diameter ratio remains unchanged,which is conducive to the coordinated deformation of inner and outer metals and the interface of welded joints.The microstructure analysis of the interface shows that there are no obvious defects and cracks in the attachment,and that the microstructure on CS side is dominated by ferrite and martensite phases.Caused by the decarburization effect,Q235 steel microstructure features coarse ferrite,accompanied by a carburized layer with a thickness of about 20μm on SS side near the interface where grains are refined.As radial compression ratio increases,the diffusion distance of Cr,Ni,and other elements increases,the average thickness of the decarburized layer decreases,the interfacial bonding strength increases from 450 to 490 MPa,and metallurgical bonding at the interface is thus improved.The study demonstrates that it is feasible to use 304 SS and Q235 CS for cross wedge rolling composite shafts.展开更多
The boundary between cratonic and orogenic lithospheres is a significant seismogenic zones marked by intense lithospheric deformation.The Sichuan Craton(SCC),as a key tectonic block bordering eastern Tibetan Plateau,r...The boundary between cratonic and orogenic lithospheres is a significant seismogenic zones marked by intense lithospheric deformation.The Sichuan Craton(SCC),as a key tectonic block bordering eastern Tibetan Plateau,resists the eastward escape of plateau's crustal materials,resulting in the uplift of the Songpan-Ganzi Block(SGB)and crustal deformation of the Longmenshan tectonic belt(LMTB).To elucidate the compressional structures and deformational modes of the LMTB and SCC,it is essential to accurately determine the location and geometry of the SCC'western boundary.To investigate this issue,the lithospheric properties of the obducted SGB,underthrusting SCC,and LMTB were analyzed using various geophysical data,including seismic reflection profiles,magnetotellurics,aeromagnetics,gravity,and seismic tomography.The SGB crust is characterized by low magnetism,seismic velocity,resistivity and Bouguer gravity,whereas the SCC crust exhibits non-uniform high magnetism,seismic velocity,resistivity and Bouguer gravity.The LMTB,as the boundary between the SGB and SCC,exhibits geophysical characteristics similar to those of the SCC in the southern and central segments.The integration of these geophysical observations indicate that the SCC's western boundary is situated west of the Wenchuan-Maoxian fault zone in the southern and central segments,exhibiting distinct westward wedging and underthrusting.However,this boundary aligns with the Yingxiu-Beichuan fault in the northern segment,without significant underthrusting.The irregular geometry of the SCC's western boundary further elucidates the variation in structural deformation along the LMTB.By comparing crustal thickness and lithospheric strength between the SGB and SCC,this study posits that the differing crustal strength between tectonic blocks may control the irregular geometry of the SCC's western boundary.展开更多
The Makran accretionary wedge has the smallest subduction angle among any accretionary prism in the world. The factors controlling the spacing and morphological development of its deep thrust faults, as well as the fo...The Makran accretionary wedge has the smallest subduction angle among any accretionary prism in the world. The factors controlling the spacing and morphological development of its deep thrust faults, as well as the formation mechanism of shallow normal faults, remain unclear. Meanwhile, the factors affecting the continuity of plane faults must be comprehensively discussed. Clarifying the development characteristics and deformation mechanisms of the Makran accretionary wedge is crucial to effectively guide the exploration of gas hydrate deposits in the area. This study aims to interpret seismic data to identify typical structures in the Makran accretionary wedge, including deep imbricate thrust faults, shallow and small normal faults, wedge-shaped piggyback basins, mud diapirs with fuzzy and disorderly characteristics of reflection, décollements with a northward tilt of 1° – 2°, and large seamounts. Physical simulation-based experiments are performed to comprehensively analyze the results of the plane, section, and slices of the wedge. Results reveal that the distances between and shapes of thrust faults in the deep parts of the Makran accretionary wedge are controlled by the bottom décollement. The uplift of the thrust fault-related folds and the upwelling of the mud diapirs primarily contribute to the formation of small normal faults in the shallow part of the area. The mud diapirs originate from plastic material at the bottom, while those that have developed in the area near the trench are larger. Seamounts and mud diapirs break the continuity of fault plane distribution.展开更多
On 12th August 2015,a massive rapid long run-out rock landslide occurred in the Shanyang Vanadium Mine in Shaanxi Province,China,which claimed the lives of 65 miners.No heavy rainfalls,earthquakes,and mining blasts we...On 12th August 2015,a massive rapid long run-out rock landslide occurred in the Shanyang Vanadium Mine in Shaanxi Province,China,which claimed the lives of 65 miners.No heavy rainfalls,earthquakes,and mining blasts were recorded before the incident.Therefore,the failure mechanism and the cause of the long run-out movement are always in arguments.In this paper,we conducted a detailed field investigation,laboratory tests,block theory analysis,and numerical simulation to investigate the failure and long run-out mechanisms of the landslide.The field investigation results show that the source material of the rock landslide is a huge dolomite wedge block bedding on siliceous shale layers.Uniaxial compression tests indicate that the uniaxial compression strength of the intact dolomite is 130-140MPa and the dolomite shows a brittle failure mode.Due to the progressive downward erosion of the gully,the dolomite rock bridge at the slope toe became thinner.As the compression stress in the dolomite bridge increased to surpass its strength,the brittle failure of the bridge occurred.Then huge potential energy was released following the disintegration of the landslide,which led to the high acceleration of this rock landslide.The 3D discrete element simulation results suggest that the low intergranular friction contributes to the long run-out movement of this rock landslide.展开更多
To overcome the inaccuracy problem of the traditional wedge evaluation of steel plates and strips caused by the ran-domness of the thicknesses of two local points and improve the reliability of the wedge index,the dou...To overcome the inaccuracy problem of the traditional wedge evaluation of steel plates and strips caused by the ran-domness of the thicknesses of two local points and improve the reliability of the wedge index,the double-centroid method for the wedge evaluation was proposed,and a model based on the centroid theory was established.Meanwhile,an integral model for the discrete thickness values of the cross-section profiles was derived.The discussion focused on the distinct characteristics of the two-point method,asymmetric method,and double-centroid method in evaluating the asymmetric distribution of cross-sections.The three methods were employed to evaluate the wedge values of both the theoretical and measured cross-sections of steel plates and strips,and the accuracies of three wedge evaluation models were analyzed and discussed.The results showed that the double-centroid method objectively reflects the degree and variation characteristics of the wedge values of the cross-sections of steel plates and strips,and this method is feasible,reliable,and outstanding.展开更多
Interest in soundless chemical demolition agents(SCDAs),also known as expansive cements,as potentially viable alternatives to explosives for rock fragmentation,has been growing in recent years.Consequently,there is an...Interest in soundless chemical demolition agents(SCDAs),also known as expansive cements,as potentially viable alternatives to explosives for rock fragmentation,has been growing in recent years.Consequently,there is an increasing amount of literature on the use of SCDA for the breakage of rock blocks and boulders.Limited research has been conducted so far on the breakage of excavation fronts,such as tunnel or drift faces,using SCDA.This is due to the perception that the planar compressive in-situ stresses in the face would inhibit the creation and propagation of fracturing due to expansive pressure.This study proposes a novel V-cut method for demolishing rock panels under biaxial stress using SCDA.This method was examined through large-scale tests and numerical modelling.The rock panels were subjected to high biaxial confinements of 26 MPa and 40 MPa.Such a level of confinement corresponds to an in-situ stress state 1000 m below the surface in the Canadian shield.The V-cut drillhole pattern employs two sets of three SCDA holes angled at 45from the face of a Stanstead granite panel.The drillhole arrangement aims to create a V-shaped wedge in the plane of major principal stress.When angled drillholes are subjected to expansive pressure,they tend to cast out of the panel face,causing fragmentation.Two panels of 1 m×1 m×0.25 m were successfully demolished using the proposed method.The three-dimensional fast Lagrangian analysis code FLAC3D modelling was used to reconstruct the panel failure mechanism owing to the V-cut.This study demonstrates the feasibility of fragmenting an excavation front,such as a rock excavation face,with SCDA using a V-cut drill hole pattern while subjected to high biaxial confinement.展开更多
The lamellar hydrates of CAC were designed with the introduction of nano CaCO_(3)or Mg-Al hydrotalcite(M-A-H),and the effects on the green strength,pore structures,and high-temperature fracture behavior of alumina-spi...The lamellar hydrates of CAC were designed with the introduction of nano CaCO_(3)or Mg-Al hydrotalcite(M-A-H),and the effects on the green strength,pore structures,and high-temperature fracture behavior of alumina-spinel castables were investigated.The results show that nano CaCO_(3)or M-A-H stimulates rapidly the hydration of CAC and the formation of lamellar C_(4)AcH_(11)or coexistence of C_(2)AH_(8)and C_(4)AcH_(11)at 25℃.The formation of lamellar hydrates can contribute to a more complicated pore structure,especially in the range of 400-2000 nm.Meanwhile,the incorporation of well-distributed CaO or MgO sources from nano CaCO_(3)or M-A-H also regulates the distribution of CA_(6)and spinel(pre-formed and in-situ).Consequently,the optimized microstructure and complicated pore structure can induce the deflection and bridging of cracks,thus facilitating the consumption of fracture energy and enhancing the resistance to thermal stress damage.展开更多
BACKGROUND Osteoporosis is the leading cause of vertebral fractures.Dual-energy X-ray absor-ptiometry(DXA)and radiographs are traditionally used to detect osteoporosis and vertebral fractures/deformities.Magnetic reso...BACKGROUND Osteoporosis is the leading cause of vertebral fractures.Dual-energy X-ray absor-ptiometry(DXA)and radiographs are traditionally used to detect osteoporosis and vertebral fractures/deformities.Magnetic resonance imaging(MRI)can be utilized to detect the relative severity of vertebral deformities using three-dimen-sional information not available in traditional DXA and lateral two-dimensional radiography imaging techniques.AIM To generate normative vertebral parameters in women using MRI and DXA scans,determine the correlations between MRI-calculated vertebral deformities and age,DXA T-scores,and DXA Z-scores,and compare MRI vertebral deformity values with radiography values previously published in the literature.METHODS This study is a retrospective vertebral morphometric analysis conducted at our institution.The patient sample included MR images from 1638 female patients who underwent both MR and DXA imaging between 2005 and 2014.Biconcavity,wedge,crush,anterior height(Ha)/posterior height(Hp),and middle height(Hm)/posterior height values were calculated from the MR images of the patient’s vertebrae.Associations between vertebral deformity values,patient age,and DXA T-scores were analyzed using Spearman correlation.The MRI-derived measure-ments were compared with radiograph-based calculations from population-based data compiled from multiple studies.RESULTS Age was positively correlated with lumbar Hm/Hp(P=0.04)and thoracic wedge(P=0.03)and biconcavity(P=0.001)and negatively correlated with thoracic Ha/Hp(P=0.002)and Hm/Hp(P=0.001)values.DXA T-scores correlated positively with lumbar Hm/Hp(P<0.0001)and negatively with lumbar wedge(P=0.046),biconcavity(P<0.0001),and Ha/Hp(P=0.046)values.Qualitative analysis revealed that Ha/Hp differed between MRI and radiography population-based data by no more than 0.3 and Hm/Hp by a maximum of 1.2.CONCLUSION Compared with traditional imaging techniques,MRI detects vertebral deformities with high accuracy and re-liability.It may be a sensitive,ionizing,radiation-free tool for use in clinical settings.展开更多
基金Supported by the National Natural Science Foundation of China (No. 10472081 and No. 10232020)
文摘Turbulent flow field of the free jet with circular nozzle and wedged nozzles is measured using hot wire anemometry with resolution higher than the smallest turbulence time scale. Wavelet analysis is employed to perform multi-scale decomposition of instantaneous turbulence fluctuating velocity signals, and the energy distribution of the turbulent multi-scale eddy structures over scales is studied using wavelet coefficients. Investigation of the multi-scale eddy structures of circular jet and various wedged jets reveals the transport of the energy of these wedged jets in the space from the axis to the side of the jet, as compared with the circular jet. Furthermore, not only the eddy structures at the wedge tines in the near field are crashed, but also the interactions such as eddy structure union and entrainment take place at different longitudinal and normal locations along with the development of the jets because of the existence of wedges.
文摘Aim: The purpose of this study was to make a comparison between measured and calculated physical wedge dose distributions using the superposition algorithm. Settings and Design: The accurate determination of absorbed dose is important radiotherapy because of the relatively steep sigmoidal dose response curves for both tumor control and normal-tissue damage. Materials and Methods: High-energy photons (6 and 10 MV) from Artiste Treatment System Linear Accelerator Machine, available at Alexandria Ayadi Al-Mostakbal Oncology Center, were used. Results and Discussion: The results showed that the difference between measured and calculated wedged isodose curves depends on field size, beam energy, and the angle of the used wedge. Conclusion: The results showed that the presence of a wedge alters the primary and scattered components generated by a linear accelerator and causes beam hardening in 6 and 10 MV. The beam hardening increased as the wedge angle increased.
基金Supported by Capital Medical University Affiliated Beijing Shijitan Hospital Talent Development Program during the 14th Five-Year Plan,No.2023 LJRCLFQ.
文摘BACKGROUND Wedged hepatic venous pressure(WHVP)is a crucial variable for accurately assessing the hepatic venous pressure gradient(HVPG)and is vital for the diagnosis and prognostic evaluation of patients with portal hypertension(PH).AIM To investigate the anatomical characteristics of balloon-occluded hepatic venous angiography in patients with PH and analyze the relationship between the WHVP and portal venous pressure(PVP).METHODS This retrospective study included 877 patients with PH who met the inclusion criteria from January 2020 to June 2024.Routine and innovative hepatic venous angiography was performed during transjugular intrahepatic portosystemic shunt procedures to measure hepatic venous and PVPs.All patients'angiographic images were collected for analysis.The associations between WHVP and PVP in each group were analyzed via linear regression analysis,and a predictive model was established.RESULTS The 877 patients had a mean age of 52.6±13.0 years,with 582 males and 295 females.Patients were categorized into four groups on the basis of their anatomical structure.All groups showed strong correlations between WHVP and PVP.The regression coefficient between the WHVP and PVP in the hepatic right vein-portal venous angiography group was 0.884(P<0.05);in the hepatic right vein-accessory hepatic venous angiography group,it was 0.721(P<0.05);in the hepatic right vein-middle hepatic venous angiography group,it was 0.344(P<0.05);and in the hepatic right vein-nonangiography group,it was 0.293(P<0.05).CONCLUSION The presence and anatomical classification of hepatic venous collaterals are key factors influencing the relationship between WHVP with and PVP.Based on the different anatomical classifications of hepatic veins,WHVP can be used to estimate PVP,improving the accuracy of PVP prediction.
基金financially supported by the National Key R&D Program of China(No.2022YFF0801002)the National Natural Science Foundation of China(No.42372065)the Natural Science Foundation of Jilin Province(No.20220101178JC)。
文摘The Paleo-Pacific Plate stagnated in the mantle transition zone beneath northeast Asia during the Late Mesozoic,resulting in the eastern Asian big mantle wedge(BMW).However,its formation mechanism remains unclear.Here,we analyzed elemental and isotopic compositions of 126-60 Ma intraplate basaltic rocks to map the mantle flow pattern and investigate the implications for the formation of the BMW.These rocks exhibit eastward an increase in Ba/Nb,Ba/La,^(87)Sr/^(86)Sr,and^(208)Pb/^(204)Pb ratios,while a decrease in Nb/Yb,Zr/Yb,Ta/Yb,and Nb/Nb*ratios,indicating mixing between the fertile mantle and the depleted mantle modified by slab material,implying the occurrence of trench-perpendicular mantle flow.The coeval mantle flow and formation of the BMW,the similar directions of mantle flow and Paleo-Pacific Plate subduction,and migration of basin depocenters indicate trench-perpendicular mantle flow was a key factor in the formation of the BMW.Moreover,these basaltic rocks have elevatedδ^(66)Zn values(0.22‰to 0.52‰),indicating recycled carbonates have been added into their mantle source,which increased the mantle flow velocity.Combined with slab roll-back in the Late Mesozoic,it created the essential conditions for mantle flow to promote the formation of the eastern Asian BMW.
基金Supported by Jiangsu Provincial Administration of Traditional Chinese Medicine,No.MS2023017 and No.SLJ0311the Jiangsu Provincial Health Commission,No.ZDXK202251.
文摘BACKGROUND Gastroesophageal junction(GEJ)or gastrointestinal stromal tumor(GIST)are located in unfavorable parts of the stomach,due to the anatomical complexity of these regions,protecting the cardia while ensuring R0 resection is a major challenge for surgeons.CASE SUMMARY Two cases of GEJ stromal tumors were reported.Abdominal computed tomography scans revealed that both tumors were located at the GEJ,close to the posterior wall,with one tumor measuring greater than 5 cm.Both patients successfully underwent robot-assisted laparoscopic wedge resection of the stomach.The surgeries achieved R0 resection while preserving the cardia sphincter and maximizing gastric tissue preservation.Postoperatively,no symptoms such as gastroesophageal reflux or cardia stenosis were observed.Case 1:Postoperative pathology:GIST.Immunohistochemical results:Tumor cells were positive for CD34,CD117,and DOG1,and negative for SMA,desmin,S-100,and SDHB(normal expression).The Ki-67 proliferation index was approximately 5%.Case 2:Postoperative pathology:GIST.Immunohistochemical results:Tumor cells were positive for CD117(++),CD34(++),DOG1(+++),and focal positivity for SMA.Negative for desmin,S-100(few cells positive),and SDHB(preserved expression).The Ki-67 proliferation index was approximately 10%.CONCLUSION The gastric tube-guided robotic-assisted laparoscopic resection is a safe and effective method for tumor resection while preserving the cardia,and it is worth further promotion in clinical practice.
文摘Passive-roof duplexes accommodate shortening at the mountain front of many fold-and-thrust belts worldwide.These structures typically manifest at the surface by hinterland-verging backthrusts that decouple thin-skinned thrust sheets from underlying foreland-verging duplexes.Although the main fac-tors controlling the development of passive-roof duplexes have mostly been identified,some of their intrinsic characteristics are still poorly defined.These relate to their spatio-temporal relationships to thrust faults located further inland in orogens,and their ability to transport younger rocks over older ones.This study explores these issues in the Casentino-Romagna axial sector of the Northern Apennines,which expose regional forethrusts and backthrusts.Detailed field mapping and analysis of superposed tectonic structures were integrated with apatite fission-track dating for constraining the tim-ing of rock exhumation and correlated tectonic events.Collectively,the results have allowed us to inter-pret the evolution of the study area in terms of two main deformation stages.Specifically,a first,long phase(D_(1))progressed from NE-directed,in-sequence thrusting(∼18 to∼10-9 Ma)to late out-of-sequence thrusting(∼8-5 Ma).A successive deformation phase,that we refer to as D_(2)(∼4-2 Ma),con-sisted of backthrusts and associated folds that were ubiquitous and systematically overprinted onto the foreland-verging D_(1)structures.Such retrovergent structures identify a late deformation phase dom-inated by the development of passive-roof duplexes that propagated hinterlandward into the orogen up to beyond the primary watershed ridge.Orogen-scale processes controlled the evolution of forelandward D_(1)-phase thrusts,although late erosion could have played a major role by bringing the Apennine thrust wedge toward an undercritical state.The latter conditions could have contributed to keeping the out-of-sequence thrusts active,and eventually promoted the development of the D_(2)passive-roof duplexes.
基金Tokyo Metropolitan Government,Grant/Award Number:Advanced Research Grant Number(R4-2)。
文摘The present study describes a river channel management method for restoring riverine environments degraded by sand mining in rivers.Specifically,three conditions that must be met for a restored river channel in the lower reach of the Kelani River in Sri Lanka were proposed:(1)flood discharge capacity of the channel for a given flood,(2)prevention of saltwater intrusion,and(3)creation of a diverse physical environment.The allowable mining volume satisfies the three conditions,while continuing to mine sand was discussed based on the sediment budget calculations in the target river reach.In this case,the amount of sediment stored in the target reach and its variation are determined by the amount of sediment supplied to the target reach,the amount of sediment discharged from the target reach to the sea,and the amount of sediment excavated.This means that the dynamic equilibrium channel of the target reach is determined by the amount of sediment supplied and the amount of sediment excavated.The amount of sand mined when the dynamic equilibrium channel meets the three conditions of the restored channel is a candidate for the allowable amount of sand mined.One of these,the most desirable one,is set as the allowable mining volume.As described above,we proposed a method to develop a restoring reach taking the sediment budget and associated hydraulic and hydro morphological conditions in the target reach into consideration.
基金supported by NSFC research Grant 42274200National Key R&D Program of China 2023YFC2808900the International Space Science Institute(ISSI)in Bern,through ISSI International Team project#24-628-Precipitation of Energetic Particles from Magnetosphere and Their Effects on the Atmosphere.
文摘Geomagnetic substorms release plasma and energy from the magnetotail to the inner magnetosphere and high latitude ionosphere.In this study,we investigate substorms of different time duration,observed during the years 1982 to 2012.We measure substorm duration by a method based on the SME index.Our results demonstrate that longer-duration substorms occur more frequently during solar maximum years,and more frequently between the months of May and July,likely due to the higher polar ionospheric conductivity and more sunward geomagnetic pole directions during summer in the northern hemisphere.Additionally,longer substorms occur more frequently under stronger,longer-lasting southward IMF,and are accompanied by slower solar winds,suggesting that extended magnetic reconnection is required to drive longer substorms.Substorm durations are not significantly related to the minimum SML index,but longer substorms usually have higher SMU and continuously rising PC indices.The SME indices of long-duration substorms show a bimodal MLT distribution located near midnight and dusk after substorm onset,with the peak originally at midnight moving eastward to the morning side during the late recovery phase.Longer duration substorms have a stronger effect on the overall ring current at all MLT sectors except dawnside.Our results provide new insights into the development process and influencing factors of substorms,from the expansion phase to the recovery phase.
基金Supported by the National Natural Science Foundation of China(Nos.42176068,42476063,92058213,42376081,42121005)。
文摘Island-arc magmatism is a crucial process in the Earth’s crustal growth.However,how the island-arc magma production rate(MPR)changes and the key influencing factors remains unclear.This study employs numerical models to simulate island-arc growth,incorporating slab dehydration,mantle hydration and melting,and melt extraction.In addition,the impacts of convergence rate and slab dip angle on island-arc magma production were studied.Results suggest that,(1)MPR increases with higher convergence rates;high convergence rates enhance slab water transport efficiency and mantle wedge convection,thereby promoting water fraction and temperature in potential molten regions;(2)MPR initially rises and then falls as the slab dip angle varies from 30°to 45°,and to 60°.This variation is closely tied to water content in the wedge rather than mantle temperature.However,a higher slab dip promotes dehydration towards the potential-melting mantle wedge,which causes water to ascend to shallow areas and reduces the area of the potential molten region.Ultimately,a dip angle of 45°is optimal for retaining the most suitable water fraction and mantle wedge area,thereby maintaining the largest MPR;(3)convergence rate variation has a much larger influence on magma production rate than dip angle variation.When the convergence rate varies from 2 to 10 cm/a,the largest time-averaged MPR is 64.0 times the smallest one,whereas when the slab dip varies from 30°to 60°,the largest time-averaged MPR is only 3.5 times the smallest one.These findings align with numerous instances observed in modern-day subduction zones.
基金Kinross Gold and MITACS for their financial support(Grant No.FR42880).
文摘The goal of this research is to develop mine-scale discrete fracture network(DFN)models in which the influence of the spatial heterogeneity of fracture distributions may be investigated on the rock wedge stability of an open pit slope.For this purpose,spatially conditioned DFN models were developed for the pit walls at Tasiast mine using comprehensive structural data from the mine.Using Sequential Gaussian Simulation(SGS),volumetric fracture intensities(P32)were modeled across the entire mine site in the form of 3D block models.The simulated P32 block models were used as the input constraints for conditional DFN fracture generation,where the DFN grid dimension is the same as the SGS 3D blocks.The spatially constrained DFN models were further calibrated using aerial fracture intensities(P21)data from the pit walls,obtained by a survey of the pit walls using an unmanned aerial vehicle(UAV)and measured traces of joints from 3D point cloud data.The final DFN model is expected to honor the fracture intensities gathered through different means with optimal model accuracy.Finally,bench-scale and interramp scale rock wedge slope stability analyses were conducted using the calibrated conditional DFN models.This work proves the significance of conditioned DFN models in rock wedge stability analysis.Such models provide detailed information regarding rock wedge stability so that site monitoring and prevention plans can be conducted with higher efficiency.
基金supported by the Independent Innovation Science Fund of National University of Defense Technology(No.24-ZZCX-BC-05)National Natural Science Foundation of China(Nos.92271110 and 12202488)+2 种基金the Major National Science and Technology Project(No.J2019-Ⅲ0010-0054)the National Postdoctoral Researcher Program of China(No.GZB20230985)the Natural Science Program of National University of Defense Technology(No.ZK22-30)。
文摘The phenomenon of shock/shock interaction(SSI)is widely observed in high-speed flow,and the double wedge SSI represents one of the typical problems encountered.The control effect of single-pulse plasma synthetic jet(PSJ)on double wedge type-Ⅵand type-ⅤSSI was investigated experimentally and numerically,and the influence of discharge energy was also explored.The findings indicate that the interaction between PSJ and the high-speed freestream results in the formation of a plasma layer and a jet shock,which collectively governs the control of SSI.The control mechanism of single-pulse PSJ on SSI lies in its capacity to attenuate both shock and SSI.For type-ⅥSSI,the original second-wedge oblique shock is eliminated under the control of PSJ,resulting in a new type-ⅥSSI formed by the jet shock and the first-wedge oblique shock.For type-ⅤSSI,the presence of PSJ effectively mitigates the intensity of Mach stem,supersonic jet,and reflected shocks,thereby facilitating its transition into type-ⅥSSI.The numerical results indicate that the peak pressure can be reduced by approximately 32.26%at maximum.Furthermore,the development of PSJ also extends in the Z direction.The pressure decreases in the area affected by both PSJ and jet shock due to the attenuation of the SSI zone.With increasing discharge energy,the control effect of PSJ on SSI is gradually enhanced.
基金supported by National Key Research and Development Program of China(No.2022YFE0123700)National Natural Science Foundation of China(Grant No.52275307)the Engineering Research Center of Part Rolling,Ministry of Education,China.
文摘304 stainless steel(SS)/Q235 carbon steel(CS)bimetallic composite shafts were prepared by the cross wedge rolling(CWR).The bonding interface welding mechanism was investigated through CWR rolling experiments and finite element simulation,as well as element diffusion,microstructure analysis,and mechanical property tests.According to simulation studies,the bonding interface is primarily subjected to three-directional compressive stresses at the tool-workpiece contact zone.As compression ratio increases from 0.25 to 0.35,the interface of the stress penetration area increases,while the diameter and wall thickness of CS/SS bimetallic shaft decrease,and hence,thickness-to-diameter ratio remains unchanged,which is conducive to the coordinated deformation of inner and outer metals and the interface of welded joints.The microstructure analysis of the interface shows that there are no obvious defects and cracks in the attachment,and that the microstructure on CS side is dominated by ferrite and martensite phases.Caused by the decarburization effect,Q235 steel microstructure features coarse ferrite,accompanied by a carburized layer with a thickness of about 20μm on SS side near the interface where grains are refined.As radial compression ratio increases,the diffusion distance of Cr,Ni,and other elements increases,the average thickness of the decarburized layer decreases,the interfacial bonding strength increases from 450 to 490 MPa,and metallurgical bonding at the interface is thus improved.The study demonstrates that it is feasible to use 304 SS and Q235 CS for cross wedge rolling composite shafts.
基金supported by the National Natural Science Foundation of China(Nos.U22B6002,42422402,41902202 and 42276222)the SINOPEC Key Laboratory of Geophysics(No.FW0399-0029)+2 种基金the Second Tibetan Plateau Scientific Expedition and Research(No.2019QZKK00708)the Development Fund of South China Sea Institute of Oceanology of the Chinese Academy of Sciences(No.SCSIO202207)the Special Fund of the Institute of Geophysics,China Earthquake Administration(No.DQJB22B23)。
文摘The boundary between cratonic and orogenic lithospheres is a significant seismogenic zones marked by intense lithospheric deformation.The Sichuan Craton(SCC),as a key tectonic block bordering eastern Tibetan Plateau,resists the eastward escape of plateau's crustal materials,resulting in the uplift of the Songpan-Ganzi Block(SGB)and crustal deformation of the Longmenshan tectonic belt(LMTB).To elucidate the compressional structures and deformational modes of the LMTB and SCC,it is essential to accurately determine the location and geometry of the SCC'western boundary.To investigate this issue,the lithospheric properties of the obducted SGB,underthrusting SCC,and LMTB were analyzed using various geophysical data,including seismic reflection profiles,magnetotellurics,aeromagnetics,gravity,and seismic tomography.The SGB crust is characterized by low magnetism,seismic velocity,resistivity and Bouguer gravity,whereas the SCC crust exhibits non-uniform high magnetism,seismic velocity,resistivity and Bouguer gravity.The LMTB,as the boundary between the SGB and SCC,exhibits geophysical characteristics similar to those of the SCC in the southern and central segments.The integration of these geophysical observations indicate that the SCC's western boundary is situated west of the Wenchuan-Maoxian fault zone in the southern and central segments,exhibiting distinct westward wedging and underthrusting.However,this boundary aligns with the Yingxiu-Beichuan fault in the northern segment,without significant underthrusting.The irregular geometry of the SCC's western boundary further elucidates the variation in structural deformation along the LMTB.By comparing crustal thickness and lithospheric strength between the SGB and SCC,this study posits that the differing crustal strength between tectonic blocks may control the irregular geometry of the SCC's western boundary.
基金funded by the National Natural Science Foundation of China(No.42076069).
文摘The Makran accretionary wedge has the smallest subduction angle among any accretionary prism in the world. The factors controlling the spacing and morphological development of its deep thrust faults, as well as the formation mechanism of shallow normal faults, remain unclear. Meanwhile, the factors affecting the continuity of plane faults must be comprehensively discussed. Clarifying the development characteristics and deformation mechanisms of the Makran accretionary wedge is crucial to effectively guide the exploration of gas hydrate deposits in the area. This study aims to interpret seismic data to identify typical structures in the Makran accretionary wedge, including deep imbricate thrust faults, shallow and small normal faults, wedge-shaped piggyback basins, mud diapirs with fuzzy and disorderly characteristics of reflection, décollements with a northward tilt of 1° – 2°, and large seamounts. Physical simulation-based experiments are performed to comprehensively analyze the results of the plane, section, and slices of the wedge. Results reveal that the distances between and shapes of thrust faults in the deep parts of the Makran accretionary wedge are controlled by the bottom décollement. The uplift of the thrust fault-related folds and the upwelling of the mud diapirs primarily contribute to the formation of small normal faults in the shallow part of the area. The mud diapirs originate from plastic material at the bottom, while those that have developed in the area near the trench are larger. Seamounts and mud diapirs break the continuity of fault plane distribution.
基金funded by the National Key R&D Program of China(2021YFE0111900)the China Postdoctoral Science Foundation(2023M730353)+1 种基金Major Program of National Natural Science Foundation of China(Grant No.42041006)Natural Science Basic Research Program of Shaanxi(Program No.2022JM-167).
文摘On 12th August 2015,a massive rapid long run-out rock landslide occurred in the Shanyang Vanadium Mine in Shaanxi Province,China,which claimed the lives of 65 miners.No heavy rainfalls,earthquakes,and mining blasts were recorded before the incident.Therefore,the failure mechanism and the cause of the long run-out movement are always in arguments.In this paper,we conducted a detailed field investigation,laboratory tests,block theory analysis,and numerical simulation to investigate the failure and long run-out mechanisms of the landslide.The field investigation results show that the source material of the rock landslide is a huge dolomite wedge block bedding on siliceous shale layers.Uniaxial compression tests indicate that the uniaxial compression strength of the intact dolomite is 130-140MPa and the dolomite shows a brittle failure mode.Due to the progressive downward erosion of the gully,the dolomite rock bridge at the slope toe became thinner.As the compression stress in the dolomite bridge increased to surpass its strength,the brittle failure of the bridge occurred.Then huge potential energy was released following the disintegration of the landslide,which led to the high acceleration of this rock landslide.The 3D discrete element simulation results suggest that the low intergranular friction contributes to the long run-out movement of this rock landslide.
基金supported by the National Natural Science Foundation of China (Grant No.52305405)the Natural Science Foundation Research Program of Shanxi Province (Grant No.202203021222121)+4 种基金the Major Project of Science and Technology of Shanxi Province (Grant No.20181102016)the Chinese Postdoctoral Science Foundation (Grant No.2021M702544)the Central Government Guides the Special Fund Projects of Local Scientific and Technological Development (YDZX20191400002149)the Open Project of Research Institute of Hai'an-Taiyuan University of Technology (Grant No.2023HA-TYUTKFYF008)the School Fund of Taiyuan University of Technology (Grant No.2022QN007).
文摘To overcome the inaccuracy problem of the traditional wedge evaluation of steel plates and strips caused by the ran-domness of the thicknesses of two local points and improve the reliability of the wedge index,the double-centroid method for the wedge evaluation was proposed,and a model based on the centroid theory was established.Meanwhile,an integral model for the discrete thickness values of the cross-section profiles was derived.The discussion focused on the distinct characteristics of the two-point method,asymmetric method,and double-centroid method in evaluating the asymmetric distribution of cross-sections.The three methods were employed to evaluate the wedge values of both the theoretical and measured cross-sections of steel plates and strips,and the accuracies of three wedge evaluation models were analyzed and discussed.The results showed that the double-centroid method objectively reflects the degree and variation characteristics of the wedge values of the cross-sections of steel plates and strips,and this method is feasible,reliable,and outstanding.
基金supported by a research grant from Natural Resources Canada,Clean Growth Program(Grant No.CGP-17-1003)and industry partner Newmont Corporation.
文摘Interest in soundless chemical demolition agents(SCDAs),also known as expansive cements,as potentially viable alternatives to explosives for rock fragmentation,has been growing in recent years.Consequently,there is an increasing amount of literature on the use of SCDA for the breakage of rock blocks and boulders.Limited research has been conducted so far on the breakage of excavation fronts,such as tunnel or drift faces,using SCDA.This is due to the perception that the planar compressive in-situ stresses in the face would inhibit the creation and propagation of fracturing due to expansive pressure.This study proposes a novel V-cut method for demolishing rock panels under biaxial stress using SCDA.This method was examined through large-scale tests and numerical modelling.The rock panels were subjected to high biaxial confinements of 26 MPa and 40 MPa.Such a level of confinement corresponds to an in-situ stress state 1000 m below the surface in the Canadian shield.The V-cut drillhole pattern employs two sets of three SCDA holes angled at 45from the face of a Stanstead granite panel.The drillhole arrangement aims to create a V-shaped wedge in the plane of major principal stress.When angled drillholes are subjected to expansive pressure,they tend to cast out of the panel face,causing fragmentation.Two panels of 1 m×1 m×0.25 m were successfully demolished using the proposed method.The three-dimensional fast Lagrangian analysis code FLAC3D modelling was used to reconstruct the panel failure mechanism owing to the V-cut.This study demonstrates the feasibility of fragmenting an excavation front,such as a rock excavation face,with SCDA using a V-cut drill hole pattern while subjected to high biaxial confinement.
基金supported financially by the Natural Science Foundation of Qinghai(2022-ZJ-928)the Special Project for Transformation of Scientific and Technological Achievements of Qinghai Province(2023-GX-102).
文摘The lamellar hydrates of CAC were designed with the introduction of nano CaCO_(3)or Mg-Al hydrotalcite(M-A-H),and the effects on the green strength,pore structures,and high-temperature fracture behavior of alumina-spinel castables were investigated.The results show that nano CaCO_(3)or M-A-H stimulates rapidly the hydration of CAC and the formation of lamellar C_(4)AcH_(11)or coexistence of C_(2)AH_(8)and C_(4)AcH_(11)at 25℃.The formation of lamellar hydrates can contribute to a more complicated pore structure,especially in the range of 400-2000 nm.Meanwhile,the incorporation of well-distributed CaO or MgO sources from nano CaCO_(3)or M-A-H also regulates the distribution of CA_(6)and spinel(pre-formed and in-situ).Consequently,the optimized microstructure and complicated pore structure can induce the deflection and bridging of cracks,thus facilitating the consumption of fracture energy and enhancing the resistance to thermal stress damage.
基金the Institutional Review Board at the University of Pennsylvania (Approval No.824040).
文摘BACKGROUND Osteoporosis is the leading cause of vertebral fractures.Dual-energy X-ray absor-ptiometry(DXA)and radiographs are traditionally used to detect osteoporosis and vertebral fractures/deformities.Magnetic resonance imaging(MRI)can be utilized to detect the relative severity of vertebral deformities using three-dimen-sional information not available in traditional DXA and lateral two-dimensional radiography imaging techniques.AIM To generate normative vertebral parameters in women using MRI and DXA scans,determine the correlations between MRI-calculated vertebral deformities and age,DXA T-scores,and DXA Z-scores,and compare MRI vertebral deformity values with radiography values previously published in the literature.METHODS This study is a retrospective vertebral morphometric analysis conducted at our institution.The patient sample included MR images from 1638 female patients who underwent both MR and DXA imaging between 2005 and 2014.Biconcavity,wedge,crush,anterior height(Ha)/posterior height(Hp),and middle height(Hm)/posterior height values were calculated from the MR images of the patient’s vertebrae.Associations between vertebral deformity values,patient age,and DXA T-scores were analyzed using Spearman correlation.The MRI-derived measure-ments were compared with radiograph-based calculations from population-based data compiled from multiple studies.RESULTS Age was positively correlated with lumbar Hm/Hp(P=0.04)and thoracic wedge(P=0.03)and biconcavity(P=0.001)and negatively correlated with thoracic Ha/Hp(P=0.002)and Hm/Hp(P=0.001)values.DXA T-scores correlated positively with lumbar Hm/Hp(P<0.0001)and negatively with lumbar wedge(P=0.046),biconcavity(P<0.0001),and Ha/Hp(P=0.046)values.Qualitative analysis revealed that Ha/Hp differed between MRI and radiography population-based data by no more than 0.3 and Hm/Hp by a maximum of 1.2.CONCLUSION Compared with traditional imaging techniques,MRI detects vertebral deformities with high accuracy and re-liability.It may be a sensitive,ionizing,radiation-free tool for use in clinical settings.
