Chemical doping is a critical factor in the development of new superconductors or optimizing the superconducting transition temperature(T_(c))of the parent superconducting materials.Here,a new simple urea approach is ...Chemical doping is a critical factor in the development of new superconductors or optimizing the superconducting transition temperature(T_(c))of the parent superconducting materials.Here,a new simple urea approach is developed to synthesize the N-dopedα-Mo_(2)C.Benefiting from the simple urea method,a broad superconducting dome is found in the Mo_(2)C_(1−x)N_(x)(0≤x≤0.49)compositions.X-ray diffraction results show that the structure of𝛼α-Mo_(2)C remains unchanged and there is a variation of lattice parameters with nitrogen doping.Resistivity,magnetic susceptibility,and heat capacity measurement results confirm that T_(c)was strongly increased from 2.68K(x=0)to 7.05K(x=0.49).First-principles calculations and our analysis indicate that increasing nitrogen doping leads to a rise in the density of states at the Fermi level and doping-induced phonon softening,which enhances electron–phonon coupling.This results in an increase in𝑇T_(c)and a sharp rise in the upper critical field.Our findings provide a promising strategy for fabricating transition metal carbonitrides and provide a material platform for further study of the superconductivity of transition metal carbides.展开更多
Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and operations.Previous studies have identified that disc...Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and operations.Previous studies have identified that discontinuous,layered roof materials have some self-supporting capacity.This research is a preliminary step towards understanding these mechanics in coal-measure rocks.Although others have considered broad conceptual models and simplified analogs for mine roof behavior,this study presents a unique numerical model that more completely represents in-situ roof conditions.The discrete element method(DEM)is utilized to conduct a parametric analysis considering a range of in-situ stress ratios,material properties,and joint networks to determine the parameters controlling the stability of single-entries modeled in two-dimensions.Model results are compared to empirical observations of roof-support effectiveness(ARBS)in the context of the coal mine roof rating(CMRR)system.Results such as immediate roof displacement,overall stability,and statistical relationships between model parameters and outcomes are presented herein.Potential practical applications of this line of research include:(1)roof-support optimization for a range of coal-measure rocks,(2)establishment of a relationship between roof stability and pillar stress,and(3)determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.展开更多
Optical analyzer technique are used to measure the sound speed as a function of pressure for shocked multiphase alloy 93 W containing 93%W, with 4.2%Ni-2.45%Fe-0.35%Co alloy as binder, all in wt.%. Below 250 GPa, the ...Optical analyzer technique are used to measure the sound speed as a function of pressure for shocked multiphase alloy 93 W containing 93%W, with 4.2%Ni-2.45%Fe-0.35%Co alloy as binder, all in wt.%. Below 250 GPa, the speed increases with pressure, then a bulk“softening” process occurs at 250 to 340 GPa, afterwards the speed again rises with pressure and coincides with the calculated bulk sound speed, showing a fluid-like behavior for this alloy. Lindemann melting law calculations were made for both the binder and the tungsten. The results showed that 250 GPa corresponds approximately to the pressure for the binder beginning to melt, and 340GPa corresponds to that for tungsten. Therefore, we believe that the shock-induced “softening” mechanism for this kind of multiphase alloys can be attributed to the binder melting.展开更多
Sulfur and lanthanum hydrides under compression display superconducting states with high observed critical temperatures.It has been recently demonstrated that carbonaceous sulfur hydride displays room temperature supe...Sulfur and lanthanum hydrides under compression display superconducting states with high observed critical temperatures.It has been recently demonstrated that carbonaceous sulfur hydride displays room temperature superconductivity.However,this phenomenon has been observed only at very high pressure.Here,we theoretically search for superconductors with very high critical temperatures,but at much lower pressures.We describe two of such sodalite-type clathrate hydrides,YbH6 and LuH6.These hydrides are metastable and are predicted to superconduct with T_(c)~145 K at 70 GPa and T_(c)~273 K at 100 GPa,respectively.This striking result is a consequence of the strong interrelationship between the f states present at the Fermi level,structural stability,and the final T_(c) value.For example,TmH6,with unfilled 4f orbitals,is stable at 50 GPa,but has a relatively low value of T_(c) of 25 K.The YbH6 and LuH6 compounds,with their filled f-shells,exhibit prominent phonon"softening",which leads to a strong electron-phonon coupling,and as a result,an increase in T_(c).展开更多
In some of the coalfields in India, coal seams are only developed but no extraction of pillars is possible due to the presence of surface or sub-surface structures and also non-availability of stowing materials which ...In some of the coalfields in India, coal seams are only developed but no extraction of pillars is possible due to the presence of surface or sub-surface structures and also non-availability of stowing materials which leads to huge amounts of coal being locked-up underground. Spontaneous heating and fire, accumulation of poisonous gases, severe stability issues leading to unsafe workings and environmental hazards are the major problems associated with the developed coal pillars. So, there is a pressing need for a technology for the mining industry to extract the huge amount of coal locked-up under different constraints. In this study, the locked-up coal is proposed to be extracted by artificially strengthening the rib pillars. The detailed comparative study is carried out to know the increase of extraction percentage of locked-up coal by strengthening the rib pillars with FRP. Extraction methodology is designed and studied through numerical modelling for its stability analysis to evaluate its suitability of application in underground.展开更多
According to the tensile failure of rock bolt in weakly cemented soft rock, this paper presents a new segmented anchoring style in order to weaken the cumulative effect of anchoring force associated with the large def...According to the tensile failure of rock bolt in weakly cemented soft rock, this paper presents a new segmented anchoring style in order to weaken the cumulative effect of anchoring force associated with the large deformation. Firstly, a segmented mechanical model was established in which free and anchoring section of rock bolt were respectively arranged in different deformation zones. Then, stress and displacement in elastic non-anchoring zone, elastic anchoring zone, elastic sticking zone, softening sticking zone and broken zone were derived respectively based on neural theory and tri-linear strain softening constitutive model of soft rock. Results show that the anchoring effect can be characterized by a supporting parameter b. With its increase, the peak value of tangential stress gradually moves to the roadway wall, and the radial stress significantly increases, which means the decrease of equivalent plastic zone and improvement of confining effect provided by anchorage body. When b increases to 0.72, the equivalent plastic zone disappears, and stresses tend to be the elastic solutions. In addition, the anchoring effect on the displacement of surrounding rock can be quantified by a normalization factor δ.展开更多
Via in situ uniaxial tensile tests in a high-resolution transmission electron microscope,we directly observed a cross-over of plastic deformation mechanisms in a nanocrystalline (nc) Cu thin film containing nano-twin ...Via in situ uniaxial tensile tests in a high-resolution transmission electron microscope,we directly observed a cross-over of plastic deformation mechanisms in a nanocrystalline (nc) Cu thin film containing nano-twin lamellae.For a certain twin lamellae length,the twin lamellae with a larger thickness emit dislocations inclined (Schmidt-factor dislocations,i.e.,S-dislocations) toward the twin boundaries.Upon decreasing the twin lamellae thickness to a critical value,such as approximately 15nm,the plasticity switches toward emission of twinning partial dislocations (T-dislocations) parallel to the twin planes that cause migration of the twin boundaries.The critical twin thickness value also depends on the length of the twin.These results provide direct evidence for thestrengthening and softening mechanisms in nano-twinning structured metals.展开更多
Nanostructured Fe_(40)Ni_(38)Mo_(4)B_(l8) prepared by crystallization technique has a microstructure of nanometer-sized fcc(Fe,Ni)solid solution crystallites embedded in a nanometer-thick amorphous matrix.The nanostru...Nanostructured Fe_(40)Ni_(38)Mo_(4)B_(l8) prepared by crystallization technique has a microstructure of nanometer-sized fcc(Fe,Ni)solid solution crystallites embedded in a nanometer-thick amorphous matrix.The nanostructured Fe_(40)Ni_(38)Mo_(4)B_(l8) obtained at 740K has the optimal soft magnetic properties.The maximal magnetic softening can be understood by considering the combination of the zero anisotropy and the lowest saturation magnetostriction.展开更多
Austenitic stainless steel(ASS) and High nickel steel(HNS) welding consumables are being used for welding Q&T steels, as they have higher solubility for hydrogen in austenitic phase, to avoid hydrogen induced crac...Austenitic stainless steel(ASS) and High nickel steel(HNS) welding consumables are being used for welding Q&T steels, as they have higher solubility for hydrogen in austenitic phase, to avoid hydrogen induced cracking(HIC) but they are very expensive. In recent years, the developments of low hydrogen ferritic steel(LHF) consumables that contain no hygroscopic compounds are utilized for welding Q&T steels. Heat affected zone(HAZ) softening is another critical issue during welding of armour grade Q&T steels and it depends on the welding process employed and the weld thermal cycle. In this investigation an attempt has been made to study the influence of welding consumables and welding processes on metallurgical characteristics of armour grade Q&T steel joints by various metallurgical characterization procedures. Shielded metal arc welding(SMAW) and flux cored arc welding(FCAW) processes were used for making welds using ASS, LHF and HNS welding consumables. The joints fabricated by using LHF consumables offered lower degree of HAZ softening and there is no evidence of HIC in the joints fabricated using LHF consumables.展开更多
In this paper, in order to investigate the viscoelasticity of asphalt binder at the softening point temperature, more than 30 different asphalt binders were selected and tested by dynamic rheological scan method using...In this paper, in order to investigate the viscoelasticity of asphalt binder at the softening point temperature, more than 30 different asphalt binders were selected and tested by dynamic rheological scan method using a dynamic shear rheometer(DSR). The softening points and the rheological parameters of the asphalt samples were measured and analyzed. The results indicated that at the softening point temperature the neat asphalt and the SBS modified asphalt showed two different rheological states. The neat asphalt binders had a majority of viscous components in viscoelastic composition, with the phase angles being mostly higher than 80 o. The SBS modified binders had lower phase angles, with their elasticity still retained. Meanwhile, the Shapiro-Wilk normality test showed that at a confidence level of 0.05, at whatever aging state, the neat asphalt had a stable complex modulus corresponding to the softening point, which was 13.034 kPa at a standard deviation of 2.105 kPa under the same test condition. The softening point of neat asphalt binder can be calculated via the equivalent modulus rule. It is found out that there is a good relationship between the calculated and the measured softening points. And it is suggested that more data are needed to validate this finding.展开更多
Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for wate...Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe3O4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe3O4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.展开更多
The temperature dependent Fe Mossbauer and X-ray diffraction measurement on Bi-system 2:2:2:3 phase have been carried out from 77 K to 300 K. It was found that there are two anomalous behaviors of lattice vibrational ...The temperature dependent Fe Mossbauer and X-ray diffraction measurement on Bi-system 2:2:2:3 phase have been carried out from 77 K to 300 K. It was found that there are two anomalous behaviors of lattice vibrational modes near 125 K and 220 K. This phenomena of lattice softening above Tc is taken as a precursor effect of superconductivity.展开更多
The RMB-150B rock mechanics test system was employed to obtain the complete stress-strain test curves under confining pressures of 0-30MPa for marble samples from Ya'an ,Sichuan province. On the basis of former st...The RMB-150B rock mechanics test system was employed to obtain the complete stress-strain test curves under confining pressures of 0-30MPa for marble samples from Ya'an ,Sichuan province. On the basis of former study and the convention triaxial pressure test results ,the complete procedures curves which described the relationships between yielding strength、 peak strength、 residual strength and confining pressure was obtained. Taking the strain softening of rock into account, the bilinear elastic-linear softening-residual perfect plasticity four-linear model was put forward in this paper on the basis of the test results and theory of plasticity. This model was adopted to describe the behaviors of marble in different phases under triaxial compression with the constitutive equation of strain softening phase as focus. The results indicated that the theoretic model fitted in well with the test results.展开更多
A multi-block model and a corresponding computer program have been developed which predict the kinematics of landslides.Furthermore,a unique event for studying different models simulating the triggering and movement o...A multi-block model and a corresponding computer program have been developed which predict the kinematics of landslides.Furthermore,a unique event for studying different models simulating the triggering and movement of landslides is the 2008Wenchuan earthquake in the mountainous region in Sichuan Province of China,which caused a large number of rapid landslides.The purpose of the paper is two-fold:(a)to propose and incorporate into the multi-block model constitutive relations predicting soil response along slip surfaces,and(b)to apply the multi-block model with the constitutive relations at landslides triggered by the Wenchuan earthquake.The proposed constitutive equations predict the shape of the shear stress-displacement response measured in ring shear tests.In the application,four landslides caused by the Wenchuan earthquake were considered.Only in one of these landslides the shear resistance-displacement response along the slip surface has been measured in laboratory tests.At this landslide,the triggering and movement of the landslide was predicted.In the other landslides,back analyses were performed and it was observed that the multi-block model predicted reasonably well the final configuration of all slides.In addition,as the measured and back-estimated total friction angle of all landslides was less than 180,and the materials along the slip surface were sandy,it is inferred that some,or all of the slip surface during these slides was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and movement of these landslides.Concluding,the paper(A)proposed and validated a multi-block constitutive model which can be applied to predict the triggering and movement of earthquake-induced slides and(B)by analyzing four landslides of the 2008 Wenchuan earthquake,it concludes that some,or all of the slip surface during these slides,was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and movement of these landslides.展开更多
In situ synchrotron angle-dispersive x-ray diffraction experiments on niobium powders have been conducted at pressures up to 61 GPa and room temperature using the diamond anvil cell technique. From the full width at h...In situ synchrotron angle-dispersive x-ray diffraction experiments on niobium powders have been conducted at pressures up to 61 GPa and room temperature using the diamond anvil cell technique. From the full width at half maximum of the measured diffraction lines, the yield strength was derived with the line-width analysis theory. The niobium powder sample was found to be compressed more packed firstly and then yielded at~14 GPa–18 GPa. Following an initial increase in the yield strength with pressure, an obvious decrease was observed occurring at ~42 GPa–47 GPa accompanying with a typical pressure dependence above 47 GPa. The experimentally observed anomalous softening of the yield strength in niobium surprisingly follows the trend of the predicted unusual softening in the shear modulus by the recent theoretical investigations. The possible mechanisms, applicable to interpret the yield strength softening of materials at high pressure,were also discussed in detail.展开更多
This paper, based on the strain softening character of rock, and the de formation feature of roadway with badly damaged surrounding rock and adopting the ideal elastoplastic softening model, derives the formula for ca...This paper, based on the strain softening character of rock, and the de formation feature of roadway with badly damaged surrounding rock and adopting the ideal elastoplastic softening model, derives the formula for calculating the supporting resistance for the roadway. It is pointed out that controlling the rheid speed of the rock in the plastic softening area is critical and that the combined supporting, i. e. combining surrounding rock internal rein forcement with external supporting f is the reasonahle supporting to this kiud of roadways. The theory and practice introduced in this paper are of universal significance for harnessing the roadway with badly damaged surrounding rock.展开更多
The behavior of elastic modulus related with strain amplitude is studied.It was found that modulus behaves softening when internal friction exhibits normal amplitude-dependent effects,while increases slightly with the...The behavior of elastic modulus related with strain amplitude is studied.It was found that modulus behaves softening when internal friction exhibits normal amplitude-dependent effects,while increases slightly with the appearance of anomalously amplitude-dependent eSect.With the decrease of frequency of measurement,the variation of modulus with amplitude becomes small.A trial for obtaining information from amplitude internal friction peak was made on the basis of Debye equations.展开更多
The generalized phonon density of states(PDOS)and the valence electron density of states(EDOS)of the amorphous Fe_(90-x)Co_(x)Zr_(10)(x=4,10 and 40)alloys were measured at the room temperature by inelastic neutron-sca...The generalized phonon density of states(PDOS)and the valence electron density of states(EDOS)of the amorphous Fe_(90-x)Co_(x)Zr_(10)(x=4,10 and 40)alloys were measured at the room temperature by inelastic neutron-scattering and x-ray photoemission spectroscopy,respectively.Preliminary results show that the stronger the Invar effect,the softer is the PDOS in the low-energy region and the larger is the EDOS at the Fermi energy level.The enhancement of electron-phonon interaction was suggested to explain the low-energy phonon softening observed in Invar alloys.展开更多
Nd-doping effects are investigated in TiO_(2)nanoparticles with various annealing temperatures T from 70℃ to 1100℃ by means of x-ray diffraction(XRD)and Raman scattering spectroscopy.XRD results indicate that the sa...Nd-doping effects are investigated in TiO_(2)nanoparticles with various annealing temperatures T from 70℃ to 1100℃ by means of x-ray diffraction(XRD)and Raman scattering spectroscopy.XRD results indicate that the sample shows a rutile phase at 1100℃,which changes to anatase phase at 900℃.With decreasing T down to 300℃,a significant lattice shrink is found,that is,the lattice parameter c is significantly suppressed while the a value shows a gradual decrease.With further decrease of T,the c-value shows an unexpected increase while the a-value keeps a gradual decrease.Thus,a lattice distortion takes place with changing the annealing temperature.In Raman investigation,all the Raman modes for the anatase phase show hardening behaviors with decreasing T in the range 900-300℃,and then the Eg and A1g modes show softening behaviors below 300℃,suggesting the variation of the lattice distortion.The variation of the lattice distortion at different annealing temperatures is ascribed to different depositions of Nd ions on the surface of TiO_(2)nanoparticles.展开更多
Elliptic flow for non-central Au＋Au collisions at √SNN=200 GeV is investigated with a 2＋1 dimensional hydrodynamic model. We analyze the softening effect by the velocity along the axis. The contribution of the elli...Elliptic flow for non-central Au＋Au collisions at √SNN=200 GeV is investigated with a 2＋1 dimensional hydrodynamic model. We analyze the softening effect by the velocity along the axis. The contribution of the elliptic flow from the QGP phase, mixed phase and hadron gas phase is studied. The relation between the sound horizon and evolution of the elliptic flow is discussed.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12274471 and 11922415)Guangdong Basic and Applied Basic Research Foundation(Grant No.2022A1515011168)+3 种基金the Key Research&Development Program of Guangdong Province,China(Grant No.2019B110209003)the Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant Nos.2022B1212010008)Lingyong Zeng was supported by the Postdoctoral Fellowship Program of CPSF(Grant Nos.GZC20233299)Fundamental Research Funds for the Central Universities,Sun Yat-Sen University(Grant Nos.29000-31610058)。
文摘Chemical doping is a critical factor in the development of new superconductors or optimizing the superconducting transition temperature(T_(c))of the parent superconducting materials.Here,a new simple urea approach is developed to synthesize the N-dopedα-Mo_(2)C.Benefiting from the simple urea method,a broad superconducting dome is found in the Mo_(2)C_(1−x)N_(x)(0≤x≤0.49)compositions.X-ray diffraction results show that the structure of𝛼α-Mo_(2)C remains unchanged and there is a variation of lattice parameters with nitrogen doping.Resistivity,magnetic susceptibility,and heat capacity measurement results confirm that T_(c)was strongly increased from 2.68K(x=0)to 7.05K(x=0.49).First-principles calculations and our analysis indicate that increasing nitrogen doping leads to a rise in the density of states at the Fermi level and doping-induced phonon softening,which enhances electron–phonon coupling.This results in an increase in𝑇T_(c)and a sharp rise in the upper critical field.Our findings provide a promising strategy for fabricating transition metal carbonitrides and provide a material platform for further study of the superconductivity of transition metal carbides.
基金sponsored by the Alpha Foundation for the Improvement of Mine Safety and Health, Inc. (Alpha Foundation)the funding provided for this project by the Alpha Foundationpartially funded by the National Institute of Occupational Health and Science (NIOSH) under Grant Number 200-2016-90154.
文摘Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and operations.Previous studies have identified that discontinuous,layered roof materials have some self-supporting capacity.This research is a preliminary step towards understanding these mechanics in coal-measure rocks.Although others have considered broad conceptual models and simplified analogs for mine roof behavior,this study presents a unique numerical model that more completely represents in-situ roof conditions.The discrete element method(DEM)is utilized to conduct a parametric analysis considering a range of in-situ stress ratios,material properties,and joint networks to determine the parameters controlling the stability of single-entries modeled in two-dimensions.Model results are compared to empirical observations of roof-support effectiveness(ARBS)in the context of the coal mine roof rating(CMRR)system.Results such as immediate roof displacement,overall stability,and statistical relationships between model parameters and outcomes are presented herein.Potential practical applications of this line of research include:(1)roof-support optimization for a range of coal-measure rocks,(2)establishment of a relationship between roof stability and pillar stress,and(3)determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.
基金the Science Foundation of China Academy of Engineering Physics,Contract No.9301002.
文摘Optical analyzer technique are used to measure the sound speed as a function of pressure for shocked multiphase alloy 93 W containing 93%W, with 4.2%Ni-2.45%Fe-0.35%Co alloy as binder, all in wt.%. Below 250 GPa, the speed increases with pressure, then a bulk“softening” process occurs at 250 to 340 GPa, afterwards the speed again rises with pressure and coincides with the calculated bulk sound speed, showing a fluid-like behavior for this alloy. Lindemann melting law calculations were made for both the binder and the tungsten. The results showed that 250 GPa corresponds approximately to the pressure for the binder beginning to melt, and 340GPa corresponds to that for tungsten. Therefore, we believe that the shock-induced “softening” mechanism for this kind of multiphase alloys can be attributed to the binder melting.
基金Supported by the National Natural Science Foundation of China(Grant Nos.12122405,51632002,and 11974133)the Program for Changjiang Scholars and Innovative Research Team in Universities(Grant No.IRT 15R23)+1 种基金financial support from the Engineering and Physical Sciences Research Council(Grant No.EP/P022596/1)。
文摘Sulfur and lanthanum hydrides under compression display superconducting states with high observed critical temperatures.It has been recently demonstrated that carbonaceous sulfur hydride displays room temperature superconductivity.However,this phenomenon has been observed only at very high pressure.Here,we theoretically search for superconductors with very high critical temperatures,but at much lower pressures.We describe two of such sodalite-type clathrate hydrides,YbH6 and LuH6.These hydrides are metastable and are predicted to superconduct with T_(c)~145 K at 70 GPa and T_(c)~273 K at 100 GPa,respectively.This striking result is a consequence of the strong interrelationship between the f states present at the Fermi level,structural stability,and the final T_(c) value.For example,TmH6,with unfilled 4f orbitals,is stable at 50 GPa,but has a relatively low value of T_(c) of 25 K.The YbH6 and LuH6 compounds,with their filled f-shells,exhibit prominent phonon"softening",which leads to a strong electron-phonon coupling,and as a result,an increase in T_(c).
基金a part of the 12th Five Year Plan Project(No.ESC 0105),acronymed as‘‘De Coal Art”
文摘In some of the coalfields in India, coal seams are only developed but no extraction of pillars is possible due to the presence of surface or sub-surface structures and also non-availability of stowing materials which leads to huge amounts of coal being locked-up underground. Spontaneous heating and fire, accumulation of poisonous gases, severe stability issues leading to unsafe workings and environmental hazards are the major problems associated with the developed coal pillars. So, there is a pressing need for a technology for the mining industry to extract the huge amount of coal locked-up under different constraints. In this study, the locked-up coal is proposed to be extracted by artificially strengthening the rib pillars. The detailed comparative study is carried out to know the increase of extraction percentage of locked-up coal by strengthening the rib pillars with FRP. Extraction methodology is designed and studied through numerical modelling for its stability analysis to evaluate its suitability of application in underground.
基金Financial support for this work was provided by the Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents of China(No.2015RCJJ042)the National Natural Science Foundation of China(Nos.41472280,51274133)+1 种基金the Promotive Research Fund for Excellent Young and Middle-aged Scientisits of Shandong Province of China(No.BS2015SF005)the Opening Project Fund of Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation(No.CDPM2013KF05)
文摘According to the tensile failure of rock bolt in weakly cemented soft rock, this paper presents a new segmented anchoring style in order to weaken the cumulative effect of anchoring force associated with the large deformation. Firstly, a segmented mechanical model was established in which free and anchoring section of rock bolt were respectively arranged in different deformation zones. Then, stress and displacement in elastic non-anchoring zone, elastic anchoring zone, elastic sticking zone, softening sticking zone and broken zone were derived respectively based on neural theory and tri-linear strain softening constitutive model of soft rock. Results show that the anchoring effect can be characterized by a supporting parameter b. With its increase, the peak value of tangential stress gradually moves to the roadway wall, and the radial stress significantly increases, which means the decrease of equivalent plastic zone and improvement of confining effect provided by anchorage body. When b increases to 0.72, the equivalent plastic zone disappears, and stresses tend to be the elastic solutions. In addition, the anchoring effect on the displacement of surrounding rock can be quantified by a normalization factor δ.
基金Supported by the National Nature Science Foundation of China(10825419,50831001)the National Basic Research Program of China(2009CB623700)。
文摘Via in situ uniaxial tensile tests in a high-resolution transmission electron microscope,we directly observed a cross-over of plastic deformation mechanisms in a nanocrystalline (nc) Cu thin film containing nano-twin lamellae.For a certain twin lamellae length,the twin lamellae with a larger thickness emit dislocations inclined (Schmidt-factor dislocations,i.e.,S-dislocations) toward the twin boundaries.Upon decreasing the twin lamellae thickness to a critical value,such as approximately 15nm,the plasticity switches toward emission of twinning partial dislocations (T-dislocations) parallel to the twin planes that cause migration of the twin boundaries.The critical twin thickness value also depends on the length of the twin.These results provide direct evidence for thestrengthening and softening mechanisms in nano-twinning structured metals.
基金Supported in part by the National Natural Science Foundation of China under Grant No.59772039the State Key Laboratory of the Rapidly Solidified Alloys+1 种基金the Applied Magnetism Laboratory of the Education Ministrythe Natural Science Foundation of Gansu Province.
文摘Nanostructured Fe_(40)Ni_(38)Mo_(4)B_(l8) prepared by crystallization technique has a microstructure of nanometer-sized fcc(Fe,Ni)solid solution crystallites embedded in a nanometer-thick amorphous matrix.The nanostructured Fe_(40)Ni_(38)Mo_(4)B_(l8) obtained at 740K has the optimal soft magnetic properties.The maximal magnetic softening can be understood by considering the combination of the zero anisotropy and the lowest saturation magnetostriction.
基金Armament Research Board (ARMREB), New Delhi for funding this project work (Project no. MAA/03/ 41)
文摘Austenitic stainless steel(ASS) and High nickel steel(HNS) welding consumables are being used for welding Q&T steels, as they have higher solubility for hydrogen in austenitic phase, to avoid hydrogen induced cracking(HIC) but they are very expensive. In recent years, the developments of low hydrogen ferritic steel(LHF) consumables that contain no hygroscopic compounds are utilized for welding Q&T steels. Heat affected zone(HAZ) softening is another critical issue during welding of armour grade Q&T steels and it depends on the welding process employed and the weld thermal cycle. In this investigation an attempt has been made to study the influence of welding consumables and welding processes on metallurgical characteristics of armour grade Q&T steel joints by various metallurgical characterization procedures. Shielded metal arc welding(SMAW) and flux cored arc welding(FCAW) processes were used for making welds using ASS, LHF and HNS welding consumables. The joints fabricated by using LHF consumables offered lower degree of HAZ softening and there is no evidence of HIC in the joints fabricated using LHF consumables.
基金financially supported by the Shandong Natural Science Foundation (ZR2009FL020)the Shandong Transportation Innovation Foundation (2010Y20)
文摘In this paper, in order to investigate the viscoelasticity of asphalt binder at the softening point temperature, more than 30 different asphalt binders were selected and tested by dynamic rheological scan method using a dynamic shear rheometer(DSR). The softening points and the rheological parameters of the asphalt samples were measured and analyzed. The results indicated that at the softening point temperature the neat asphalt and the SBS modified asphalt showed two different rheological states. The neat asphalt binders had a majority of viscous components in viscoelastic composition, with the phase angles being mostly higher than 80 o. The SBS modified binders had lower phase angles, with their elasticity still retained. Meanwhile, the Shapiro-Wilk normality test showed that at a confidence level of 0.05, at whatever aging state, the neat asphalt had a stable complex modulus corresponding to the softening point, which was 13.034 kPa at a standard deviation of 2.105 kPa under the same test condition. The softening point of neat asphalt binder can be calculated via the equivalent modulus rule. It is found out that there is a good relationship between the calculated and the measured softening points. And it is suggested that more data are needed to validate this finding.
基金supported by international cooperation program for science and technology funded by the Ministry of Science,ICT&Future Planning(NRF-2014K1A3A1A09063208)
文摘Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe3O4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe3O4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.
文摘The temperature dependent Fe Mossbauer and X-ray diffraction measurement on Bi-system 2:2:2:3 phase have been carried out from 77 K to 300 K. It was found that there are two anomalous behaviors of lattice vibrational modes near 125 K and 220 K. This phenomena of lattice softening above Tc is taken as a precursor effect of superconductivity.
文摘The RMB-150B rock mechanics test system was employed to obtain the complete stress-strain test curves under confining pressures of 0-30MPa for marble samples from Ya'an ,Sichuan province. On the basis of former study and the convention triaxial pressure test results ,the complete procedures curves which described the relationships between yielding strength、 peak strength、 residual strength and confining pressure was obtained. Taking the strain softening of rock into account, the bilinear elastic-linear softening-residual perfect plasticity four-linear model was put forward in this paper on the basis of the test results and theory of plasticity. This model was adopted to describe the behaviors of marble in different phases under triaxial compression with the constitutive equation of strain softening phase as focus. The results indicated that the theoretic model fitted in well with the test results.
基金The National Key R＆D Program of China (2017YFC1502903) Sichuan International Cooperation and Exchange for Science and Technology (2016HH0079)+1 种基金 ＂Novel methodologies for the assessment of risk of ground displacement＂ under ESPA 2007-2013 of Greece under
文摘A multi-block model and a corresponding computer program have been developed which predict the kinematics of landslides.Furthermore,a unique event for studying different models simulating the triggering and movement of landslides is the 2008Wenchuan earthquake in the mountainous region in Sichuan Province of China,which caused a large number of rapid landslides.The purpose of the paper is two-fold:(a)to propose and incorporate into the multi-block model constitutive relations predicting soil response along slip surfaces,and(b)to apply the multi-block model with the constitutive relations at landslides triggered by the Wenchuan earthquake.The proposed constitutive equations predict the shape of the shear stress-displacement response measured in ring shear tests.In the application,four landslides caused by the Wenchuan earthquake were considered.Only in one of these landslides the shear resistance-displacement response along the slip surface has been measured in laboratory tests.At this landslide,the triggering and movement of the landslide was predicted.In the other landslides,back analyses were performed and it was observed that the multi-block model predicted reasonably well the final configuration of all slides.In addition,as the measured and back-estimated total friction angle of all landslides was less than 180,and the materials along the slip surface were sandy,it is inferred that some,or all of the slip surface during these slides was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and movement of these landslides.Concluding,the paper(A)proposed and validated a multi-block constitutive model which can be applied to predict the triggering and movement of earthquake-induced slides and(B)by analyzing four landslides of the 2008 Wenchuan earthquake,it concludes that some,or all of the slip surface during these slides,was sheared in an undrained manner and excess pore pressures generated during sliding played a key role in the triggering and movement of these landslides.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1530134,U1730248,11772312,and 11504354)
文摘In situ synchrotron angle-dispersive x-ray diffraction experiments on niobium powders have been conducted at pressures up to 61 GPa and room temperature using the diamond anvil cell technique. From the full width at half maximum of the measured diffraction lines, the yield strength was derived with the line-width analysis theory. The niobium powder sample was found to be compressed more packed firstly and then yielded at~14 GPa–18 GPa. Following an initial increase in the yield strength with pressure, an obvious decrease was observed occurring at ~42 GPa–47 GPa accompanying with a typical pressure dependence above 47 GPa. The experimentally observed anomalous softening of the yield strength in niobium surprisingly follows the trend of the predicted unusual softening in the shear modulus by the recent theoretical investigations. The possible mechanisms, applicable to interpret the yield strength softening of materials at high pressure,were also discussed in detail.
文摘This paper, based on the strain softening character of rock, and the de formation feature of roadway with badly damaged surrounding rock and adopting the ideal elastoplastic softening model, derives the formula for calculating the supporting resistance for the roadway. It is pointed out that controlling the rheid speed of the rock in the plastic softening area is critical and that the combined supporting, i. e. combining surrounding rock internal rein forcement with external supporting f is the reasonahle supporting to this kiud of roadways. The theory and practice introduced in this paper are of universal significance for harnessing the roadway with badly damaged surrounding rock.
文摘The behavior of elastic modulus related with strain amplitude is studied.It was found that modulus behaves softening when internal friction exhibits normal amplitude-dependent effects,while increases slightly with the appearance of anomalously amplitude-dependent eSect.With the decrease of frequency of measurement,the variation of modulus with amplitude becomes small.A trial for obtaining information from amplitude internal friction peak was made on the basis of Debye equations.
文摘The generalized phonon density of states(PDOS)and the valence electron density of states(EDOS)of the amorphous Fe_(90-x)Co_(x)Zr_(10)(x=4,10 and 40)alloys were measured at the room temperature by inelastic neutron-scattering and x-ray photoemission spectroscopy,respectively.Preliminary results show that the stronger the Invar effect,the softer is the PDOS in the low-energy region and the larger is the EDOS at the Fermi energy level.The enhancement of electron-phonon interaction was suggested to explain the low-energy phonon softening observed in Invar alloys.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10874087,11074124 and 10904052,Jiangsu Provincial Natural Science Foundation under Grant No 200921555the China Postdoctoral Science Foundation under Grant No 201003575.
文摘Nd-doping effects are investigated in TiO_(2)nanoparticles with various annealing temperatures T from 70℃ to 1100℃ by means of x-ray diffraction(XRD)and Raman scattering spectroscopy.XRD results indicate that the sample shows a rutile phase at 1100℃,which changes to anatase phase at 900℃.With decreasing T down to 300℃,a significant lattice shrink is found,that is,the lattice parameter c is significantly suppressed while the a value shows a gradual decrease.With further decrease of T,the c-value shows an unexpected increase while the a-value keeps a gradual decrease.Thus,a lattice distortion takes place with changing the annealing temperature.In Raman investigation,all the Raman modes for the anatase phase show hardening behaviors with decreasing T in the range 900-300℃,and then the Eg and A1g modes show softening behaviors below 300℃,suggesting the variation of the lattice distortion.The variation of the lattice distortion at different annealing temperatures is ascribed to different depositions of Nd ions on the surface of TiO_(2)nanoparticles.
基金supported by the Heilongjiang Province Natural Science Foundation of China(No.A200814)
文摘Elliptic flow for non-central Au＋Au collisions at √SNN=200 GeV is investigated with a 2＋1 dimensional hydrodynamic model. We analyze the softening effect by the velocity along the axis. The contribution of the elliptic flow from the QGP phase, mixed phase and hadron gas phase is studied. The relation between the sound horizon and evolution of the elliptic flow is discussed.
