Although pressure cells have been produced and installed successfully for decades,the accuracy of measured pressure is often inadequate.Due to large differences between the stiffness of pressure cells and the surround...Although pressure cells have been produced and installed successfully for decades,the accuracy of measured pressure is often inadequate.Due to large differences between the stiffness of pressure cells and the surrounding media,there is a considerable difference between applied pressure and that measured from pressure cells.It is often difficult and expensive to make a pressure cell with stiffness（modulus of elasticity） similar to the surrounding material in which it will be embedded.In order to improve this situation,a casing material with proportional dimensions is recommended as a means to obtain reliable results.In our study,the effect of using casing in the installation of pressure cells is investigated,providing the characteristics of casing.Some practical recommendations are presented to improve the accuracy of the results using casing.展开更多
It is important to be able to measure stresses in tunnel linings to verify design assumptions and validate numerical models.For sprayed concrete-lined tunnels,continuous monitoring of stresses from the time of sprayin...It is important to be able to measure stresses in tunnel linings to verify design assumptions and validate numerical models.For sprayed concrete-lined tunnels,continuous monitoring of stresses from the time of spraying onwards is desirable,and this can only be achieved using pressure cells installed on and in the sprayed concrete lining.Although there has been some success in using radial pressure cells between the ground and the lining,a method for obtaining reliable absolute values of stress from tangential pressure cells embedded in the sprayed concrete has not been available.This paper describes numerical and experimental studies of the behavior of pressure cells for monitoring stresses in a sprayed concrete lining and describes an original methodology to achieve reliable results.In particular,data from tangential pressure cells require careful interpretation,as they are sensitive to temperature,and this temperature sensitivity is found in parametric numerical analyses to vary as the stiffness of the concrete and its coefficient of thermal expansion evolve at early age.Tangential pressure cells are also sensitive to shrinkage strains in the concrete,and a methodology for removing this effect is described.Using the approach described in this paper,it is now possible to use pressure cells to measure absolute values of stresses in and on sprayed concrete tunnel linings from early age into the long-term.An example of radial and tangential pressure cells installed in the Heathrow Terminal 4 concourse tunnel is used to illustrate the methodology.展开更多
Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China＇s Mianyang research reactor. We achieve a high-pressure condi...Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China＇s Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi（Ⅰ–Ⅱ 2.55 GPa, Ⅱ–V 7.7 GPa） are observed at 100 and 300 kN, respectively, by resistance measurements.The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth.As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm^3.展开更多
The homogenization of silicate melt inclusions （SMIs）,small droplets of silicate melt trapped in magmatic minerals,is an important component of petrogenetic and magmatic research.Conventional homogenization experime...The homogenization of silicate melt inclusions （SMIs）,small droplets of silicate melt trapped in magmatic minerals,is an important component of petrogenetic and magmatic research.Conventional homogenization experiments on SMIs use microscope-mounted heating stages capable of producing high temperatures at 1 atm and cold-seal high-pressure vessels.Heating stages are generally used for SMIs with low internal pressures and allow in situ observations of the homogenization processes.In contrast,cold-seal high-pressure vessels are generally used to heat SMIs that have high internal pressures,although the homogenized SMIs can only be observed after quenching in this approach.Here we outline an alternative approach that uses a hydrothermal diamond anvil cell （HDAC） apparatus to homogenize SMIs.This is the only current method wherein phase changes in high-internal-pressure SMIs can be observed in situ during homogenization experiments,which represents an advantage over other conventional methods.Using an HDAC apparatus prevents high-internal-pressure SMIs from decrepitating during heating by elevating their external pressure,in addition to allowing in situ observations of SMIs.The type-V HDAC that is currently being used has a shorter distance between the sample chamber and the observation window than earlier types,potentially enabling continuous observation of the processes involved in heating and SMI homogenization through an objective lens with a long working distance.Homogenization experiments using HDAC require that a number of steps,including HDAC preparation,sample preparation,sample loading,preheating,and formal heating,be carefully followed.Homogenization experiments on SMIs within granite samples from the Jiajika pegmatite deposit （Sichuan,China） are best performed using an HDAC-based approach,because the elevated proper external pressure of these SMIs,combined with a short heating duration,helps to suppress material leakage and any reactions within the SMIs,in addition to allowing in situ observations during homogenization experiments.Furthermore,using the HDAC approach has other benefits：heating rates can be precisely controlled,wafer oxidization can be prevented,and samples can be subjected to in situ microbeam analysis.In summary,homogenization using HDAC provides more reliable results than those obtained using conventional heating equipment.Future developments will include improvements to the quenching method and temperature controls for the HDAC apparatus,thereby improving the utility of this approach for SMI homogenization experiments.展开更多
A high-order Lagrangian cell-centered conservative gas dynamics scheme is presented on unstructured meshes. A high-order piecewise pressure of the cell is intro- duced. With the high-order piecewise pressure of the ce...A high-order Lagrangian cell-centered conservative gas dynamics scheme is presented on unstructured meshes. A high-order piecewise pressure of the cell is intro- duced. With the high-order piecewise pressure of the cell, the high-order spatial discretiza- tion fluxes are constructed. The time discretization of the spatial fluxes is performed by means of the Taylor expansions of the spatial discretization fluxes. The vertex velocities are evaluated in a consistent manner due to an original solver located at the nodes by means of momentum conservation. Many numerical tests are presented to demonstrate the robustness and the accuracy of the scheme.展开更多
This paper presents a Lagrangian cell-centered conservative gas dynamics scheme. The piecewise constant pressures of cells arising from the current time sub-cell densities and the current time isentropic speed of soun...This paper presents a Lagrangian cell-centered conservative gas dynamics scheme. The piecewise constant pressures of cells arising from the current time sub-cell densities and the current time isentropic speed of sound are introduced. Multipling the initial cell density by the initial sub-cell volumes obtains the sub-cell Lagrangian masses, and dividing the masses by the current time sub-cell volumes gets the current time sub- cell densities. By the current time piecewise constant pressures of cells, a scheme that conserves the momentum and total energy is constructed. The vertex velocities and the numerical fluxes through the cell interfaces are computed in a consistent manner due to an original solver located at the nodes. The numerical tests are presented, which are representative for compressible flows and demonstrate the robustness and accuracy of the Lagrangian cell-centered conservative scheme.展开更多
This article summarizes the developments of experimental techniques for high pressure x-ray diffraction（XRD） in diamond anvil cells（DACs） using synchrotron radiation. Basic principles and experimental methods for ...This article summarizes the developments of experimental techniques for high pressure x-ray diffraction（XRD） in diamond anvil cells（DACs） using synchrotron radiation. Basic principles and experimental methods for various diffraction geometry are described, including powder diffraction, single crystal diffraction, radial diffraction, as well as coupling with laser heating system. Resolution in d-spacing of different diffraction modes is discussed. More recent progress, such as extended application of single crystal diffraction for measurements of multigrain and electron density distribution, timeresolved diffraction with dynamic DAC and development of modulated heating techniques are briefly introduced. The current status of the high pressure beamline at BSRF（Beijing Synchrotron Radiation Facility） and some results are also presented.展开更多
Research on the melting phenomenon is the most challenging work in the high pressure/temperature field. Until now,large discrepancies still exist in the melting curve of iron, the most interesting and extensively stud...Research on the melting phenomenon is the most challenging work in the high pressure/temperature field. Until now,large discrepancies still exist in the melting curve of iron, the most interesting and extensively studied element in geoscience research. Here we present a summary about techniques detecting melting in the laser heating diamond anvil cell.展开更多
A system for the investigation of the magnetic properties of materials under high pressure is fabricated based on diamond anvil cell （DAC） technology. The system is designed with an improved coil arranged around the...A system for the investigation of the magnetic properties of materials under high pressure is fabricated based on diamond anvil cell （DAC） technology. The system is designed with an improved coil arranged around the diamond of a non-magnetic DAC. Using this system, the magnetic transition of ferromagnetic （Fe） sample under increasing pressure can be observed. We successfully obtain the evolution of magnetic properties as a function of applied pressure reaching 26.9 GPa in the Fe sample. A magnetic transition is observed at approximately 13 GPa, which is consistent with the theoretical prediction.展开更多
The finite difference method and the volume of fluid （VOF） method were used to develop a three-dimensional numerical model to study wave interaction with a perforated caisson. The partial cell method was adopted to ...The finite difference method and the volume of fluid （VOF） method were used to develop a three-dimensional numerical model to study wave interaction with a perforated caisson. The partial cell method was adopted to solve this type of problem for the first time. The validity of the present model, with and without the presence of caisson structures, was examined by comparing the model results with experimental data. Then, the numerical model was used to investigate the effects of various wave and structure parameters on the wave force and wave runup of the perforated quasi-ellipse caisson. Compared with the solid quasi-ellipse caisson, the wave force on the perforated quasi-ellipse caisson is significantly reduced with increasing porosity of the perforated quasi-ellipse caisson. Furthermore, the perforated quasi-ellipse caisson can also reduce the wave runup, and it tends to decrease with the increase of the porosity of the perforated quasi-ellipse caisson and the relative wave height.展开更多
In order to research the characteristic and mechanism of fracture of rock-like materials,the morphology of rock fracture surface under the breakages of uniaxial compression and triaxial compression was observed and me...In order to research the characteristic and mechanism of fracture of rock-like materials,the morphology of rock fracture surface under the breakages of uniaxial compression and triaxial compression was observed and measured by means of a new-type 3D laser scanning system.Based on geographic information system(GIS)technique,the fracture surfaces were 3D visualized and reestablished.According to GIS 3D statistics,the geometrical characteristics of fracture surfaces under different breakage conditions were analyzed,and then based on fractal theory,the change laws of fractal dimension of fracture surfaces were discussed under the conditions of different cell pressures and initial water contents of rock.Furthermore,the relationships between characteristics of fracture surface and mechanical properties of rock were discussed.The results indicate that cell pressure,initial water content,and mechanical parameters of rock are the important factors to influence on the geometrical characteristics of fracture surface.The research provides a new experimental method for quantitative study on the fracture characteristics of various materials under different breakage conditions.展开更多
All existing proton exchange membrane （PEM） fuel cell gas flow fields have been designed on the basis of single-phase gas flow distribution. The presence of liquid water in the flow causes non-uniform gas distributi...All existing proton exchange membrane （PEM） fuel cell gas flow fields have been designed on the basis of single-phase gas flow distribution. The presence of liquid water in the flow causes non-uniform gas distribution, leading to poor cell performance. This paper demonstrates that a gas flow restrictor/distributor, as is commonly used in two-phase flow to stabilize multiphase transport lines and multiphase reactors, can improve the gas flow distribution by significantly reducing gas real-distribution caused by either non-uniform water formation in parallel flow channels or flow instability associated with negative-slope pressure drop characteristic of two-phase horizontal flow systems.展开更多
文摘Although pressure cells have been produced and installed successfully for decades,the accuracy of measured pressure is often inadequate.Due to large differences between the stiffness of pressure cells and the surrounding media,there is a considerable difference between applied pressure and that measured from pressure cells.It is often difficult and expensive to make a pressure cell with stiffness（modulus of elasticity） similar to the surrounding material in which it will be embedded.In order to improve this situation,a casing material with proportional dimensions is recommended as a means to obtain reliable results.In our study,the effect of using casing in the installation of pressure cells is investigated,providing the characteristics of casing.Some practical recommendations are presented to improve the accuracy of the results using casing.
文摘It is important to be able to measure stresses in tunnel linings to verify design assumptions and validate numerical models.For sprayed concrete-lined tunnels,continuous monitoring of stresses from the time of spraying onwards is desirable,and this can only be achieved using pressure cells installed on and in the sprayed concrete lining.Although there has been some success in using radial pressure cells between the ground and the lining,a method for obtaining reliable absolute values of stress from tangential pressure cells embedded in the sprayed concrete has not been available.This paper describes numerical and experimental studies of the behavior of pressure cells for monitoring stresses in a sprayed concrete lining and describes an original methodology to achieve reliable results.In particular,data from tangential pressure cells require careful interpretation,as they are sensitive to temperature,and this temperature sensitivity is found in parametric numerical analyses to vary as the stiffness of the concrete and its coefficient of thermal expansion evolve at early age.Tangential pressure cells are also sensitive to shrinkage strains in the concrete,and a methodology for removing this effect is described.Using the approach described in this paper,it is now possible to use pressure cells to measure absolute values of stresses in and on sprayed concrete tunnel linings from early age into the long-term.An example of radial and tangential pressure cells installed in the Heathrow Terminal 4 concourse tunnel is used to illustrate the methodology.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFA0401503the Science Challenge Project under Grant No TZ2016001the National Natural Science Foundation of China under Grant No 11427810
文摘Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China＇s Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi（Ⅰ–Ⅱ 2.55 GPa, Ⅱ–V 7.7 GPa） are observed at 100 and 300 kN, respectively, by resistance measurements.The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth.As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm^3.
基金supported by the Chinese SinoProbe Project (SinoProbe-03-01)the National Natural Science Foundation of China (41372088)the China Geological Survey Program (1212011220805)
文摘The homogenization of silicate melt inclusions （SMIs）,small droplets of silicate melt trapped in magmatic minerals,is an important component of petrogenetic and magmatic research.Conventional homogenization experiments on SMIs use microscope-mounted heating stages capable of producing high temperatures at 1 atm and cold-seal high-pressure vessels.Heating stages are generally used for SMIs with low internal pressures and allow in situ observations of the homogenization processes.In contrast,cold-seal high-pressure vessels are generally used to heat SMIs that have high internal pressures,although the homogenized SMIs can only be observed after quenching in this approach.Here we outline an alternative approach that uses a hydrothermal diamond anvil cell （HDAC） apparatus to homogenize SMIs.This is the only current method wherein phase changes in high-internal-pressure SMIs can be observed in situ during homogenization experiments,which represents an advantage over other conventional methods.Using an HDAC apparatus prevents high-internal-pressure SMIs from decrepitating during heating by elevating their external pressure,in addition to allowing in situ observations of SMIs.The type-V HDAC that is currently being used has a shorter distance between the sample chamber and the observation window than earlier types,potentially enabling continuous observation of the processes involved in heating and SMI homogenization through an objective lens with a long working distance.Homogenization experiments using HDAC require that a number of steps,including HDAC preparation,sample preparation,sample loading,preheating,and formal heating,be carefully followed.Homogenization experiments on SMIs within granite samples from the Jiajika pegmatite deposit （Sichuan,China） are best performed using an HDAC-based approach,because the elevated proper external pressure of these SMIs,combined with a short heating duration,helps to suppress material leakage and any reactions within the SMIs,in addition to allowing in situ observations during homogenization experiments.Furthermore,using the HDAC approach has other benefits：heating rates can be precisely controlled,wafer oxidization can be prevented,and samples can be subjected to in situ microbeam analysis.In summary,homogenization using HDAC provides more reliable results than those obtained using conventional heating equipment.Future developments will include improvements to the quenching method and temperature controls for the HDAC apparatus,thereby improving the utility of this approach for SMI homogenization experiments.
基金supported by the National Natural Science Foundation of China(Nos.11172050,11372051,and 11001027)
文摘A high-order Lagrangian cell-centered conservative gas dynamics scheme is presented on unstructured meshes. A high-order piecewise pressure of the cell is intro- duced. With the high-order piecewise pressure of the cell, the high-order spatial discretiza- tion fluxes are constructed. The time discretization of the spatial fluxes is performed by means of the Taylor expansions of the spatial discretization fluxes. The vertex velocities are evaluated in a consistent manner due to an original solver located at the nodes by means of momentum conservation. Many numerical tests are presented to demonstrate the robustness and the accuracy of the scheme.
基金supported by the National Natural Science Foundation of China (No. 11172050)
文摘This paper presents a Lagrangian cell-centered conservative gas dynamics scheme. The piecewise constant pressures of cells arising from the current time sub-cell densities and the current time isentropic speed of sound are introduced. Multipling the initial cell density by the initial sub-cell volumes obtains the sub-cell Lagrangian masses, and dividing the masses by the current time sub-cell volumes gets the current time sub- cell densities. By the current time piecewise constant pressures of cells, a scheme that conserves the momentum and total energy is constructed. The vertex velocities and the numerical fluxes through the cell interfaces are computed in a consistent manner due to an original solver located at the nodes. The numerical tests are presented, which are representative for compressible flows and demonstrate the robustness and accuracy of the Lagrangian cell-centered conservative scheme.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10875142,11079040,and 11075175)The 4W2 beamline of BSRF was supported by the Chinese Academy of Sciences(Grant Nos.KJCX2-SW-N20,KJCX2-SW-N03,and SYGNS04)
文摘This article summarizes the developments of experimental techniques for high pressure x-ray diffraction（XRD） in diamond anvil cells（DACs） using synchrotron radiation. Basic principles and experimental methods for various diffraction geometry are described, including powder diffraction, single crystal diffraction, radial diffraction, as well as coupling with laser heating system. Resolution in d-spacing of different diffraction modes is discussed. More recent progress, such as extended application of single crystal diffraction for measurements of multigrain and electron density distribution, timeresolved diffraction with dynamic DAC and development of modulated heating techniques are briefly introduced. The current status of the high pressure beamline at BSRF（Beijing Synchrotron Radiation Facility） and some results are also presented.
文摘Research on the melting phenomenon is the most challenging work in the high pressure/temperature field. Until now,large discrepancies still exist in the melting curve of iron, the most interesting and extensively studied element in geoscience research. Here we present a summary about techniques detecting melting in the laser heating diamond anvil cell.
基金Project supported by the Open Project of State Key Laboratory of Superhard Materials(Jilin University),China(Grant No.201106)
文摘A system for the investigation of the magnetic properties of materials under high pressure is fabricated based on diamond anvil cell （DAC） technology. The system is designed with an improved coil arranged around the diamond of a non-magnetic DAC. Using this system, the magnetic transition of ferromagnetic （Fe） sample under increasing pressure can be observed. We successfully obtain the evolution of magnetic properties as a function of applied pressure reaching 26.9 GPa in the Fe sample. A magnetic transition is observed at approximately 13 GPa, which is consistent with the theoretical prediction.
基金supported by the National Natural Science Foundation of China (Grant No. 50921001)the Science and Technology Program for Communications Construction in West China,of the Ministry of Transport of the People’s Republic of China (Grant No. 2004-328-832-51)
文摘The finite difference method and the volume of fluid （VOF） method were used to develop a three-dimensional numerical model to study wave interaction with a perforated caisson. The partial cell method was adopted to solve this type of problem for the first time. The validity of the present model, with and without the presence of caisson structures, was examined by comparing the model results with experimental data. Then, the numerical model was used to investigate the effects of various wave and structure parameters on the wave force and wave runup of the perforated quasi-ellipse caisson. Compared with the solid quasi-ellipse caisson, the wave force on the perforated quasi-ellipse caisson is significantly reduced with increasing porosity of the perforated quasi-ellipse caisson. Furthermore, the perforated quasi-ellipse caisson can also reduce the wave runup, and it tends to decrease with the increase of the porosity of the perforated quasi-ellipse caisson and the relative wave height.
文摘In order to research the characteristic and mechanism of fracture of rock-like materials,the morphology of rock fracture surface under the breakages of uniaxial compression and triaxial compression was observed and measured by means of a new-type 3D laser scanning system.Based on geographic information system(GIS)technique,the fracture surfaces were 3D visualized and reestablished.According to GIS 3D statistics,the geometrical characteristics of fracture surfaces under different breakage conditions were analyzed,and then based on fractal theory,the change laws of fractal dimension of fracture surfaces were discussed under the conditions of different cell pressures and initial water contents of rock.Furthermore,the relationships between characteristics of fracture surface and mechanical properties of rock were discussed.The results indicate that cell pressure,initial water content,and mechanical parameters of rock are the important factors to influence on the geometrical characteristics of fracture surface.The research provides a new experimental method for quantitative study on the fracture characteristics of various materials under different breakage conditions.
基金support from the Natural Sciences and Engineering Research Council(NSERC) of Canada
文摘All existing proton exchange membrane （PEM） fuel cell gas flow fields have been designed on the basis of single-phase gas flow distribution. The presence of liquid water in the flow causes non-uniform gas distribution, leading to poor cell performance. This paper demonstrates that a gas flow restrictor/distributor, as is commonly used in two-phase flow to stabilize multiphase transport lines and multiphase reactors, can improve the gas flow distribution by significantly reducing gas real-distribution caused by either non-uniform water formation in parallel flow channels or flow instability associated with negative-slope pressure drop characteristic of two-phase horizontal flow systems.
