In fields such as science and engineering, virtual environment is commonly used to provide replacements for practical hands-on laboratories. Sometimes, these environments take the form of a remote interface to the phy...In fields such as science and engineering, virtual environment is commonly used to provide replacements for practical hands-on laboratories. Sometimes, these environments take the form of a remote interface to the physical laboratory apparatus and at other times, in the form of a complete software implementation that simulates the laboratory apparatus. In this paper, we report on the use of a semi-immersive 3D mobile Augmented Reality (mAR) interface and limited simulations as a replacement for practical hands-on laboratories in science and engineering. The 3D-mAR based interfaces implementations for three different experiments (from micro-electronics, power and communications engineering) are presented;the discovered limitations are discussed along with the results of an evaluation by science and engineering students from two different institutions and plans for future work.展开更多
The analysis of Greenhouse Effect experiments in the public domain indicated that the lab tests were primarily centered around illustrating the mechanics of conventional greenhouses. They used high-energy visible ligh...The analysis of Greenhouse Effect experiments in the public domain indicated that the lab tests were primarily centered around illustrating the mechanics of conventional greenhouses. They used high-energy visible light (such as sunlight), rather than addressing the Greenhouse Effect, which involves low-energy infrared radiation emitted by the Earth’s surface. Studies with argon, a non-greenhouse gas with similar density to CO2, showed thermal heat transfer as the dominant factor in the temperature profiles, with radiation absorption being undetected. The same conclusion was drawn by another study, which measured infrared back radiation. Experiments using exaggerated CO2 concentrations inadvertently illustrated the principle of the Popper Falsification Test by disproving the Greenhouse Effect applicable to CO2 within the troposphere. A straightforward kitchen test showed that a microwave oven cannot be used as a model for the Greenhouse Effect.展开更多
Steel mesh is used as a passive skin confinement medium to supplement the active support provided by rock bolts for roof and rib control in underground coal mines. Thin spray-on liners(TSL) are believed to have the po...Steel mesh is used as a passive skin confinement medium to supplement the active support provided by rock bolts for roof and rib control in underground coal mines. Thin spray-on liners(TSL) are believed to have the potential to take the place of steel mesh as the skin confinement medium in underground mines.To confirm this belief, large scale laboratory experiments were conducted to compare the behaviour of welded steel mesh and a TSL, when used in conjunction with rock bolts, in reinforcing strata with weak bedding planes and strata prone to guttering, two common rock conditions which exist in coal mines. It was found that while the peak load taken by the simulated rock mass with weak bedding planes acting as the control sample(no skin confinement) was 2494 kN, the corresponding value of the sample with 5 mm thick TSL reinforcement reached 2856 kN. The peak load of the steel mesh reinforced sample was only2321 kN, but this was attributed to the fact that one of the rock bolts broke during the test. The TSL reinforced sample had a similar post-yield behaviour as the steel mesh reinforced one. The results of the large scale guttering test indicated that a TSL is better than steel mesh in restricting rock movement and thus inhibiting the formation of gutters in the roof.展开更多
Laboratory experiments were conducted in a wave flume on internal solitary wave （ISW） of depression and elevation types propagating over a submarine ridge in semicircular/triangular shape. Tests were arranged in ser...Laboratory experiments were conducted in a wave flume on internal solitary wave （ISW） of depression and elevation types propagating over a submarine ridge in semicircular/triangular shape. Tests were arranged in series for combinations of submarine ridges of different heights and ISW of different amplitudes. The resuhant wave motions were found differing from thee of surface gravity waves. In deeper water, where an ISW of depression-type prevailed, the process of wave breaking displayed downward motion with continuous eddy on the front face of the ridge followed by upward motion towards the apex of the obstacle. Experimental results also suggested that blockage parameter ξ could be applied to classify various degrees of ISW-ridge interaction, i.e., ξ 〈 0.5 for weak interaction, 0.5 〈 ξ 〈 0.7 for moderate interaction, and 0.7 〈 ξ for wave breaking.展开更多
Abstract Accurate simulation of seismic wave propaga- tion in complex geological structures is of particular interest nowadays. However conventional methods may fail to simulate realistic wavefields in environments wi...Abstract Accurate simulation of seismic wave propaga- tion in complex geological structures is of particular interest nowadays. However conventional methods may fail to simulate realistic wavefields in environments with great and rapid structural changes, due for instance to the presence of shadow zones, diffractions and/or edge effects. Different methods, developed to improve seismic model- ing, are typically tested on synthetic configurations against analytical solutions for simple canonical problems or ref- erence methods, or via direct comparison with real data acquired in situ. Such approaches have limitations,especially if the propagation occurs in a complex envi- ronment with strong-contrast reflectors and surface irreg- ularities, as it can be difficult to determine the method which gives the best approximation of the ＂real＂ solution, or to interpret the results obtained without an a priori knowledge of the geologic environment. An alternative approach for seismics consists in comparing the synthetic data with high-quality data collected in laboratory experi- ments under controlled conditions for a known configuration. In contrast with numerical experiments, laboratory data possess many of the characteristics of field data, as real waves propagate through models with no numerical approximations. We thus present a comparison of laboratory-scaled measurements of 3D zero-offset wave reflection of broadband pulses from a strong topographic environment immersed in a water tank with numerical data simulated by means of a spectral-element method and a discretized Kirchhoff integral method. The results indicate a good quantitative fit in terms of time arrivals and acceptable fit in amplitudes for all datasets.展开更多
Compared with the middle-shallow shale gas reservoirs,deep shale formation often reveals lower fracture complexity,smaller effective stimulated volumes,lower conductivity,and faster declined when the same injection mo...Compared with the middle-shallow shale gas reservoirs,deep shale formation often reveals lower fracture complexity,smaller effective stimulated volumes,lower conductivity,and faster declined when the same injection model and technical parameters were used.Therefore,it is necessary to research a special injection model for the deep shale formation.In this paper,a series of laboratory stimulated experiments were carried to analyze the injection method on hydraulic fracturing initiation and propagation in the deep shale formation.The outcrop shale of Longmaxi formation in Sichuan Basin was selected and three different injection methods(constant,stepped-rise and cyclic progressive uplift pump rate)were used in these experiments.The test results showed that the stepped-rise pump rate is conductive to opening the pre-existing natural fracture and bedding planes,the fracture complexity of this injection method is the highest.Meanwhile,the fracturing pressure and total injection volume are the lowest.In contrast,the cyclic-uplift injection method can only form a transverse fracture,and the fracturing pressure is the highest.The research results have an important theoretical guiding value for deep shale hydraulic fracturing operation.展开更多
In order to improve our understanding of rock fracture and fault instability driven by high-pressure fluid sources, the authors carried out rock fracture tests using granite under a confining pressure of 80 MPa with f...In order to improve our understanding of rock fracture and fault instability driven by high-pressure fluid sources, the authors carried out rock fracture tests using granite under a confining pressure of 80 MPa with fluid injection in the laboratory. Furthermore, we tested a number of numerical models using the FLAC;modeling software to find the best model to represent the experimental results. The high-speed multichannel acoustic emission（AE） waveform recording system used in this study made it possible to examine the total fracture process through detailed monitoring of AE hypocenters and seismic velocity.The experimental results show that injecting high-pressure oil into the rock sample can induce AE activity at very low stress levels and can dramatically reduce the strength of the rock. The results of the numerical simulations show that major experimental results, including the strength, the temporal and spatial patterns of the AE events, and the role of the fluid can be represented fairly well by a model involving（1） randomly distributed defect elements to model pre-existing cracks,（2） random modification of rock properties to represent inhomogeneity introduced by different mineral grains, and（3）macroscopic inhomogeneity. Our study, which incorporates laboratory experiments and numerical simulations, indicates that such an approach is helpful in finding a better model not only for simulating experimental results but also for upscaling purposes.展开更多
A novel expandable conductor was designed and applied in deep-water drilling to improve the vertical and lateral bearing capacity with a significant reduction of conductor jetting depth and soaking time. The vertical ...A novel expandable conductor was designed and applied in deep-water drilling to improve the vertical and lateral bearing capacity with a significant reduction of conductor jetting depth and soaking time. The vertical and lateral bearing capability of expandable conductors was depicted based on the ultimate subgrade reaction method and pile foundation bearing theory. The load-bearing characteristics of a laboratory-scale expandable conductor were analyzed through laboratory experiments. The serial simulation experiments are accomplished to study the bearing characteristics(vertical ultimate bearing capacity, lateral soil pressure, and lateral displacement) during the conductor soaking process. The laboratory experimental results show that the larger the length and thickness of expandable materials are,the higher the bearing capacity of the wellhead will be. During the conductor soaking process, the soil pressure around the three expandable conductors increases faster, strings representing a stronger squeezing effect and resulting in higher vertical bearing capacity. Furthermore, the lateral displacement of novel expandable conductor is smaller than that of the conventional conductor. All the advantages mentioned above contributed to the reduction of conductor’s jetting depth and soaking time. Lastly, the application workflow of a novel expandable deep-water drilling conductor was established and the autonomous expandable conductor was successfully applied in the South China Sea with a significant reduction of conductor’s jetting depth and soaking time. According to the soil properties and designed installation depth of the surface conductor, the arrangement of expandable materials should be designed reasonably to meet the safety condition and reduce the construction cost of the subsea wellhead.展开更多
Geophysical fluid dynamics(GFD)is an interdisciplinary field that studies the large-scale motion of fluids in the natural world.With a wide range of applications such as weather forecasts and climate prediction,GFD em...Geophysical fluid dynamics(GFD)is an interdisciplinary field that studies the large-scale motion of fluids in the natural world.With a wide range of applications such as weather forecasts and climate prediction,GFD employs various research approaches including in-situ observations,satellite measurements,numerical simulations,theoretical analysis,artificial intelligence,and physical model experiments in laboratory.Among these approaches,rotating tank experiments provide a valuable tool for simulating naturally-occurring fluid motions in laboratories.With proportional scaling and proper techniques,scientists can reproduce multi-scale physical processes of stratified fluids in the rotation system,which allows for the simulation of essential characteristics of fluid motions in the atmosphere and oceans.In this review,rotating tanks of various scales in the world are introduced,as these tanks have been actively used to explore fundamental scientific questions in ocean and atmosphere dynamics.To illustrate the GFD experiments,three representative cases are presented to demonstrate the frontier achievements in the the GFD study by using rotating tank experiments:mesoscale eddies in the ocean,convection processes,and plume dynamics.Detailed references for the experimental procedures are provided.Future studies are encouraged to further explore the utilization of rotating tanks with improvements in experimental design and integration of other research methods.This is a promising direction of GFD to help enhance our understanding of the complex nature of fluid motions in the natural world and to address the challenges posed by global environmental changes.展开更多
Shales are considered to be sealing units for geological carbon storage and suitable host rocks for nuclear waste repositories due to their low permeability.However,the presence of fractures within these formations ca...Shales are considered to be sealing units for geological carbon storage and suitable host rocks for nuclear waste repositories due to their low permeability.However,the presence of fractures within these formations can significantly alter their flow,transport,and deformation behavior,which is central to the safe implementation of underground storage projects.Fractures not only increase the overall permeability of the rock but also contribute to its anisotropic behavior.This study focuses on characterizing the hydro-mechanical response of a natural fracture to aqueous fluid injection within a shaly specimen of Opalinus Clay.Laboratory experiments were performed to measure the mechanical and flow properties of intact and fractured rock specimens.Subsequently,a three-dimensional(3D)numerical model of water injection into the fractured specimen was developed.This model explicitly accounts for fracture geometry with strain-dependent aperture changes based on the cubic law assumption.Experimental measurements indicate that the fractured shale exhibits permeability up to two orders of magnitude higher than that of the intact counterpart.However,the simulations reveal that fracture permeability locally spans up to eight orders of magnitude.This significant change in permeability affects fluid flow within the rock specimen.The numerical model best reproduces the experimental results for a normal stiffness of the natural fracture of 18.7 MPa/mm at effective mean stresses below 15 MPa,and of 187.2 MPa/mm at higher confinements.This outcome highlights the critical importance of defining the hydro-mechanical parameters of fractures under realistic effective stress conditions with far-reaching implications for secure underground storage.展开更多
Lost circulation critically jeopardizes drilling safety and efficiency,and remains an unresolved challenge in oil and gas engineering.In this paper,by utilizing the self-developed dynamic plugging apparatus and synthe...Lost circulation critically jeopardizes drilling safety and efficiency,and remains an unresolved challenge in oil and gas engineering.In this paper,by utilizing the self-developed dynamic plugging apparatus and synthetic cores containing large-scale fractures,experimental research on the circulation plugging of different materials was conducted.Based on the D90 rule and fracture mechanical aperture model,we analyze the location of plugging layer under dynamic plugging mechanism.By setting different parameters of fracture width and injection pressure,the laws of cyclic plugging time,pressure bearing capacity and plugging layers formation were investigated.The results show that the comprehensive analysis of particle size and fracture aperture provides an accurate judgment of the entrance-plugging phenomenon.The bridging of solid materials in the leakage channel is a gradual process,and the formation of a stable plug requires 2–3 plug-leakage cycles.The first and second cyclic plugging time was positively correlated with the fracture width.Different scales of fractures were successfully plugged with the bearing pressure greater than 6 MPa,but there were significant differences in the composition of the plugging layer.The experimental results can effectively prove that the utilized plugging agent is effective and provides an effective reference for dynamic plugging operation.展开更多
In a Nature Physics report published in late September 2024[1],a team of scientists and engineers at Sandia National Laboratories(Albuquerque,NM,USA)described the results of a laboratory experiment showing that a nucl...In a Nature Physics report published in late September 2024[1],a team of scientists and engineers at Sandia National Laboratories(Albuquerque,NM,USA)described the results of a laboratory experiment showing that a nuclear blast could create a burst of X-rays powerful enough to change the path of a large asteroid that might one day be on a collision course with Earth.展开更多
We report the observation of Zeeman splitting in multiple spectral lines emitted by a laser-produced,magnetized plasma(1–3×10^(18)cm^(-3),1–15 eV)in the context of a laboratory astrophysics experiment under a c...We report the observation of Zeeman splitting in multiple spectral lines emitted by a laser-produced,magnetized plasma(1–3×10^(18)cm^(-3),1–15 eV)in the context of a laboratory astrophysics experiment under a controlled magneticfield up to 20T.Nitrogen lines(NII)in the visible range were used to diagnose the magneticfield and plasma conditions.This was performed by coupling our data with(563–574 nm)the Stark–Zeeman line-shape code PPPB.The excellent agreement between experiment and simulations paves the way for a non-intrusive experimental platform to get time-resolved measurements of the local magneticfield in laboratory plasmas.展开更多
Sulfate rocks and organic sulfur from sedimentary organic matter are conventionally assumed as the original sulfur sources for hydrogen sulfide （H2S） in oil and gas reservoirs. However, a few recent experiments prel...Sulfate rocks and organic sulfur from sedimentary organic matter are conventionally assumed as the original sulfur sources for hydrogen sulfide （H2S） in oil and gas reservoirs. However, a few recent experiments preliminarily indicate that the association of pyrite and hydrocarbons may also have implications for H2S generation, in which water effects and natural controls on the evolution of pyrite sulfur into OSCs and H2S have not been evaluated. In this study, laboratory experiments were conducted from 200 to 450°C to investigate chemical interactions between pyrite and hydrocarbons under hydrothermal conditions. Based on the experimental results, preliminary mechanism and geochemical implications were tentatively discussed. Results of the experiments showed that decomposition of pyrite produced H2S and thiophenes at as low as 330°C in the presence of water and n-pentane. High concentrations of H2S were generated above 450°C under closed pyrolysis conditions no matter whether there is water in the designed experiments. However, much more organic sulfur compounds （OSCs） were formed in the hydrous pyrolysis than in anhydrous pyrolysis. Generally, most of sulfur liberated from pyrite at elevated temperatures was converted to H2S. Water was beneficial to breakdown of pyrite and to decomposition of alkanes into olefins but not essential to formation of large amounts of H2S, given the main hydrogen source derived from hydrocarbons. In addition, cracking of pyrite in the presence of 1-octene under hydrous conditions was found to proceed at 200°C, producing thiols and alkyl sulfides. Unsaturated hydrocarbons would be more reactive intermediates involved in the breakdown of pyrite than alkanes. The geochemistry of OSCs is actually controlled by various geochemical factors such as thermal maturity and the carbon chain length of the alkanes. This study indicates that the scale of H2S gas generated in deep buried carbonate reservoirs via interactions between pyrite and natural gas should be much smaller than that of thermochemical sulfate reduction （TSR） due to the scarcity of pyrite in carbonate reservoirs and the limited amount of long-chained hydrocarbons in natural gas. Nevertheless, in some cases, OSCs and/or low contents of H2S found in deep buried reservoirs may be associated with the deposited pyrite-bearing rock and organic matters （hydrocarbons）, which still needs further investigation.展开更多
Discrete fracture models are used for investigating precise processes of groundwater flow in fractured rocks,while a disc-shaped parallel-plates model for a single fracture is more reasonable and efficient for computa...Discrete fracture models are used for investigating precise processes of groundwater flow in fractured rocks,while a disc-shaped parallel-plates model for a single fracture is more reasonable and efficient for computational treatments.The flow velocity has a large spatial differentiation which is more likely to produce non-linear flow and additional head losses on and nearby intersections in such shaped fractures,therefore it is necessary to understand and quantify them.In this study,both laboratory experiments and numerical simulations were performed to investigate the total head loss on and nearby the intersections as well as the local head loss exactly on the intersections,which were not usually paid sufficient attention or even ignored.The investigation results show that these two losses account for 29.17%-84.97%and 0-73.57%of the entire total head loss in a fracture,respectively.As a result,they should be necessarily considered for groundwater modeling in fractured rocks.Furthermore,both head losses become larger when aperture and flow rate increase and intersection length decreases.Particularly,the ratios of these two head losses to the entire total head loss in a fracture could be well statistically explained by power regression equations with variables of aperture,intersection length,and flow rates,both of which achieved high coefficients of determination.It could be feasible through this type of study to provide a way on how to adjust the groundwater head from those obtained by numerical simulations based on the traditional linear flow model.Finally,it is practicable and effective to implement the investigation approach combining laboratory experiments with numerical simulations for quantifying the head losses on and nearby the intersections between disc-shaped fractures.展开更多
An experimental study is presented on the non-Gaussian statistics of random unidirectional laboratory wave fields described by JONSWAP spectra.Relationships between statistical parameters indicative of the occurrence ...An experimental study is presented on the non-Gaussian statistics of random unidirectional laboratory wave fields described by JONSWAP spectra.Relationships between statistical parameters indicative of the occurrence of largeamplitude waves are discussed in the context of the initial steepness of the waves combined with the effect of spectral peakedness.The spatial evolution of the relevant statistical and spectral parameters and features is also considered.It is demonstrated that over the distance the spectra exhibit features typical for developing nonlinear instabilities,such as spectral broadening and downshift of the peak,along with lowering of the high-frequency tail and decrease of the peak magnitude.The wave fields clearly show an increase of third-order nonlinearity with the distance,which can be significant,depending on the input wave environment.The steeper initial conditions,however,while favouring the occurrence of extremely large waves,also increase the chances of wave breaking and loss of energy due to dissipation,which results in lower extreme crests and wave heights.The applied Miche-Stokes-type criteria do confirm that some of the wave extremes exceed the limiting individual steepness.Eventually,this result agrees with the observation that the largest number of abnormal waves is recorded in sea states with moderate steepness.展开更多
With the rapid decline of Arctic sea ice, the freshwater produced by melting of summer sea ice makes the depth of the halocline under ice become shallower. This has an impact on the drift of sea ice because internal w...With the rapid decline of Arctic sea ice, the freshwater produced by melting of summer sea ice makes the depth of the halocline under ice become shallower. This has an impact on the drift of sea ice because internal waves may be generated at the interface of the halocline by disturbance from the draft of an ice floe or ridge keel. A laboratory experimental study was carried out to investigate the interactions between an ice ridge and stratified fluid using the method of Particle Image Velocimetry （PIV）. The drift velocity of an ice ridge （U） and the draft of the ridge keel （D） were altered in different experimental cases, and the velocity field in the stratified fluid was then measured by PIV. The results reveal that an obvious vortex exists in the wake field of the ridge keel, and the center of the vortex moves away from the ice ridge with increasing D. Internal waves at the interface of the stratified fluid were observed during the drift of the ice ridge, and the wave height shows a positive correlation with U and D. This study demonstrates that ice ridges could introduce internal waves at the interface of a stratified fluid and thus affect the oceanic drag coefficient and ice drift. It supports improved parameterization of the ice drag coefficients.展开更多
This paper describes a dual-stroke acting hydraulic power take-off （PTO） system employed in the wave energy converter （WEC） with an inverse pendulum. The hydraulic PTO converts slow irregular reciprocating wave mo...This paper describes a dual-stroke acting hydraulic power take-off （PTO） system employed in the wave energy converter （WEC） with an inverse pendulum. The hydraulic PTO converts slow irregular reciprocating wave motions to relatively smooth, fast rotation of an electrical generator. The design of the hydraulic PTO system and its control are critical to maximize the generated power. A time domain simulation study and the laboratory experiment of the full-scale beach test are presented. The results of the simulation and laboratory experiments including their comparison at full-scale are also presented, which have validated the rationality of the design and the reliability of some key components of the prototype of the WEC with an inverse pendulum with the dual-stroke acting hydraulic PTO system.展开更多
Soft rock control is a big challenge in underground engineering.As for this problem,a high-strength support technique of confined concrete(CC)arches is proposed and studied in this paper.Based on full-scale mechanical...Soft rock control is a big challenge in underground engineering.As for this problem,a high-strength support technique of confined concrete(CC)arches is proposed and studied in this paper.Based on full-scale mechanical test system of arch,research is made on the failure mechanism and mechanical properties of CC arch.Then,a mechanical calculation model of circular section is established for the arches with arbitrary section and unequal rigidity;a calculation formula is deduced for the internal force of the arch;an analysis is made on the influence of different factors on the internal force of the arch;and a calculation formula is got for the bearing capacity of CC arch through the strength criterion of bearing capacity.With numerical calculation and laboratory experiment,the ultimate bearing capacity and internal force distribution is analyzed for CC arches.The research results show that:1)CC arch is 2.31 times higher in strength than the U-shaped steel arch and has better stability;2)The key damage position of the arch is the two sides;3)Theoretical analysis,numerical calculation and laboratory experiment have good consistency in the internal force distribution,bearing capacity,and deformation and failure modes of the arch.All of that verifies the correctness of the theoretical calculation.Based on the above results,a field experiment is carried out in Liangjia Mine.Compared with the U-shaped steel arch support,CC arch support is more effective in surrounding rock deformation control.The research results can provide a basis for the design of CC arch support in underground engineering.展开更多
Highway frost heave and thawing settlement caused by water migration towards the freezing front and ice lens development is widespread in the alpine meadow area of the southeast QinghaiTibet Plateau(QTP). A laboratory...Highway frost heave and thawing settlement caused by water migration towards the freezing front and ice lens development is widespread in the alpine meadow area of the southeast QinghaiTibet Plateau(QTP). A laboratory experiment on a highway reconstruction and expansion project in the QTP was carried out in this work to analyze the effects of fine particle content, initial water content, and the number of freeze-thaw cycles(FTCs) on frost depth, temperature gradient(Grad T), total water intake, and water intake flux. Based on the results of the laboratory experiment, a modified model of migration potential related to fine particle content, freeze-thaw history, and freezing time was established. The results show that, with the increase of fine particle content, the frost depth of soil decreases, the curve of total water intake over time is transformed from an Sshape to an arch, and the curve of water intake flux over time is transformed from a peak shape to descending shape. The variation trend of migration potential with freezing time and the freeze-thaw history is the same as that of water intake flux with freezing time and freeze-thaw history. The variation trend of soil intake flux can be used as a reference to determine the variation trend of soil migration potential. This study provides a reference for the design and construction of highway subgrade in the alpine meadow area of the QTP.展开更多
文摘In fields such as science and engineering, virtual environment is commonly used to provide replacements for practical hands-on laboratories. Sometimes, these environments take the form of a remote interface to the physical laboratory apparatus and at other times, in the form of a complete software implementation that simulates the laboratory apparatus. In this paper, we report on the use of a semi-immersive 3D mobile Augmented Reality (mAR) interface and limited simulations as a replacement for practical hands-on laboratories in science and engineering. The 3D-mAR based interfaces implementations for three different experiments (from micro-electronics, power and communications engineering) are presented;the discovered limitations are discussed along with the results of an evaluation by science and engineering students from two different institutions and plans for future work.
文摘The analysis of Greenhouse Effect experiments in the public domain indicated that the lab tests were primarily centered around illustrating the mechanics of conventional greenhouses. They used high-energy visible light (such as sunlight), rather than addressing the Greenhouse Effect, which involves low-energy infrared radiation emitted by the Earth’s surface. Studies with argon, a non-greenhouse gas with similar density to CO2, showed thermal heat transfer as the dominant factor in the temperature profiles, with radiation absorption being undetected. The same conclusion was drawn by another study, which measured infrared back radiation. Experiments using exaggerated CO2 concentrations inadvertently illustrated the principle of the Popper Falsification Test by disproving the Greenhouse Effect applicable to CO2 within the troposphere. A straightforward kitchen test showed that a microwave oven cannot be used as a model for the Greenhouse Effect.
文摘Steel mesh is used as a passive skin confinement medium to supplement the active support provided by rock bolts for roof and rib control in underground coal mines. Thin spray-on liners(TSL) are believed to have the potential to take the place of steel mesh as the skin confinement medium in underground mines.To confirm this belief, large scale laboratory experiments were conducted to compare the behaviour of welded steel mesh and a TSL, when used in conjunction with rock bolts, in reinforcing strata with weak bedding planes and strata prone to guttering, two common rock conditions which exist in coal mines. It was found that while the peak load taken by the simulated rock mass with weak bedding planes acting as the control sample(no skin confinement) was 2494 kN, the corresponding value of the sample with 5 mm thick TSL reinforcement reached 2856 kN. The peak load of the steel mesh reinforced sample was only2321 kN, but this was attributed to the fact that one of the rock bolts broke during the test. The TSL reinforced sample had a similar post-yield behaviour as the steel mesh reinforced one. The results of the large scale guttering test indicated that a TSL is better than steel mesh in restricting rock movement and thus inhibiting the formation of gutters in the roof.
基金The work was supported bythe National Science Council ,Taiwan,China (Grant No. NSC93-2611-M-110-001)
文摘Laboratory experiments were conducted in a wave flume on internal solitary wave （ISW） of depression and elevation types propagating over a submarine ridge in semicircular/triangular shape. Tests were arranged in series for combinations of submarine ridges of different heights and ISW of different amplitudes. The resuhant wave motions were found differing from thee of surface gravity waves. In deeper water, where an ISW of depression-type prevailed, the process of wave breaking displayed downward motion with continuous eddy on the front face of the ridge followed by upward motion towards the apex of the obstacle. Experimental results also suggested that blockage parameter ξ could be applied to classify various degrees of ISW-ridge interaction, i.e., ξ 〈 0.5 for weak interaction, 0.5 〈 ξ 〈 0.7 for moderate interaction, and 0.7 〈 ξ for wave breaking.
基金the INSIS Institute of the French CNRS,Aix-Marseille Universitythe Carnot Star Institute,the VISTA Projectthe Norwegian Research Council through the ROSE Project for financial support
文摘Abstract Accurate simulation of seismic wave propaga- tion in complex geological structures is of particular interest nowadays. However conventional methods may fail to simulate realistic wavefields in environments with great and rapid structural changes, due for instance to the presence of shadow zones, diffractions and/or edge effects. Different methods, developed to improve seismic model- ing, are typically tested on synthetic configurations against analytical solutions for simple canonical problems or ref- erence methods, or via direct comparison with real data acquired in situ. Such approaches have limitations,especially if the propagation occurs in a complex envi- ronment with strong-contrast reflectors and surface irreg- ularities, as it can be difficult to determine the method which gives the best approximation of the ＂real＂ solution, or to interpret the results obtained without an a priori knowledge of the geologic environment. An alternative approach for seismics consists in comparing the synthetic data with high-quality data collected in laboratory experi- ments under controlled conditions for a known configuration. In contrast with numerical experiments, laboratory data possess many of the characteristics of field data, as real waves propagate through models with no numerical approximations. We thus present a comparison of laboratory-scaled measurements of 3D zero-offset wave reflection of broadband pulses from a strong topographic environment immersed in a water tank with numerical data simulated by means of a spectral-element method and a discretized Kirchhoff integral method. The results indicate a good quantitative fit in terms of time arrivals and acceptable fit in amplitudes for all datasets.
基金funded by the National Science and Technology Major Project of China,2016ZX05060-004,2017ZX05036-003the National Natural Science Foundation of China,51574218Strategic Priority Research Program of the Chinese Academy of Sciences,grant number XDB10040200。
文摘Compared with the middle-shallow shale gas reservoirs,deep shale formation often reveals lower fracture complexity,smaller effective stimulated volumes,lower conductivity,and faster declined when the same injection model and technical parameters were used.Therefore,it is necessary to research a special injection model for the deep shale formation.In this paper,a series of laboratory stimulated experiments were carried to analyze the injection method on hydraulic fracturing initiation and propagation in the deep shale formation.The outcrop shale of Longmaxi formation in Sichuan Basin was selected and three different injection methods(constant,stepped-rise and cyclic progressive uplift pump rate)were used in these experiments.The test results showed that the stepped-rise pump rate is conductive to opening the pre-existing natural fracture and bedding planes,the fracture complexity of this injection method is the highest.Meanwhile,the fracturing pressure and total injection volume are the lowest.In contrast,the cyclic-uplift injection method can only form a transverse fracture,and the fracturing pressure is the highest.The research results have an important theoretical guiding value for deep shale hydraulic fracturing operation.
基金supported by State Key Laboratory of Earthquake Dynamics,China
文摘In order to improve our understanding of rock fracture and fault instability driven by high-pressure fluid sources, the authors carried out rock fracture tests using granite under a confining pressure of 80 MPa with fluid injection in the laboratory. Furthermore, we tested a number of numerical models using the FLAC;modeling software to find the best model to represent the experimental results. The high-speed multichannel acoustic emission（AE） waveform recording system used in this study made it possible to examine the total fracture process through detailed monitoring of AE hypocenters and seismic velocity.The experimental results show that injecting high-pressure oil into the rock sample can induce AE activity at very low stress levels and can dramatically reduce the strength of the rock. The results of the numerical simulations show that major experimental results, including the strength, the temporal and spatial patterns of the AE events, and the role of the fluid can be represented fairly well by a model involving（1） randomly distributed defect elements to model pre-existing cracks,（2） random modification of rock properties to represent inhomogeneity introduced by different mineral grains, and（3）macroscopic inhomogeneity. Our study, which incorporates laboratory experiments and numerical simulations, indicates that such an approach is helpful in finding a better model not only for simulating experimental results but also for upscaling purposes.
基金financially supported by the National Natural Science Foundation of China (Grant Nos.51434009 and 51221003)。
文摘A novel expandable conductor was designed and applied in deep-water drilling to improve the vertical and lateral bearing capacity with a significant reduction of conductor jetting depth and soaking time. The vertical and lateral bearing capability of expandable conductors was depicted based on the ultimate subgrade reaction method and pile foundation bearing theory. The load-bearing characteristics of a laboratory-scale expandable conductor were analyzed through laboratory experiments. The serial simulation experiments are accomplished to study the bearing characteristics(vertical ultimate bearing capacity, lateral soil pressure, and lateral displacement) during the conductor soaking process. The laboratory experimental results show that the larger the length and thickness of expandable materials are,the higher the bearing capacity of the wellhead will be. During the conductor soaking process, the soil pressure around the three expandable conductors increases faster, strings representing a stronger squeezing effect and resulting in higher vertical bearing capacity. Furthermore, the lateral displacement of novel expandable conductor is smaller than that of the conventional conductor. All the advantages mentioned above contributed to the reduction of conductor’s jetting depth and soaking time. Lastly, the application workflow of a novel expandable deep-water drilling conductor was established and the autonomous expandable conductor was successfully applied in the South China Sea with a significant reduction of conductor’s jetting depth and soaking time. According to the soil properties and designed installation depth of the surface conductor, the arrangement of expandable materials should be designed reasonably to meet the safety condition and reduce the construction cost of the subsea wellhead.
基金Supported by the National Key Research and Development Program of China(Nos.2017YFA0604100,2016YFC1402004,2017YFC1404200)the Program for Innovation Research and Entrepreneurship Team in Jiangsu Provincethe National Natural Science Foundation of China(Nos.41476022,41490643)。
文摘Geophysical fluid dynamics(GFD)is an interdisciplinary field that studies the large-scale motion of fluids in the natural world.With a wide range of applications such as weather forecasts and climate prediction,GFD employs various research approaches including in-situ observations,satellite measurements,numerical simulations,theoretical analysis,artificial intelligence,and physical model experiments in laboratory.Among these approaches,rotating tank experiments provide a valuable tool for simulating naturally-occurring fluid motions in laboratories.With proportional scaling and proper techniques,scientists can reproduce multi-scale physical processes of stratified fluids in the rotation system,which allows for the simulation of essential characteristics of fluid motions in the atmosphere and oceans.In this review,rotating tanks of various scales in the world are introduced,as these tanks have been actively used to explore fundamental scientific questions in ocean and atmosphere dynamics.To illustrate the GFD experiments,three representative cases are presented to demonstrate the frontier achievements in the the GFD study by using rotating tank experiments:mesoscale eddies in the ocean,convection processes,and plume dynamics.Detailed references for the experimental procedures are provided.Future studies are encouraged to further explore the utilization of rotating tanks with improvements in experimental design and integration of other research methods.This is a promising direction of GFD to help enhance our understanding of the complex nature of fluid motions in the natural world and to address the challenges posed by global environmental changes.
基金the funding from the European Research Council(ERC)under the European Union's Horizon 2020 Research and Innovation Program through the Starting Grant GEoREST(www.georest.eu)under Grant agreement No.801809IMEDEA is an accredited“Maria de Maeztu Excellence Unit”(Grant CEX2021-001198+2 种基金funded by MICIU/AEI/10.13039/501100011033)Iman R.Kivi also acknowledges the funding from the Engineering and Physical Sciences Research Council through the UKRI Postdoc Guarantee Award THMC4CCS(Grant No.EP/X026019/1)Hyunbin Kim and Roman Y.Makhnenko are supported by the US National Science Foundation(Grant No.CMMI-2239630).
文摘Shales are considered to be sealing units for geological carbon storage and suitable host rocks for nuclear waste repositories due to their low permeability.However,the presence of fractures within these formations can significantly alter their flow,transport,and deformation behavior,which is central to the safe implementation of underground storage projects.Fractures not only increase the overall permeability of the rock but also contribute to its anisotropic behavior.This study focuses on characterizing the hydro-mechanical response of a natural fracture to aqueous fluid injection within a shaly specimen of Opalinus Clay.Laboratory experiments were performed to measure the mechanical and flow properties of intact and fractured rock specimens.Subsequently,a three-dimensional(3D)numerical model of water injection into the fractured specimen was developed.This model explicitly accounts for fracture geometry with strain-dependent aperture changes based on the cubic law assumption.Experimental measurements indicate that the fractured shale exhibits permeability up to two orders of magnitude higher than that of the intact counterpart.However,the simulations reveal that fracture permeability locally spans up to eight orders of magnitude.This significant change in permeability affects fluid flow within the rock specimen.The numerical model best reproduces the experimental results for a normal stiffness of the natural fracture of 18.7 MPa/mm at effective mean stresses below 15 MPa,and of 187.2 MPa/mm at higher confinements.This outcome highlights the critical importance of defining the hydro-mechanical parameters of fractures under realistic effective stress conditions with far-reaching implications for secure underground storage.
基金financially supported by National Natural Science Foundation of China(No.52422402)。
文摘Lost circulation critically jeopardizes drilling safety and efficiency,and remains an unresolved challenge in oil and gas engineering.In this paper,by utilizing the self-developed dynamic plugging apparatus and synthetic cores containing large-scale fractures,experimental research on the circulation plugging of different materials was conducted.Based on the D90 rule and fracture mechanical aperture model,we analyze the location of plugging layer under dynamic plugging mechanism.By setting different parameters of fracture width and injection pressure,the laws of cyclic plugging time,pressure bearing capacity and plugging layers formation were investigated.The results show that the comprehensive analysis of particle size and fracture aperture provides an accurate judgment of the entrance-plugging phenomenon.The bridging of solid materials in the leakage channel is a gradual process,and the formation of a stable plug requires 2–3 plug-leakage cycles.The first and second cyclic plugging time was positively correlated with the fracture width.Different scales of fractures were successfully plugged with the bearing pressure greater than 6 MPa,but there were significant differences in the composition of the plugging layer.The experimental results can effectively prove that the utilized plugging agent is effective and provides an effective reference for dynamic plugging operation.
文摘In a Nature Physics report published in late September 2024[1],a team of scientists and engineers at Sandia National Laboratories(Albuquerque,NM,USA)described the results of a laboratory experiment showing that a nuclear blast could create a burst of X-rays powerful enough to change the path of a large asteroid that might one day be on a collision course with Earth.
基金supported by grants managed by l’Agence Nationale de la Recherche under the Investissements d’Avenir programs Grant Nos. ANR-18-EURE-0014, ANR-10-LABX-0039-PALM, and ANR-22-CE30-0044supported by grants from Japan Society for the Promotion of Science (JSPS) KAKENHI (Grant No. 23K20038)+2 种基金JSPS Core-to-Core program (Grant No. JPJSCCA20230003)carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200-EUROfusion)operated within the framework of the Enabling Research Project No. AWP24-ENR-IFE.02.CEA-01 “Magnetized ICF”
文摘We report the observation of Zeeman splitting in multiple spectral lines emitted by a laser-produced,magnetized plasma(1–3×10^(18)cm^(-3),1–15 eV)in the context of a laboratory astrophysics experiment under a controlled magneticfield up to 20T.Nitrogen lines(NII)in the visible range were used to diagnose the magneticfield and plasma conditions.This was performed by coupling our data with(563–574 nm)the Stark–Zeeman line-shape code PPPB.The excellent agreement between experiment and simulations paves the way for a non-intrusive experimental platform to get time-resolved measurements of the local magneticfield in laboratory plasmas.
基金the National Natural Science Foundations of China(No.41472095 and No.40902034)the Foundation of State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing(No.PRP/open-1508)PetroChina Innovation Foundation(No.2012D-5006-0104)
文摘Sulfate rocks and organic sulfur from sedimentary organic matter are conventionally assumed as the original sulfur sources for hydrogen sulfide （H2S） in oil and gas reservoirs. However, a few recent experiments preliminarily indicate that the association of pyrite and hydrocarbons may also have implications for H2S generation, in which water effects and natural controls on the evolution of pyrite sulfur into OSCs and H2S have not been evaluated. In this study, laboratory experiments were conducted from 200 to 450°C to investigate chemical interactions between pyrite and hydrocarbons under hydrothermal conditions. Based on the experimental results, preliminary mechanism and geochemical implications were tentatively discussed. Results of the experiments showed that decomposition of pyrite produced H2S and thiophenes at as low as 330°C in the presence of water and n-pentane. High concentrations of H2S were generated above 450°C under closed pyrolysis conditions no matter whether there is water in the designed experiments. However, much more organic sulfur compounds （OSCs） were formed in the hydrous pyrolysis than in anhydrous pyrolysis. Generally, most of sulfur liberated from pyrite at elevated temperatures was converted to H2S. Water was beneficial to breakdown of pyrite and to decomposition of alkanes into olefins but not essential to formation of large amounts of H2S, given the main hydrogen source derived from hydrocarbons. In addition, cracking of pyrite in the presence of 1-octene under hydrous conditions was found to proceed at 200°C, producing thiols and alkyl sulfides. Unsaturated hydrocarbons would be more reactive intermediates involved in the breakdown of pyrite than alkanes. The geochemistry of OSCs is actually controlled by various geochemical factors such as thermal maturity and the carbon chain length of the alkanes. This study indicates that the scale of H2S gas generated in deep buried carbonate reservoirs via interactions between pyrite and natural gas should be much smaller than that of thermochemical sulfate reduction （TSR） due to the scarcity of pyrite in carbonate reservoirs and the limited amount of long-chained hydrocarbons in natural gas. Nevertheless, in some cases, OSCs and/or low contents of H2S found in deep buried reservoirs may be associated with the deposited pyrite-bearing rock and organic matters （hydrocarbons）, which still needs further investigation.
基金supported by National Key Research and Development Program of China(No.2020 YFC1807100,No.2019YFC1806205)National Natural Science Foundation of China(No.41572240)。
文摘Discrete fracture models are used for investigating precise processes of groundwater flow in fractured rocks,while a disc-shaped parallel-plates model for a single fracture is more reasonable and efficient for computational treatments.The flow velocity has a large spatial differentiation which is more likely to produce non-linear flow and additional head losses on and nearby intersections in such shaped fractures,therefore it is necessary to understand and quantify them.In this study,both laboratory experiments and numerical simulations were performed to investigate the total head loss on and nearby the intersections as well as the local head loss exactly on the intersections,which were not usually paid sufficient attention or even ignored.The investigation results show that these two losses account for 29.17%-84.97%and 0-73.57%of the entire total head loss in a fracture,respectively.As a result,they should be necessarily considered for groundwater modeling in fractured rocks.Furthermore,both head losses become larger when aperture and flow rate increase and intersection length decreases.Particularly,the ratios of these two head losses to the entire total head loss in a fracture could be well statistically explained by power regression equations with variables of aperture,intersection length,and flow rates,both of which achieved high coefficients of determination.It could be feasible through this type of study to provide a way on how to adjust the groundwater head from those obtained by numerical simulations based on the traditional linear flow model.Finally,it is practicable and effective to implement the investigation approach combining laboratory experiments with numerical simulations for quantifying the head losses on and nearby the intersections between disc-shaped fractures.
基金the Portuguese Foundation for Science and Technology (Fundação para a Ciência e Tecnologia-FCT) under contract UIDB/UIDP/00134/2020The experiments at Lab Oceano were supported by the National Petroleum Agency of Brazil (ANP)
文摘An experimental study is presented on the non-Gaussian statistics of random unidirectional laboratory wave fields described by JONSWAP spectra.Relationships between statistical parameters indicative of the occurrence of largeamplitude waves are discussed in the context of the initial steepness of the waves combined with the effect of spectral peakedness.The spatial evolution of the relevant statistical and spectral parameters and features is also considered.It is demonstrated that over the distance the spectra exhibit features typical for developing nonlinear instabilities,such as spectral broadening and downshift of the peak,along with lowering of the high-frequency tail and decrease of the peak magnitude.The wave fields clearly show an increase of third-order nonlinearity with the distance,which can be significant,depending on the input wave environment.The steeper initial conditions,however,while favouring the occurrence of extremely large waves,also increase the chances of wave breaking and loss of energy due to dissipation,which results in lower extreme crests and wave heights.The applied Miche-Stokes-type criteria do confirm that some of the wave extremes exceed the limiting individual steepness.Eventually,this result agrees with the observation that the largest number of abnormal waves is recorded in sea states with moderate steepness.
基金supported by the National Natural Science Foundation of China(Grant nos.41276191,41306207,41376186)
文摘With the rapid decline of Arctic sea ice, the freshwater produced by melting of summer sea ice makes the depth of the halocline under ice become shallower. This has an impact on the drift of sea ice because internal waves may be generated at the interface of the halocline by disturbance from the draft of an ice floe or ridge keel. A laboratory experimental study was carried out to investigate the interactions between an ice ridge and stratified fluid using the method of Particle Image Velocimetry （PIV）. The drift velocity of an ice ridge （U） and the draft of the ridge keel （D） were altered in different experimental cases, and the velocity field in the stratified fluid was then measured by PIV. The results reveal that an obvious vortex exists in the wake field of the ridge keel, and the center of the vortex moves away from the ice ridge with increasing D. Internal waves at the interface of the stratified fluid were observed during the drift of the ice ridge, and the wave height shows a positive correlation with U and D. This study demonstrates that ice ridges could introduce internal waves at the interface of a stratified fluid and thus affect the oceanic drag coefficient and ice drift. It supports improved parameterization of the ice drag coefficients.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51205346 and 41206074)the National High Technology Research and Development Program of China(863 Program+3 种基金Grant No.2011AA050201)Science Fund for Creative Research Groups of National Natural Science Foundation of China(Grant No.51221004)Zhejiang Provincial Natural Science Foundation of China(Grant No.LY12E05017)Open Foundation of the State Key Laboratory of Fluid Power Transmission and Control(Grant No.GZKF-201311)
文摘This paper describes a dual-stroke acting hydraulic power take-off （PTO） system employed in the wave energy converter （WEC） with an inverse pendulum. The hydraulic PTO converts slow irregular reciprocating wave motions to relatively smooth, fast rotation of an electrical generator. The design of the hydraulic PTO system and its control are critical to maximize the generated power. A time domain simulation study and the laboratory experiment of the full-scale beach test are presented. The results of the simulation and laboratory experiments including their comparison at full-scale are also presented, which have validated the rationality of the design and the reliability of some key components of the prototype of the WEC with an inverse pendulum with the dual-stroke acting hydraulic PTO system.
基金Projects(51674154,51704125,51874188) supported by the National Natural Science Foundation of ChinaProjects(2017T100116,2017T100491,2016M590150,2016M602144) supported by the China Postdoctoral Science Foundation+2 种基金Projects(2017GGX30101,2018GGX109001,ZR2017QEE013) supported by the Natural Science Foundation of Shandong Province,ChinaProject(SKLCRSM18KF012) supported by the State Key Laboratory of Coal Resources and Safe Mining,ChinaProject(2018WLJH76) supported by the Young Scholars Program of Shandong University,China
文摘Soft rock control is a big challenge in underground engineering.As for this problem,a high-strength support technique of confined concrete(CC)arches is proposed and studied in this paper.Based on full-scale mechanical test system of arch,research is made on the failure mechanism and mechanical properties of CC arch.Then,a mechanical calculation model of circular section is established for the arches with arbitrary section and unequal rigidity;a calculation formula is deduced for the internal force of the arch;an analysis is made on the influence of different factors on the internal force of the arch;and a calculation formula is got for the bearing capacity of CC arch through the strength criterion of bearing capacity.With numerical calculation and laboratory experiment,the ultimate bearing capacity and internal force distribution is analyzed for CC arches.The research results show that:1)CC arch is 2.31 times higher in strength than the U-shaped steel arch and has better stability;2)The key damage position of the arch is the two sides;3)Theoretical analysis,numerical calculation and laboratory experiment have good consistency in the internal force distribution,bearing capacity,and deformation and failure modes of the arch.All of that verifies the correctness of the theoretical calculation.Based on the above results,a field experiment is carried out in Liangjia Mine.Compared with the U-shaped steel arch support,CC arch support is more effective in surrounding rock deformation control.The research results can provide a basis for the design of CC arch support in underground engineering.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.310821173701)Natural Science Basic Research Program of Shaanxi(Grant No.2020JQ-379)。
文摘Highway frost heave and thawing settlement caused by water migration towards the freezing front and ice lens development is widespread in the alpine meadow area of the southeast QinghaiTibet Plateau(QTP). A laboratory experiment on a highway reconstruction and expansion project in the QTP was carried out in this work to analyze the effects of fine particle content, initial water content, and the number of freeze-thaw cycles(FTCs) on frost depth, temperature gradient(Grad T), total water intake, and water intake flux. Based on the results of the laboratory experiment, a modified model of migration potential related to fine particle content, freeze-thaw history, and freezing time was established. The results show that, with the increase of fine particle content, the frost depth of soil decreases, the curve of total water intake over time is transformed from an Sshape to an arch, and the curve of water intake flux over time is transformed from a peak shape to descending shape. The variation trend of migration potential with freezing time and the freeze-thaw history is the same as that of water intake flux with freezing time and freeze-thaw history. The variation trend of soil intake flux can be used as a reference to determine the variation trend of soil migration potential. This study provides a reference for the design and construction of highway subgrade in the alpine meadow area of the QTP.
