During the mining process of impact-prone coal seams,drilling pressure relief can reduce the impact propensity of the coal seam,but it also reduces the integrity and strength of the coal mass at the side of the roadwa...During the mining process of impact-prone coal seams,drilling pressure relief can reduce the impact propensity of the coal seam,but it also reduces the integrity and strength of the coal mass at the side of the roadway.Therefore,studying the mechanical properties and energy evolution rules of coal samples containing holes and filled structures has certain practical significance for achieving coordinated control of coal mine rockburst disasters and the stability of roadway surrounding rocks.To achieve this aim,seven types of burst-prone coal samples were prepared and subject to uniaxial compression experiments with the aid of a TAW-3000 electro-hydraulic servo testing machine.Besides,the stress–strain curves,acoustic emission signals,DIC strain fields and other data were collected during the experiments.Furthermore,the failure modes and energy evolutions of samples with varying drilled hole sizes and filling materials were analyzed.The results show that the indexes related to burst propensity of the drilled coal samples decline to some extent compared with those of the intact one,and the decline is positively corelated to the diameter of the drilled hole.After hole filling,the strain concentration degree around the drilled hole is lowered to a certain degree,and polyurethane filling has a more remarkable effect than cement filling.Meanwhile,hole filling can enhance the strength and deformation resistance of coal.Hole drilling can accelerate the release of accumulated elastic strain energy,turning the acoustic emission events from low-frequency and high-energy ones to high-frequency and low-energy ones,whereas hole filling can reduce the intensity of energy release.The experimental results and theoretical derivation demonstrate that hole filling promotes coal deformability and strength mainly by weakening stress concentration surrounding the drilled holes.Moreover,the fillings can achieve a better filling effect if their elastic modulus and Poisson’s ratio are closer to those of the coal body.展开更多
The scalar-free black hole could be unstable against the scalar field perturbation when it is coupled to a Gauss–Bonnet(GB)invariant in a special form.It is known that the tachyonic instability in this scenario is tr...The scalar-free black hole could be unstable against the scalar field perturbation when it is coupled to a Gauss–Bonnet(GB)invariant in a special form.It is known that the tachyonic instability in this scenario is triggered by the sufficiently strong GB coupling.In this paper,we focus on the time domain analysis of massive scalar field perturbation around the Schwarzschild de-Sitter black hole in Einstein-scalar–Gauss–Bonnet gravity.By analyzing the scalar field propagation,we find that the scalar field will finally grow when the GB coupling is large enough.This could lead to the instability of the background black hole.Furthermore,we demonstrate how the mass of the scalar field and the GB coupling strength affect the onset of tachyonic instability.展开更多
Five sequences of deep fluid injections at the Pohang Enhanced Geothermal System(EGS)triggered an ML 5.4 earthquake on November 15,2017.The foreshock-mainshock-aftershock sequence was monitored using dense seismic net...Five sequences of deep fluid injections at the Pohang Enhanced Geothermal System(EGS)triggered an ML 5.4 earthquake on November 15,2017.The foreshock-mainshock-aftershock sequence was monitored using dense seismic networks.Between November 14,2017,and May 31,2023,this study detected 5,169 earthquakes and determined the relative locations of 4,902 earthquakes,including seven foreshocks.A heterogeneous subsurface fault model is proposed,in which the fault is reactivated by induced and triggered earthquakes.The earthquake frequency decreased after the mainshock,with a temporary increase after the ML 4.6 event on February 10,2018.The magnitude-frequency b-values are significantly lower than those for the background seismicity in the Korean Peninsula and those for the 2016 Gyeongju earthquake sequence.The aftershock decay rate p-values are within the range of typical values,regardless of decreasing over time.The earthquake focal mechanisms exhibit a predominance of strike-slip components,whereas the slip tendency indicates a higher value in reverse faulting geometry,implying stress redistribution after the mainshock.The seismic landscape with ongoing aftershock activity after the 2017 Pohang earthquake underscores the importance of sustained,long-term seismic monitoring to comprehensively grasp the implications of the new seismic environment for seismic hazards in the area.展开更多
In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium sili...In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium silicate/CO_2 method, using a blind riser, and then the desired molten steel was obtained using a coreless induction furnace. The casting was performed at melting temperatures of 1350, 1400, 1450, and 1500°C, and the cast blocks were immediately quenched in water. Optical microscopy was used to analyze the microstructure, and scanning electron microscopy(SEM) and X-ray diffractrometry(XRD) were used to analyze the corrosion morphology and phase formation in the microstructure, respectively. The corrosion behavior of the samples was analyzed using a potentiodynamic polarization test and electrochemical impedance spectroscopy(EIS) in 3.5 wt% NaCl. The optical microscopy observations and XRD patterns show that the increase in melting temperature led to a decrease of carbides and an increase in the austenite grain size in the Hadfield steel microstructure. The corrosion tests results show that with increasing melting temperature in the casting process, Hadfield steel shows a higher corrosion resistance. The SEM images of the corrosion morphologies show that the reduction of melting temperature in the Hadfield steel casting process induced micro-galvanic corrosion conditions.展开更多
Hydrocarbon resources in the Qiongdongnan Basin have become an important exploration target in China.However,the development of high-quality source rocks in this basin,especially in its deep-water areas,are still not ...Hydrocarbon resources in the Qiongdongnan Basin have become an important exploration target in China.However,the development of high-quality source rocks in this basin,especially in its deep-water areas,are still not fully understood.In this study,evolutions of sedimentary facies and palaeoenvironment and their influences on the development of source rocks in diverse tectonic regions of the Qiongdongnan Basin were investigated.The results show that during the Oligocene and to Miocene periods,the sedimentary environment of this basin progressively varied from a semi-closed gulf to an open marine environment,which resulted in significant differences in palaeoenvironmental conditions of the water column for various tectonic regions of the basin.In shallow-water areas,the palaeoproductivity and reducibility successively decrease,and the hydrodynamic intensity gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In deep-water areas,the water column of the Yacheng and Lingshui strata has a higher palaeoproductivity and a weaker hydrodynamic intensity than that of the Sanya-Meishan strata,while the reducibility gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In general,the palaeoenvironmental conditions of the water column are the most favorable to the development of the Yacheng organic-rich source rocks.Meanwhile,the Miocene marine source rocks in the deep-water areas of the Qiongdongnan Basin may also have a certain hydrocarbon potential.The differences in the development models of source rocks in various tectonic regions of continental margin basins should be fully evaluated in the exploration and development of hydrocarbons.展开更多
In this study, the structures and evolutions of moderate(MO) explosive cyclones(ECs) over the Northwestern Pacific(NWP) and Northeastern Pacific(NEP) are investigated and compared using composite analysis with cyclone...In this study, the structures and evolutions of moderate(MO) explosive cyclones(ECs) over the Northwestern Pacific(NWP) and Northeastern Pacific(NEP) are investigated and compared using composite analysis with cyclone-relative coordinates. Final Operational Global Analysis data gathered during the cold seasons(October–April) of the 15 years from 2000 to 2015 are used. The results indicate that MO NWP ECs have strong baroclinicity and abundant latent heat release at low levels and strong upper-level forcing, which favors explosive cyclogenesis. The rapid development of MO NEP ECs results from their interaction with a northern cyclone and a large middle-level advection of cyclonic vorticity. The structural differences between MO NWP ECs and MO NEP ECs are significant. This results from their specific large-scale atmospheric and oceanic environments. MO NWP ECs usually develop rapidly in the east and southeast of the Japan Islands; the intrusion of cold dry air from the East Asian continent leads to strong baroclinicity, and the Kuroshio/Kuroshio Extension provides abundant latent heat release at low levels. The East Asian subtropical westerly jet stream supplies strong upper-level forcing. While MO NEP ECs mainly occur over the NEP, the low-level baroclinicity, upper-level jet stream, and warm ocean currents are relatively weaker. The merged cyclone associated with a strong middle-level trough transports large cyclonic vorticity to MO NEP ECs, which favors their rapid development.展开更多
To solve the wall-wetting problem in internal combustion engines,the physical and chemical etching methods are used to prepare different wettability surfaces with various microstructures.The evaporation characteristic...To solve the wall-wetting problem in internal combustion engines,the physical and chemical etching methods are used to prepare different wettability surfaces with various microstructures.The evaporation characteristics and morphological evolution processes of diesel and n-butanol droplets after hitting the various surfaces are investigated.The results show that the surface microstructures increase the surface roughness(Ra),enhancing the oleophilic property of the oleophilic surfaces.Compared with n-butanol droplets,the same surface shows stronger oleophobicity to diesel droplets.When a droplet hits an oleophilic property surface with a lower temperature,the stronger the oleophilicity,the shorter the evaporation time.For oleophilic surfaces,larger Ra leads to a higher Leidenfrost temperature(TLeid).The low TLeid caused by enhanced oleophobicity,dense microstructures and increased convex dome height facilitates droplet rebound and promotes the evaporation of the wall-impinging droplets into the cylinder.The evaporation rate of the droplets is not only related to the characteristics of the solid surfaces and the fuel droplets but also affected by the heat transfer rate to the droplets in different boiling regimes.The spreading diameter of a droplet on an oleophobic surface varies significantly less with time than that on an oleophilic surface under the same surface temperature.展开更多
The program to predict the microstructure evolutions during hot strip rolling of C-M n steels has been developed in this paper, BV using this program, the microstructure changes with the processing parameters were ana...The program to predict the microstructure evolutions during hot strip rolling of C-M n steels has been developed in this paper, BV using this program, the microstructure changes with the processing parameters were analysed in detail. showing not only a good agreement of prediction with the measured values, but also entirely possibility to optimize hot strip rolling precess by computer simulation展开更多
For the three-body problem, we consider the Lagrange stability. To analyze the stability, along with integrals of energy and angular momentum, we use relations by the author from [1], which band together separately sq...For the three-body problem, we consider the Lagrange stability. To analyze the stability, along with integrals of energy and angular momentum, we use relations by the author from [1], which band together separately squared mutual distances between bodies (mass points) and squared distances from bodies to the barycenter of the system. In this case, we prove the Lagrange stability theorem, which allows us to define more exactly the character of hyperbolic-elliptic and parabolic-elliptic final evolutions.展开更多
Through molecular dynamics（MD） simulation, the dependencies of temperature, grain size and strain rate on the mechanical properties were studied. The simulation results demonstrated that the strain rate from 0.05 to...Through molecular dynamics（MD） simulation, the dependencies of temperature, grain size and strain rate on the mechanical properties were studied. The simulation results demonstrated that the strain rate from 0.05 to 2 ns–1 affected the Young＇s modulus of nickel nanowires slightly, whereas the yield stress increased. The Young＇s modulus decreased approximately linearly; however, the yield stress firstly increased and subsequently dropped as the temperature increased. The Young＇s modulus and yield stress increased as the mean grain size increased from 2.66 to 6.72 nm. Moreover, certain efforts have been made in the microstructure evolution with mechanical properties association under uniaxial tension. Certain phenomena such as the formation of twin structures, which were found in nanowires with larger grain size at higher strain rate and lower temperature, as well as the movement of grain boundaries and dislocation, were detected and discussed in detail. The results demonstrated that the plastic deformation was mainly accommodated by the motion of grain boundaries for smaller grain size. However, for larger grain size, the formations of stacking faults and twins were the main mechanisms of plastic deformation in the polycrystalline nickel nanowire.展开更多
Systematical researches were accomplished on WC-Co with different Co contents(6%,10%and 12%,mass fraction).Based on the XPS and EDX,from orthogonal pretreatment experiments,it is indicated that the acid concentration,...Systematical researches were accomplished on WC-Co with different Co contents(6%,10%and 12%,mass fraction).Based on the XPS and EDX,from orthogonal pretreatment experiments,it is indicated that the acid concentration,the time of the acid pretreatment and the original Co content have significant influences on the Co-removal depth(D).Moreover,the specimen temperature,original Co content and Co-removal depth dependences of the Co evolution in nucleation,heating(in pure H2 atmosphere)and growth experiments were discussed,and mechanisms of Co evolutions were summarized,providing sufficient theoretical bases for the deposition of high-quality diamond films on WC-Co substrates,especially Co-rich WC-Co substrates.It is proven that the Co-rich substrate often presents rapid Co diffusion.The high substrate temperature can promote the Co diffusion in the pretreated substrate,while acts as a Co-etching process for the untreated substrates.It is finally found that the appropriate Co-removal depth for the WC-12%Co substrate is 8-9μm.展开更多
Emergence refers to the existence or formation of collective behaviors in complex systems.Here,we develop a theoretical framework based on the eigen microstate theory to analyze the emerging phenomena and dynamic evol...Emergence refers to the existence or formation of collective behaviors in complex systems.Here,we develop a theoretical framework based on the eigen microstate theory to analyze the emerging phenomena and dynamic evolution of complex system.In this framework,the statistical ensemble composed of M microstates of a complex system with N agents is defined by the normalized N×M matrix A,whose columns represent microstates and order of row is consist with the time.The ensemble matrix A can be decomposed as■,where r=min(N,M),eigenvalueσIbehaves as the probability amplitude of the eigen microstate U_I so that■and U_I evolves following V_I.In a disorder complex system,there is no dominant eigenvalue and eigen microstate.When a probability amplitudeσIbecomes finite in the thermodynamic limit,there is a condensation of the eigen microstate UIin analogy to the Bose–Einstein condensation of Bose gases.This indicates the emergence of U_I and a phase transition in complex system.Our framework has been applied successfully to equilibrium threedimensional Ising model,climate system and stock markets.We anticipate that our eigen microstate method can be used to study non-equilibrium complex systems with unknown orderparameters,such as phase transitions of collective motion and tipping points in climate systems and ecosystems.展开更多
A solid/liquid continuous casting and composite technology was used to produce d8.5 mm brass cladding pure copper stranded wire composite billet and the composite billet was then drawn. The results showed that the com...A solid/liquid continuous casting and composite technology was used to produce d8.5 mm brass cladding pure copper stranded wire composite billet and the composite billet was then drawn. The results showed that the composite billet had good surface quality, metallurgical bonding interface between brass and pure copper as well as elongation of 53.1%. Synergistic deformation degree between pure copper wire and brass cladding layer was high during drawing. With an increase of the total deformation amount, the plastic deformation of the pure copper wire reduced triangular arc gaps between the pure copper wires and the triangular arc gaps were fully filled at 50%. When the total deformation amount was increased to 63%, dislocation cells and microbands successively formed in the pure copper wire. In the brass cladding layer, planar dislocation networks, twins and shear bands formed successively, and the main deformation mechanisms were dislocation sliding, twinning and shear deformation. The tensile strength increased from 240 MPa of the composite billet to 519 MPa of the one with the deformation amount of 63%, but the elongation decreased from 53.1% to 3.2%. A process of solid/liquid continuous casting and composite forming→drawing can work as a new compact method to produce brass cladding pure copper stranded wire composite as railway through grounding wire.展开更多
The microstructural evolution of AA7055 aluminum alloy under dynamic impact loading with the strain rate of 1.3 × 10^4 s^-1 controlled by a split Hopkinson pressure bar was investigated, and compared with that un...The microstructural evolution of AA7055 aluminum alloy under dynamic impact loading with the strain rate of 1.3 × 10^4 s^-1 controlled by a split Hopkinson pressure bar was investigated, and compared with that under quasi-static mechanical loading in compression with strain rate of 1.0 × 10^-3 s^-1. The quasi-static-compressed sample exhibited equiaxed dislocation cells, which were different from the elongated and incomplete dislocation cells for the alloy undergoing dynamic compression. The high strain-rate compression also induced the formation of localized shear bands in which the recrystallizations characterized as fine equiaxed grains were observed. The microstructural evolutions under both quasi-static and dynamic compressions are rationalized in terms of the dislocation cell model combined with the dislocation kinetics, in addition to the adiabatic temperature rise in shear bands at high strain rate.展开更多
The structure evolutions of ZL109 alloy and 7050 alloy were studied in the processes of preparing raw billets by low super heat casting, remelting the raw billets, semisolid forming and heat treating components. The t...The structure evolutions of ZL109 alloy and 7050 alloy were studied in the processes of preparing raw billets by low super heat casting, remelting the raw billets, semisolid forming and heat treating components. The thin and symmetrical structure was obtained by using low super heat casting process. The eutectic that lied in the raw billet of ZL109 alloy remelted and produced liquid phase in the process of remelting, but to the 7050 alloy, the eutectic of intergranular and the pointedness of grains was remelted to make the grains more uniform and smooth. In the process of semisolid forming, the primary α and the eutectic inside the ZL109 alloy were separated partly and the grains in the 7050 alloy was conglutinated together. After heat treatment, the eutectic α grains of ZL109 traveled to primary α and shaped the white fishing net like organization; the eutectic Si grains assembled into the black massive particles. As to 7050, after heat treatment, α particles recrystallized and thin grains pattern was obtained.展开更多
The evolution of the microstructure and mechanical properties of alloy system with nominally composition Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd(x=0,1.2,2.4,3.6,4.8,6)is evaluated based on computational phase diagram and correspon...The evolution of the microstructure and mechanical properties of alloy system with nominally composition Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd(x=0,1.2,2.4,3.6,4.8,6)is evaluated based on computational phase diagram and corresponding experimental studies.The results show that grains are significantly refined with the increase of Gd content.The main phases of as-cast alloys areα-Mg,β-Li,AgLi_(2)Mg,and Mg_(3)Gd.With the increase of Gd content,the amounts of Mg_(3)Gd phase andβ-Li phase have been increased.When the Gd content exceeds 3.6 wt%,Mg_(3)Gd phase precipitates in a form of the network at the grain boundaries.The precipitation ofβ-Li can be attributed to the competitive dissolution of Zn,Gd,and Li in Mg.Meanwhile,γ″is formed after the addition of Gd,which grows and transforms intoγ′with the increase of Gd content.In solidification process,stacking faults are formed by solid transformation of partialα-Mg and Mg_(3)Gd.Eventually,with the synergistic effect of Mg_(3)Gd,β-Li,andγ″(orγ′),as the Gd content increasing,the tensile strength of the alloy first increases,then decreases,and the elongation decreases.When the content of Gd is 4.8 wt%,the ultimate tensile strength and yield strength reach the maximum values of 227 MPa and 139 MPa,and the elongation is 18.1%,respectively.展开更多
Industrial revolutions have a profound impact on energy and metal demand.Based on technological improvement,industrial transformation,and changes of energy and metal consumption in the United States,this paper identif...Industrial revolutions have a profound impact on energy and metal demand.Based on technological improvement,industrial transformation,and changes of energy and metal consumption in the United States,this paper identified the evolution characteristics of energy and metal demand driven by industrial revolutions,and analyzed the trends of energy and metal demand driven by the fourth industrial revolution which is happening currently.Results indicated that fossil fuels were the major energy sources which boosted up the past three industrial revolutions,whereas their consumption increased at a slowing pace as the economy was growing continually;after the third industrial revolution,the consumption of fossil fuels decoupled gradually with the economic growth.As the industrial structure transformed as the industrial revolutions went on,more and more metals were used in the industries,and the consumption of different metals showed different trends.In recent years,a new technological revolution has surged mainly driven by the overall application of new information technologies.The technological advance in information,new energies,new materials,etc.,will speed up the industrial transformation and exert a deep effect on the demand of energy and metals.It can be inferred that the ratio of clean,non-polluting,renewable energy will rise while the ratio of fossil fuels will drop in the energy demand,and the demand of rare metals will perhaps enter a fast-growing period,while the demand of traditional bulk metals will fluctuate at mid-high levels.Following the new industrial revolution,China should adopt an energy transition strategy of developing low-carbon and free-carbon technologies simultaneously,reinforce the domestic and international metal supply system with the aim of enhancing global governance capability,strengthen the deep development of rich rare metals and broaden the overseas supply channels of scare rare metals.展开更多
A theoretical model for calculating spontaneous and stimulated Brillouin scattering（SBS） spectra is described. An empirical formula for the Stokes output spectral linewidth, a function of spontaneous Brillouin linew...A theoretical model for calculating spontaneous and stimulated Brillouin scattering（SBS） spectra is described. An empirical formula for the Stokes output spectral linewidth, a function of spontaneous Brillouin linewidth and the exponential gain coefficient, is obtained by the calculated data fitting. The formula holds true for two cases involving pump undepletion and depletion. The lineshape change from spontaneous to highly pump-depleted SBS spectra is also investigated. The result shows that for the pump power below the SBS threshold, the Stokes output spectral lincshape evolves from Lorentzian to approximately Gaussian as the pump power increases. For the pump power near or beyond the threshold, the SBS spectrum is in the form of a steady Gaussian profile, and the spectral linewidth comes to a certain value about 7 times narrower than the spontaneous one. The theoretical results are experimentally demonstrated by using several common liquid media.展开更多
Structural, electronic, and magnetic properties of AunGd (n = 6-15) small clusters are investigated by using first principles spin polarized calculations and combining with the ab-initio evolutionary structure simulat...Structural, electronic, and magnetic properties of AunGd (n = 6-15) small clusters are investigated by using first principles spin polarized calculations and combining with the ab-initio evolutionary structure simulations. The calculated binding energies indicate that after doping a Gd atom AunGd cluster is obviously more stable than a pure AUn+l cluster. Au6Gd with the quasiplanar structure has a largest magnetic moment of 7.421 gB. The Gd-4f electrons play an important role in determining the high magnetic moments of AunGd clusters, but in Au6Gd and Aul2Gd clusters the unignorable spin polarized effects from the Au-6s and Au-5d electrons further enhance their magnetism. The HOMO-LUMO (here, HOMO and LUMO stand for the highest occupied molecular orbital, and the lowest unoccupied molecular orbital, respectively) energy gaps of munGd clusters are smaller than those of pure AUn+l clusters, indicating that AunGd clusters have potential as new catalysts with enhanced reactivity.展开更多
基金National Natural Science Foundation of China(Grant Nos.52174080 and 51974160)Science Foundation of Tiandi Technology Co.,Ltd.(2022-2-TD-ZD016).
文摘During the mining process of impact-prone coal seams,drilling pressure relief can reduce the impact propensity of the coal seam,but it also reduces the integrity and strength of the coal mass at the side of the roadway.Therefore,studying the mechanical properties and energy evolution rules of coal samples containing holes and filled structures has certain practical significance for achieving coordinated control of coal mine rockburst disasters and the stability of roadway surrounding rocks.To achieve this aim,seven types of burst-prone coal samples were prepared and subject to uniaxial compression experiments with the aid of a TAW-3000 electro-hydraulic servo testing machine.Besides,the stress–strain curves,acoustic emission signals,DIC strain fields and other data were collected during the experiments.Furthermore,the failure modes and energy evolutions of samples with varying drilled hole sizes and filling materials were analyzed.The results show that the indexes related to burst propensity of the drilled coal samples decline to some extent compared with those of the intact one,and the decline is positively corelated to the diameter of the drilled hole.After hole filling,the strain concentration degree around the drilled hole is lowered to a certain degree,and polyurethane filling has a more remarkable effect than cement filling.Meanwhile,hole filling can enhance the strength and deformation resistance of coal.Hole drilling can accelerate the release of accumulated elastic strain energy,turning the acoustic emission events from low-frequency and high-energy ones to high-frequency and low-energy ones,whereas hole filling can reduce the intensity of energy release.The experimental results and theoretical derivation demonstrate that hole filling promotes coal deformability and strength mainly by weakening stress concentration surrounding the drilled holes.Moreover,the fillings can achieve a better filling effect if their elastic modulus and Poisson’s ratio are closer to those of the coal body.
基金partly supported by Natural Science Foundation of China under Grant No.12375054the Natural Science Foundation of Jiangsu Province under Grant No.BK20211601。
文摘The scalar-free black hole could be unstable against the scalar field perturbation when it is coupled to a Gauss–Bonnet(GB)invariant in a special form.It is known that the tachyonic instability in this scenario is triggered by the sufficiently strong GB coupling.In this paper,we focus on the time domain analysis of massive scalar field perturbation around the Schwarzschild de-Sitter black hole in Einstein-scalar–Gauss–Bonnet gravity.By analyzing the scalar field propagation,we find that the scalar field will finally grow when the GB coupling is large enough.This could lead to the instability of the background black hole.Furthermore,we demonstrate how the mass of the scalar field and the GB coupling strength affect the onset of tachyonic instability.
基金funded by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant from the Ministry of Trade,Industry and Energy(MOTIE)(No.20198210100030,20208310100020)the Nuclear Safety Research Program through the Korea Foundation of Nuclear Safety(KoFONS)grant from the Nuclear Safety and Security Commission(NSSC)(No.071610)of the Republic of Korea.
文摘Five sequences of deep fluid injections at the Pohang Enhanced Geothermal System(EGS)triggered an ML 5.4 earthquake on November 15,2017.The foreshock-mainshock-aftershock sequence was monitored using dense seismic networks.Between November 14,2017,and May 31,2023,this study detected 5,169 earthquakes and determined the relative locations of 4,902 earthquakes,including seven foreshocks.A heterogeneous subsurface fault model is proposed,in which the fault is reactivated by induced and triggered earthquakes.The earthquake frequency decreased after the mainshock,with a temporary increase after the ML 4.6 event on February 10,2018.The magnitude-frequency b-values are significantly lower than those for the background seismicity in the Korean Peninsula and those for the 2016 Gyeongju earthquake sequence.The aftershock decay rate p-values are within the range of typical values,regardless of decreasing over time.The earthquake focal mechanisms exhibit a predominance of strike-slip components,whereas the slip tendency indicates a higher value in reverse faulting geometry,implying stress redistribution after the mainshock.The seismic landscape with ongoing aftershock activity after the 2017 Pohang earthquake underscores the importance of sustained,long-term seismic monitoring to comprehensively grasp the implications of the new seismic environment for seismic hazards in the area.
文摘In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium silicate/CO_2 method, using a blind riser, and then the desired molten steel was obtained using a coreless induction furnace. The casting was performed at melting temperatures of 1350, 1400, 1450, and 1500°C, and the cast blocks were immediately quenched in water. Optical microscopy was used to analyze the microstructure, and scanning electron microscopy(SEM) and X-ray diffractrometry(XRD) were used to analyze the corrosion morphology and phase formation in the microstructure, respectively. The corrosion behavior of the samples was analyzed using a potentiodynamic polarization test and electrochemical impedance spectroscopy(EIS) in 3.5 wt% NaCl. The optical microscopy observations and XRD patterns show that the increase in melting temperature led to a decrease of carbides and an increase in the austenite grain size in the Hadfield steel microstructure. The corrosion tests results show that with increasing melting temperature in the casting process, Hadfield steel shows a higher corrosion resistance. The SEM images of the corrosion morphologies show that the reduction of melting temperature in the Hadfield steel casting process induced micro-galvanic corrosion conditions.
基金supported by the National Natural Science Foundation of China(42272162)the Natural Science Foundation of Guangdong Province(2021A1515011381 and 2021A1515011635)the Science Project of the CNOOC(KJZH-2021-0003-00).
文摘Hydrocarbon resources in the Qiongdongnan Basin have become an important exploration target in China.However,the development of high-quality source rocks in this basin,especially in its deep-water areas,are still not fully understood.In this study,evolutions of sedimentary facies and palaeoenvironment and their influences on the development of source rocks in diverse tectonic regions of the Qiongdongnan Basin were investigated.The results show that during the Oligocene and to Miocene periods,the sedimentary environment of this basin progressively varied from a semi-closed gulf to an open marine environment,which resulted in significant differences in palaeoenvironmental conditions of the water column for various tectonic regions of the basin.In shallow-water areas,the palaeoproductivity and reducibility successively decrease,and the hydrodynamic intensity gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In deep-water areas,the water column of the Yacheng and Lingshui strata has a higher palaeoproductivity and a weaker hydrodynamic intensity than that of the Sanya-Meishan strata,while the reducibility gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In general,the palaeoenvironmental conditions of the water column are the most favorable to the development of the Yacheng organic-rich source rocks.Meanwhile,the Miocene marine source rocks in the deep-water areas of the Qiongdongnan Basin may also have a certain hydrocarbon potential.The differences in the development models of source rocks in various tectonic regions of continental margin basins should be fully evaluated in the exploration and development of hydrocarbons.
基金the National Natural Science Foundation of China for financial support (Nos. 41275049 and 41775042)
文摘In this study, the structures and evolutions of moderate(MO) explosive cyclones(ECs) over the Northwestern Pacific(NWP) and Northeastern Pacific(NEP) are investigated and compared using composite analysis with cyclone-relative coordinates. Final Operational Global Analysis data gathered during the cold seasons(October–April) of the 15 years from 2000 to 2015 are used. The results indicate that MO NWP ECs have strong baroclinicity and abundant latent heat release at low levels and strong upper-level forcing, which favors explosive cyclogenesis. The rapid development of MO NEP ECs results from their interaction with a northern cyclone and a large middle-level advection of cyclonic vorticity. The structural differences between MO NWP ECs and MO NEP ECs are significant. This results from their specific large-scale atmospheric and oceanic environments. MO NWP ECs usually develop rapidly in the east and southeast of the Japan Islands; the intrusion of cold dry air from the East Asian continent leads to strong baroclinicity, and the Kuroshio/Kuroshio Extension provides abundant latent heat release at low levels. The East Asian subtropical westerly jet stream supplies strong upper-level forcing. While MO NEP ECs mainly occur over the NEP, the low-level baroclinicity, upper-level jet stream, and warm ocean currents are relatively weaker. The merged cyclone associated with a strong middle-level trough transports large cyclonic vorticity to MO NEP ECs, which favors their rapid development.
基金the National Natural Science Foundation of China(Project code:51676084)Jilin Province Specific Project of Industrial Technology Research&Development(Project code:2020C025-2)+2 种基金Natural Science Foundation of Jilin Province(Project code:20220101212JC)Free Exploration Project of Changsha Automotive Innovation Research Institute of Jilin University(Project code:JCZT20220202)2021“Interdisciplinary Integration and Innovation”Project of Jilin University(Project code:XJRCYB07).
文摘To solve the wall-wetting problem in internal combustion engines,the physical and chemical etching methods are used to prepare different wettability surfaces with various microstructures.The evaporation characteristics and morphological evolution processes of diesel and n-butanol droplets after hitting the various surfaces are investigated.The results show that the surface microstructures increase the surface roughness(Ra),enhancing the oleophilic property of the oleophilic surfaces.Compared with n-butanol droplets,the same surface shows stronger oleophobicity to diesel droplets.When a droplet hits an oleophilic property surface with a lower temperature,the stronger the oleophilicity,the shorter the evaporation time.For oleophilic surfaces,larger Ra leads to a higher Leidenfrost temperature(TLeid).The low TLeid caused by enhanced oleophobicity,dense microstructures and increased convex dome height facilitates droplet rebound and promotes the evaporation of the wall-impinging droplets into the cylinder.The evaporation rate of the droplets is not only related to the characteristics of the solid surfaces and the fuel droplets but also affected by the heat transfer rate to the droplets in different boiling regimes.The spreading diameter of a droplet on an oleophobic surface varies significantly less with time than that on an oleophilic surface under the same surface temperature.
文摘The program to predict the microstructure evolutions during hot strip rolling of C-M n steels has been developed in this paper, BV using this program, the microstructure changes with the processing parameters were analysed in detail. showing not only a good agreement of prediction with the measured values, but also entirely possibility to optimize hot strip rolling precess by computer simulation
文摘For the three-body problem, we consider the Lagrange stability. To analyze the stability, along with integrals of energy and angular momentum, we use relations by the author from [1], which band together separately squared mutual distances between bodies (mass points) and squared distances from bodies to the barycenter of the system. In this case, we prove the Lagrange stability theorem, which allows us to define more exactly the character of hyperbolic-elliptic and parabolic-elliptic final evolutions.
基金Supported by the National Natural Science Foundation of China(11102139,11472195)the Natural Science Foundation of Hubei Province of China(2014CFB713)
文摘Through molecular dynamics（MD） simulation, the dependencies of temperature, grain size and strain rate on the mechanical properties were studied. The simulation results demonstrated that the strain rate from 0.05 to 2 ns–1 affected the Young＇s modulus of nickel nanowires slightly, whereas the yield stress increased. The Young＇s modulus decreased approximately linearly; however, the yield stress firstly increased and subsequently dropped as the temperature increased. The Young＇s modulus and yield stress increased as the mean grain size increased from 2.66 to 6.72 nm. Moreover, certain efforts have been made in the microstructure evolution with mechanical properties association under uniaxial tension. Certain phenomena such as the formation of twin structures, which were found in nanowires with larger grain size at higher strain rate and lower temperature, as well as the movement of grain boundaries and dislocation, were detected and discussed in detail. The results demonstrated that the plastic deformation was mainly accommodated by the motion of grain boundaries for smaller grain size. However, for larger grain size, the formations of stacking faults and twins were the main mechanisms of plastic deformation in the polycrystalline nickel nanowire.
基金Projects(51275302,51005154)supported by the National Natural Science Foundation of ChinaProject(2015M580327)supported by the China Postdoctoral Science FoundationProject(2016T90370)supported by the China Postdoctoral Science Foundation Special Funded Project
文摘Systematical researches were accomplished on WC-Co with different Co contents(6%,10%and 12%,mass fraction).Based on the XPS and EDX,from orthogonal pretreatment experiments,it is indicated that the acid concentration,the time of the acid pretreatment and the original Co content have significant influences on the Co-removal depth(D).Moreover,the specimen temperature,original Co content and Co-removal depth dependences of the Co evolution in nucleation,heating(in pure H2 atmosphere)and growth experiments were discussed,and mechanisms of Co evolutions were summarized,providing sufficient theoretical bases for the deposition of high-quality diamond films on WC-Co substrates,especially Co-rich WC-Co substrates.It is proven that the Co-rich substrate often presents rapid Co diffusion.The high substrate temperature can promote the Co diffusion in the pretreated substrate,while acts as a Co-etching process for the untreated substrates.It is finally found that the appropriate Co-removal depth for the WC-12%Co substrate is 8-9μm.
基金supported by the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(Grant No.QYZD-SSW-SYS019)。
文摘Emergence refers to the existence or formation of collective behaviors in complex systems.Here,we develop a theoretical framework based on the eigen microstate theory to analyze the emerging phenomena and dynamic evolution of complex system.In this framework,the statistical ensemble composed of M microstates of a complex system with N agents is defined by the normalized N×M matrix A,whose columns represent microstates and order of row is consist with the time.The ensemble matrix A can be decomposed as■,where r=min(N,M),eigenvalueσIbehaves as the probability amplitude of the eigen microstate U_I so that■and U_I evolves following V_I.In a disorder complex system,there is no dominant eigenvalue and eigen microstate.When a probability amplitudeσIbecomes finite in the thermodynamic limit,there is a condensation of the eigen microstate UIin analogy to the Bose–Einstein condensation of Bose gases.This indicates the emergence of U_I and a phase transition in complex system.Our framework has been applied successfully to equilibrium threedimensional Ising model,climate system and stock markets.We anticipate that our eigen microstate method can be used to study non-equilibrium complex systems with unknown orderparameters,such as phase transitions of collective motion and tipping points in climate systems and ecosystems.
基金Project(51104016)supported by the National Natural Science Foundation of ChinaProject(51925401)supported by the National Natural Science Foundation for Distinguished Young Scholars of ChinaProject(2019B10087)supported by Ningbo Science and Technology Innovation 2025 Major Project,China。
文摘A solid/liquid continuous casting and composite technology was used to produce d8.5 mm brass cladding pure copper stranded wire composite billet and the composite billet was then drawn. The results showed that the composite billet had good surface quality, metallurgical bonding interface between brass and pure copper as well as elongation of 53.1%. Synergistic deformation degree between pure copper wire and brass cladding layer was high during drawing. With an increase of the total deformation amount, the plastic deformation of the pure copper wire reduced triangular arc gaps between the pure copper wires and the triangular arc gaps were fully filled at 50%. When the total deformation amount was increased to 63%, dislocation cells and microbands successively formed in the pure copper wire. In the brass cladding layer, planar dislocation networks, twins and shear bands formed successively, and the main deformation mechanisms were dislocation sliding, twinning and shear deformation. The tensile strength increased from 240 MPa of the composite billet to 519 MPa of the one with the deformation amount of 63%, but the elongation decreased from 53.1% to 3.2%. A process of solid/liquid continuous casting and composite forming→drawing can work as a new compact method to produce brass cladding pure copper stranded wire composite as railway through grounding wire.
基金financially supported by the National Basic Research Program of China (No.G2011CB012806)
文摘The microstructural evolution of AA7055 aluminum alloy under dynamic impact loading with the strain rate of 1.3 × 10^4 s^-1 controlled by a split Hopkinson pressure bar was investigated, and compared with that under quasi-static mechanical loading in compression with strain rate of 1.0 × 10^-3 s^-1. The quasi-static-compressed sample exhibited equiaxed dislocation cells, which were different from the elongated and incomplete dislocation cells for the alloy undergoing dynamic compression. The high strain-rate compression also induced the formation of localized shear bands in which the recrystallizations characterized as fine equiaxed grains were observed. The microstructural evolutions under both quasi-static and dynamic compressions are rationalized in terms of the dislocation cell model combined with the dislocation kinetics, in addition to the adiabatic temperature rise in shear bands at high strain rate.
文摘The structure evolutions of ZL109 alloy and 7050 alloy were studied in the processes of preparing raw billets by low super heat casting, remelting the raw billets, semisolid forming and heat treating components. The thin and symmetrical structure was obtained by using low super heat casting process. The eutectic that lied in the raw billet of ZL109 alloy remelted and produced liquid phase in the process of remelting, but to the 7050 alloy, the eutectic of intergranular and the pointedness of grains was remelted to make the grains more uniform and smooth. In the process of semisolid forming, the primary α and the eutectic inside the ZL109 alloy were separated partly and the grains in the 7050 alloy was conglutinated together. After heat treatment, the eutectic α grains of ZL109 traveled to primary α and shaped the white fishing net like organization; the eutectic Si grains assembled into the black massive particles. As to 7050, after heat treatment, α particles recrystallized and thin grains pattern was obtained.
基金supported by the National Natural Science Foundation of China(Nos.51871068,51971071,52011530025,and U21A2049)the National Key Research and Development Program of China(No.2021YFE0103200)+2 种基金the Zhejiang Province Key Research and Development Program(No.2021C01086)the Open Foundation of Key Laboratory of Superlight Materials&Surface Technology of Ministry of Education(Nos.HEU10202113 and HEU10202202)the Natural Science Foundation of Heilongjiang Province(No.LH2019E086).
文摘The evolution of the microstructure and mechanical properties of alloy system with nominally composition Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd(x=0,1.2,2.4,3.6,4.8,6)is evaluated based on computational phase diagram and corresponding experimental studies.The results show that grains are significantly refined with the increase of Gd content.The main phases of as-cast alloys areα-Mg,β-Li,AgLi_(2)Mg,and Mg_(3)Gd.With the increase of Gd content,the amounts of Mg_(3)Gd phase andβ-Li phase have been increased.When the Gd content exceeds 3.6 wt%,Mg_(3)Gd phase precipitates in a form of the network at the grain boundaries.The precipitation ofβ-Li can be attributed to the competitive dissolution of Zn,Gd,and Li in Mg.Meanwhile,γ″is formed after the addition of Gd,which grows and transforms intoγ′with the increase of Gd content.In solidification process,stacking faults are formed by solid transformation of partialα-Mg and Mg_(3)Gd.Eventually,with the synergistic effect of Mg_(3)Gd,β-Li,andγ″(orγ′),as the Gd content increasing,the tensile strength of the alloy first increases,then decreases,and the elongation decreases.When the content of Gd is 4.8 wt%,the ultimate tensile strength and yield strength reach the maximum values of 227 MPa and 139 MPa,and the elongation is 18.1%,respectively.
文摘Industrial revolutions have a profound impact on energy and metal demand.Based on technological improvement,industrial transformation,and changes of energy and metal consumption in the United States,this paper identified the evolution characteristics of energy and metal demand driven by industrial revolutions,and analyzed the trends of energy and metal demand driven by the fourth industrial revolution which is happening currently.Results indicated that fossil fuels were the major energy sources which boosted up the past three industrial revolutions,whereas their consumption increased at a slowing pace as the economy was growing continually;after the third industrial revolution,the consumption of fossil fuels decoupled gradually with the economic growth.As the industrial structure transformed as the industrial revolutions went on,more and more metals were used in the industries,and the consumption of different metals showed different trends.In recent years,a new technological revolution has surged mainly driven by the overall application of new information technologies.The technological advance in information,new energies,new materials,etc.,will speed up the industrial transformation and exert a deep effect on the demand of energy and metals.It can be inferred that the ratio of clean,non-polluting,renewable energy will rise while the ratio of fossil fuels will drop in the energy demand,and the demand of rare metals will perhaps enter a fast-growing period,while the demand of traditional bulk metals will fluctuate at mid-high levels.Following the new industrial revolution,China should adopt an energy transition strategy of developing low-carbon and free-carbon technologies simultaneously,reinforce the domestic and international metal supply system with the aim of enhancing global governance capability,strengthen the deep development of rich rare metals and broaden the overseas supply channels of scare rare metals.
基金Project supported by the National Natural Science Foundation of China (Grant No 60778019)the Program of Excellent Teamin Harbin Institute of Technology, Chinathe Program of Science and Technology of Education the Bureau of Heilongjiang Province, China (Grant No 11521048)
文摘A theoretical model for calculating spontaneous and stimulated Brillouin scattering（SBS） spectra is described. An empirical formula for the Stokes output spectral linewidth, a function of spontaneous Brillouin linewidth and the exponential gain coefficient, is obtained by the calculated data fitting. The formula holds true for two cases involving pump undepletion and depletion. The lineshape change from spontaneous to highly pump-depleted SBS spectra is also investigated. The result shows that for the pump power below the SBS threshold, the Stokes output spectral lincshape evolves from Lorentzian to approximately Gaussian as the pump power increases. For the pump power near or beyond the threshold, the SBS spectrum is in the form of a steady Gaussian profile, and the spectral linewidth comes to a certain value about 7 times narrower than the spontaneous one. The theoretical results are experimentally demonstrated by using several common liquid media.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB643703)the National Natural Science Foundation of China(Grant Nos.11464008 and 51401060)+1 种基金the Natural Science Foundation of Guangxi Zhuang Autonomous Region,China(Grant Nos.2014GXNSFGA118001 and 2016GXNSFGA380001)the Guangxi Provincial Key Laboratory of Information Materials(Grant Nos.1210908-215-Z and 131022-Z)
文摘Structural, electronic, and magnetic properties of AunGd (n = 6-15) small clusters are investigated by using first principles spin polarized calculations and combining with the ab-initio evolutionary structure simulations. The calculated binding energies indicate that after doping a Gd atom AunGd cluster is obviously more stable than a pure AUn+l cluster. Au6Gd with the quasiplanar structure has a largest magnetic moment of 7.421 gB. The Gd-4f electrons play an important role in determining the high magnetic moments of AunGd clusters, but in Au6Gd and Aul2Gd clusters the unignorable spin polarized effects from the Au-6s and Au-5d electrons further enhance their magnetism. The HOMO-LUMO (here, HOMO and LUMO stand for the highest occupied molecular orbital, and the lowest unoccupied molecular orbital, respectively) energy gaps of munGd clusters are smaller than those of pure AUn+l clusters, indicating that AunGd clusters have potential as new catalysts with enhanced reactivity.
