Mine filling materials urgently need to improve mechanical properties and achieve low-carbon transformation.This study explores the mechanism of the synergistic effect of optimizing aggregate fractal grading and intro...Mine filling materials urgently need to improve mechanical properties and achieve low-carbon transformation.This study explores the mechanism of the synergistic effect of optimizing aggregate fractal grading and introducing CO_(2)nanobubble technology to improve the performance of cement-fly ash-based backfill materials(CFB).The properties including fluidity,setting time,uniaxial compressive strength,elastic modulus,porosity,microstructure and CO_(2)storage performance were systematically studied through methods such as fluidity evaluation,time test,uniaxial compression test,mercury intrusion porosimetry(MIP),scanning electron microscopy-energy dispersive spectroscopy analysis(SEM-EDS),and thermogravimetric-differential thermogravimetric analysis(TG-DTG).The experimental results show that the density and strength of the material are significantly improved under the synergistic effect of fractal dimension and CO_(2)nanobubbles.When the fractal dimension reaches 2.65,the mass ratio of coarse and fine aggregates reaches the optimal balance,and the structural density is greatly improved at the same time.At this time,the uniaxial compressive strength and elastic modulus reach their peak values,with increases of up to 13.46%and 27.47%,respectively.CO_(2)nanobubbles enhance the material properties by promoting hydration reaction and carbonization.At the microscopic level,CO_(2)nanobubble water promotes the formation of C-S-H(hydrated calcium silicate),C-A-S-H(hydrated calcium aluminium silicate)gel and CaCO_(3),which is the main way to enhance the performance.Thermogravimetric studies have shown that when the fractal dimension is 2.65,the dehydration of hydration products and the decarbonization process of CaCO_(3)are most obvious,and CO_(2)nanobubble water promotes the carbonization reaction,making it surpass the natural state.The CO_(2)sequestration quality of cement-fly ash-based materials treated with CO_(2)nanobubble water at different fractal dimensions increased by 12.4wt%to 99.8wt%.The results not only provide scientific insights for the design and implementation of low-carbon filling materials,but also provide a solid theoretical basis for strengthening green mining practices and promoting sustainable resource utilization.展开更多
Magnesium is distinguished by its highly anisotropic inelastic deformation involving a profuse activity of deformation twinning.Instrumented micro/nano-indentation technique has been widely applied to characterize the...Magnesium is distinguished by its highly anisotropic inelastic deformation involving a profuse activity of deformation twinning.Instrumented micro/nano-indentation technique has been widely applied to characterize the mechanical properties of magnesium,typically through the analysis of the indentation load-depth response,surface topography,and less commonly,the post-mortem microstructure within the bulk material.However,experimental limitations prevent the real-time observation of the evolving microstructure.To bridge this gap,we employ a recently-developed finite-strain model that couples the phase-field method and conventional crystal plasticity to simulate the evolution of the indentation-induced twin microstructure and its interaction with plastic slip in a magnesium single-crystal.Particular emphasis is placed on two aspects:orientation-dependent inelastic deformation and indentation size effects.Several outcomes of our 2D computational study are consistent with prior experimental observations.Chief among them is the intricate morphology of twin microstructure obtained at large spatial scales,which,to our knowledge,represents a level of detail that has not been captured in previous modeling studies.To further elucidate on size effects,we extend the model by incorporating gradient-enhanced crystal plasticity,and re-examine the notion of‘smaller is stronger’.The corresponding results underscore the dominant influence of gradient plasticity over the interfacial energy of twin boundaries in governing the size-dependent mechanical response.展开更多
In this study, we use the Bohai Sea area as an example to investigate the characteristics of secondary microseisms and their impact on seismic noise based on the temporal frequency spectral analysis of observation dat...In this study, we use the Bohai Sea area as an example to investigate the characteristics of secondary microseisms and their impact on seismic noise based on the temporal frequency spectral analysis of observation data from 33 broadband seismic stations during strong gust periods, and new perspectives are proposed on the generation mechanisms of secondary microseisms. The results show that short-period double- frequency (SPDF) and long-period double-frequency (LPDF) microseisms exhibit significant alternating trends of strengthening and weakening in the northwest area of the Bohai Sea. SPDF microseisms are generated by irregular wind waves during strong off shore wind periods, with a broad frequency band distributed in the range of 0.2-1 Hz;LPDF microseisms are generated by regular swells during periods of sea wind weakening, with a narrow frequency band concentrated between 0.15 and 0.3 Hz. In terms of temporal dimensions, as the sea wind weakens, the energy of SPDF microseisms weakens, and the dominant frequencies increase, whereas the energy of LPDF microseisms strengthens and the dominant frequencies decrease, which is consistent with the process of the decay of wind waves and the growth of swells. In terms of spatial dimensions, as the microseisms propagate inland areas, the advantageous frequency band and energy of SPDF microseisms are reduced and significantly attenuated, respectively, whereas LPDF microseisms show no significant changes. And during the propagation process in high-elevation areas, LPDF microseisms exhibit a certain site amplifi cation eff ect when the energy is strong. The results provide important supplements to the basic theory of secondary microseisms, preliminarily reveal the relationship between the atmosphere, ocean, and seismic noise, and provide important theoretical references for conducting geological and oceanographic research based on the characteristics of secondary microseisms.展开更多
Butt welding of 0.2 mm-thick TiNi shape memory alloy sheet （SMA） was carried out using impulse laser, and tensile strength, fracture morphology, microstructure and phase change behaviour of welded joint were studied...Butt welding of 0.2 mm-thick TiNi shape memory alloy sheet （SMA） was carried out using impulse laser, and tensile strength, fracture morphology, microstructure and phase change behaviour of welded joint were studied. The results show that using impulse laser can realize good butt welding of TiNi SMA sheet, tensile strength of welded joint is 683 MPa, which achieves 97% of that of cold rolled base metal, and the fracture mode of welded joint is ductile type as well as base metal. The welded joint can be divided into four zones according to grain size and microstructure. The microstructures of welded seam center zone are fine equiaxed crystals and the microstructures of both lower surface and upper surface edge zones are columnar crystals. When welded joint is vacuum annealed after welding, the phase transformation process is basically similar to the annealed base metal.展开更多
Micro/nano hierarchical structures could endow materials with various surface functions.However,the multilayer and multiscale characteristics of micro/nano hierarchical structures bring difficulties for their one step...Micro/nano hierarchical structures could endow materials with various surface functions.However,the multilayer and multiscale characteristics of micro/nano hierarchical structures bring difficulties for their one step and controllable fabrication.Accordingly,based on tip-based fabrication techniques,this study proposed a micro-amplitude vibration-assisted scratching method by introducing a periodic backward displacement into the conventional scratching process,which enabled the synchronous creation of the microscale V-groove and nanoscale ripples,i.e.a typical micro/nano hierarchical structure.The experiments and finite element modeling were employed to explore the formation process and mechanism of the micro/nano hierarchical structures.Being different from conventional cutting,this method was mainly based on the plow mechanism,and it could accurately replicate the shape of the indenter on the material surface.The microscale V-groove was formed due to the scratching action,and the nanoscale ripple was formed due to the extrusion action of the indenter on the microscale V-groove’s surface.Furthermore,the relationships between the processing parameters and the dimensions of the micro/nano hierarchical structures were established through experiments,and optimized processing parameters were determined to achieve regular micro/nano hierarchical structures.By this method,complex patterns constructed by various micro/nano hierarchical structures were fabricated on both flat and curved surfaces,achieving diverse surface structural colors.展开更多
Semisolid ZL101 aluminum slurry was prepared by a micro fused-casting process.The nozzle temperature has great effects on the microstructure and mechanical properties,which are primarily influenced through changing co...Semisolid ZL101 aluminum slurry was prepared by a micro fused-casting process.The nozzle temperature has great effects on the microstructure and mechanical properties,which are primarily influenced through changing cooling conditions of the fused-casting area.With the decline of nozzle temperatures,the microstructure of semisolid ZL101 aluminum slurry tends to be more homogeneous,delivering smaller grains.Temperatures of liquids and solids were measured by differential scanning calorimetry(DSC).Distribution and characteristics of microstructure were examined by scanning electron microscopy(SEM)equipped with energy dispersive spectrometer(EDS)and optical microscope(OM).It is found that uniform shape and good grain size are observed for semisolid samples fabricated by micro fused-casting under conditions including nozzle temperature of 592℃,bucket temperature of 600℃,stirring velocity of 600 r/min and channel diameter of 3 mm.Due to the smaller average grain size of 53μm and shape factor of 0.71 for the fine grains,the ultrahigh average tensile strength and Vickers hardness can reach(181±1.25)MPa and(87.95±1.18)HV for the optimized semisolid ZL101 aluminum slurry,respectively.展开更多
Nowadays,wireless communication devices turn out to be transportable owing to the execution of the current technologies.The antenna is the most important component deployed for communication purposes.The antenna plays...Nowadays,wireless communication devices turn out to be transportable owing to the execution of the current technologies.The antenna is the most important component deployed for communication purposes.The antenna plays an imperative role in receiving and transmitting the signals for any sensor network.Among varied antennas,micro strip fractal antenna(MFA)significantly contributes to increasing antenna gain.This study employs a hybrid optimization method known as the elephant clan updated grey wolf algorithm to introduce an optimized MFA design.This method optimizes antenna characteristics,including directivity and gain.Here,the factors,including length,width,ground plane length,height,and feed offset-X and feed offset-Y,are taken into account to achieve the best performance of gain and directivity.Ultimately,the superiority of the suggested technique over state-of-the-art strategies is calculated for various metrics such as cost and gain.The adopted model converges to a minimal value of 0.2872.Further,the spider monkey optimization(SMO)model accomplishes the worst performance over all other existing models like elephant herding optimization(EHO),grey wolf optimization(GWO),lion algorithm(LA),support vector regressor(SVR),bacterial foraging-particle swarm optimization(BF-PSO)and shark smell optimization(SSO).Effective MFA design is obtained using the suggested strategy regarding various parameters.展开更多
Evaluating the seismic site effect by the ambient noise based horizontal-to-vertical spectral ratio(HVSR)method is strongly affected by the spatial and temporal variations of the ambient noise sources.Therefore,it is ...Evaluating the seismic site effect by the ambient noise based horizontal-to-vertical spectral ratio(HVSR)method is strongly affected by the spatial and temporal variations of the ambient noise sources.Therefore,it is necessary to locate the source regions of ambient noise and investigate the relationships between the source energy and HVSR values at the predominant frequency(HVSRf_(0))of the site.The generation mechanisms of the single-and double-frequency microseisms(SFMs,0.05-0.085 Hz and DFMs,0.1-0.5 Hz)in ambient noise are better understood than the noise in other frequency bands and they are dominantly composed of fundamental Rayleigh(Rg)waves.With this advantage,the recordings of SFMs and DFMs at 30 stations in the east coast region of the United States are used to demonstrate a study on locating their source regions with reasonable certainty and constructing the functional relationship between the HVSRf_(0) and the source energy of SFMs and DFMs.The recordings are processed in four sub-frequency bands(Fs)of SF and DF bands and a polarization analysis is carried out to select the ellipsoids approximating the particle motions of Rg waves.Then the probability density functions of the back azimuths of the ellipsoids’semi-major axes are computed for each F and station,and are projected on the ocean to determine their possible source regions.These regions are further constrained by(1)the correlation coefficients between the SFMs and the WAVEWATCHⅢ(WWⅢ)hindcasts of ocean wave spectra in the SF band,or between the DFMs and the modeled DF energy on ocean surface in the selected time windows in the DF band,(2)the energy contribution defined by(i)the average WWⅢocean wave energy and the ocean bottom topographical gradient in the SF band,or(ii)the average modeled DF energy on ocean surface and a frequency and water depth dependent coefficient measuring the conversion efficiency of DF energy from water to solid earth in the DF band,and(3)the percentile retained energy of Rg waves in both the SF and DF bands.Results of source regions reveal that(1)the SFMs recorded in eastern US result from the interactions of low frequency(0.05-0.085 Hz)ocean waves with the continental slope and shelf of western North Atlantic Ocean;(2)the source regions for long-(0.1-0.2 Hz)period DFMs are located in the deep ocean close to the continental slope;and(3)the short-(0.2–0.5 Hz)period DFMs are generated in the continental shelf.Finally,the correlation analyses between the simulated source energy and the HVSRf_(0) values at the stations whose f_(0) s fall in DF band are carried out revealing significant source effect on thick sediments at low frequencies.展开更多
Ever since the impoundment of Three Gorges Reservoir（TGR）, the seismicity in head region of TGR has increased significantly. Coupled with wide fluctuation of water level each year, it becomes more important to study...Ever since the impoundment of Three Gorges Reservoir（TGR）, the seismicity in head region of TGR has increased significantly. Coupled with wide fluctuation of water level each year, it becomes more important to study the deformation forecasting of landslides beside TGR. As a famous active landslide beside TGR, Huangtupo riverside landslide is selected for a case study. Based on long term water level fluctuation and seismic monitoring, three typical adverse conditions are determined. With the established 3D numerical landslide model, seepage-dynamic coupling calculation is conducted under the seismic intensity of V degree. Results are as follows： 1. the dynamic water pressure formed by water level fluctuation will intensify the deformation of landslide; 2. under seismic load, the dynamic hysteresis is significant in defective geological bodies, such as weak layer and slip zone soil, because of much higher damping ratios, the seismic accelerate would be amplified in these elements; 3. microseisms are not intense enough to cause the landslide instability suddenly, but long term deformation accumulation effect of landslide should be paid more attention; 4. in numerical simulation, the factors of unbalance force and excess pore pressure also can be used in forecasting deformation tendency of landslide.展开更多
CeO2 nanoparticles(nano-CeO2p) were added into laser cladded NiCoCrAlY coatings on Ni-based superalloy substrate to improve the microstructure and properties.Scanning electron microscope(SEM),X-ray diffractometer(XRD)...CeO2 nanoparticles(nano-CeO2p) were added into laser cladded NiCoCrAlY coatings on Ni-based superalloy substrate to improve the microstructure and properties.Scanning electron microscope(SEM),X-ray diffractometer(XRD),micro-hardness tester,and heat treatment furnace were employed to investigate their morphologies,phases,micro-hardness and thermal shock resistance,compared with the coating without nanoparticles added.The results showed that the microstructure and properties of the coatings with the addition ...展开更多
To obtain a kind of convenient oral dosage form of protein, which can be fully absorbed and is efficient and safe, the thymosin-loaded PLA（polylactic acid） microspheres are prepared by the emulsification- solvent ev...To obtain a kind of convenient oral dosage form of protein, which can be fully absorbed and is efficient and safe, the thymosin-loaded PLA（polylactic acid） microspheres are prepared by the emulsification- solvent evaporation method and the orthogonal design is used to optimize the technology of preparation. The form of the medicament microspheres of thymosin are proved by differential thermal analysis （DTA）. The drug content is determined by the Lowry method, and the package ratio of medicament microspheres of thymosin and drug release in vitro are calculated. The results show that the average diameter and encapsulation efficiency of the product prepared according to the optimized formulation are 13. 8 μm and 80. 7%, respectively. The in vitro release behavior within 12 h can be described by the Higuchi equation with T1/2 = 295 rain. There are no significant changes in size distribution and residual drug contents after being stored at 25℃ and 40 ℃ for 90 d, respectively. Due to the fact that its thymosin content and package ratio meet the requirement, and its releasing half life is long, the thymosin-loaded PLA microsohere has a favorable application future.展开更多
[ Objective] Correlation of microstructure of leaf sheath epidermis and nutrient composition of palm plants with the damage degree of red palm fiber elephant in four kinds of plants in Nanning were analyzed in order t...[ Objective] Correlation of microstructure of leaf sheath epidermis and nutrient composition of palm plants with the damage degree of red palm fiber elephant in four kinds of plants in Nanning were analyzed in order to control the occurrence and damage of this insect in Nanning. [Method] Taken 4 kinds of Palmae plants in Nanning including Ravenea fivulafis, Washingtonia filifera, Phoenix canafiensis, Roystonea regia （HBK.）O. F. Cook as materials, damage situation of the red palm fiber elephant was investigated, microstructure of leaf sheath epidermis and nutrient composition of palm plants were analyzed and determined. [ Result] The results showed that there was direct correlation between the microstructure of leaf sheath epidermis and nutrient composition with the physical resistance of palm plant against red palm fiber elephant. The extend of damage from red palm fiber elephant had negatively relation with the thickness of corneum and leaf epidermis. The damage degree caused by red palm fiber elephant increased with the content of crude protein, crude ash and nitrogen free extract increasing, also increased with the content of rude fiber decreasing. [Condusion] The damage degree of red palm fiber elephant had a relationship with microstructure of leaf sheath epidermis and nutrient composition of palm plants.展开更多
Shake table testing was performed to investigate the dynamic stability of a mid-dip bedding rock slope under frequent earthquakes. Then, numerical modelling was established to further study the slope dynamic stability...Shake table testing was performed to investigate the dynamic stability of a mid-dip bedding rock slope under frequent earthquakes. Then, numerical modelling was established to further study the slope dynamic stability under purely microseisms and the influence of five factors, including seismic amplitude, slope height, slope angle, strata inclination and strata thickness, were considered. The experimental results show that the natural frequency of the slope decreases and damping ratio increases as the earthquake loading times increase. The dynamic strength reduction method is adopted for the stability evaluation of the bedding rock slope in numerical simulation, and the slope stability decreases with the increase of seismic amplitude, increase of slope height, reduction of strata thickness and increase of slope angle. The failure mode of a mid-dip bedding rock slope in the shaking table test is integral slipping along the bedding surface with dipping tensile cracks at the slope rear edge going through the bedding surfaces. In the numerical simulation, the long-term stability of a mid-dip bedding slope is worst under frequent microseisms and the slope is at risk of integral sliding instability, whereas the slope rock mass is more broken than shown in the shaking table test. The research results are of practical significance to better understand the formation mechanism of reservoir landslides and prevent future landslide disasters.展开更多
Mge3Lie0.4Zr alloys containing RE elements(Gd,La,Nd)(Mge3LieREe0.4Zr alloys)are investigated to reveal the influence of homogenization treatment on microstructures and distributions of RE,Zr elements.It is found that...Mge3Lie0.4Zr alloys containing RE elements(Gd,La,Nd)(Mge3LieREe0.4Zr alloys)are investigated to reveal the influence of homogenization treatment on microstructures and distributions of RE,Zr elements.It is found that 300C24 h homogenization treatment shows better improvement on the microstructure including the refinement of grain size,the dispersion of cellular dendrite and low melting point particles.Before treatment,La and Nd segregate effectively at grain boundary and Zr segregates in the form of precipitates.Homogenization treatment induces the reduction of RE segregation.However,the segregation of Zr in precipitates cannot be abated due to the relatively low diffusion rate compared with RE elements.展开更多
The isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 ℃ in 50 ℃ intervals,with strain rate of 0.001-1.000 s-1and height reduction of 20%-60%.The e...The isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 ℃ in 50 ℃ intervals,with strain rate of 0.001-1.000 s-1and height reduction of 20%-60%.The effect of processing parameters（deformation temperature,strain rate and deformation degree） on the microstructure evolution and the microstructure variables was investigated.The results show that the content of primary α phase decreases with the increase in deformation temperature.The effect of strain rate on microstructure variables of isothermally compressed Ti555211 alloy is mainly dependent on the deformation temperature.The fine second α phase partly transforms to β phase due to the deformation heat effect at the high strain rate,α phase becomes globular with temperature increasing and strain rate decreasing.In contrast,α phase is refined with temperature decreasing and strain rate increasing.The deformation degree has a little influence on the grain size and the morphology of primary α phase,but the effect of deformation degree on the morphology of second α phase is significant.The larger deformation degree is in favor of the globularization of lamellar α structure.展开更多
Laser micro cladding deposition manufacturing(Ll CDM) is a newly developed rapid manufacturing method for metals.The Ll CDM technology adopts a novel powder feeding method based on alternating friction and inertia for...Laser micro cladding deposition manufacturing(Ll CDM) is a newly developed rapid manufacturing method for metals.The Ll CDM technology adopts a novel powder feeding method based on alternating friction and inertia force, and this powder feeding method can effectively improve the accuracy and orientation of the powder injection, resulting in a smaller molten pool size and a higher cooling rate of liquid metal.Therefore, the components fabricated by Ll CDM could obtain the finer microstructures and the improved mechanical properties.It is found that the components fabricated by Ll CDM are fully dense free of cracks or pores and exhibit columnar prior b grains with a finer acicular a0 phase microstructure.The microhardness(HV0.2) of the thin-wall component is HV 400–HV 500 in the majority part of the cross section and can reach about HV 850 in the top region.The ultimate tensile strength(UTS) and elongation show insignificant dependence on the testing directions of the tensilespecimens.The UTS is between 1,002 and 1,100 MPa, and the elongation is between 10.0 % and 14.7 %.展开更多
A wet-chemical method was presented for preparation of spherical, flowerlike, hexagonal, and triangular microsized silver crystals. Well-defined particles were prepared by mixing of iron（II） sulfate heptahydrate sol...A wet-chemical method was presented for preparation of spherical, flowerlike, hexagonal, and triangular microsized silver crystals. Well-defined particles were prepared by mixing of iron（II） sulfate heptahydrate solution with silver nitrate solution at the presence of different modifiers with high-speed stirring at 8-20℃. It is found that the diameters of resulting products are 0.6-6.0 um and the morphologies of the silver microcrystals are greatly affected by the introduced modifiers. It is concluded that the microsized silver crystals with different morphologies can be synthesized by introducing appropriate modifiers at appropriate experimental parameters. Scanning electron microscopy and X-ray diffraction were used to characterize the resulting products.展开更多
基金financially supported by the China Scholarship Council(CSC)。
文摘Mine filling materials urgently need to improve mechanical properties and achieve low-carbon transformation.This study explores the mechanism of the synergistic effect of optimizing aggregate fractal grading and introducing CO_(2)nanobubble technology to improve the performance of cement-fly ash-based backfill materials(CFB).The properties including fluidity,setting time,uniaxial compressive strength,elastic modulus,porosity,microstructure and CO_(2)storage performance were systematically studied through methods such as fluidity evaluation,time test,uniaxial compression test,mercury intrusion porosimetry(MIP),scanning electron microscopy-energy dispersive spectroscopy analysis(SEM-EDS),and thermogravimetric-differential thermogravimetric analysis(TG-DTG).The experimental results show that the density and strength of the material are significantly improved under the synergistic effect of fractal dimension and CO_(2)nanobubbles.When the fractal dimension reaches 2.65,the mass ratio of coarse and fine aggregates reaches the optimal balance,and the structural density is greatly improved at the same time.At this time,the uniaxial compressive strength and elastic modulus reach their peak values,with increases of up to 13.46%and 27.47%,respectively.CO_(2)nanobubbles enhance the material properties by promoting hydration reaction and carbonization.At the microscopic level,CO_(2)nanobubble water promotes the formation of C-S-H(hydrated calcium silicate),C-A-S-H(hydrated calcium aluminium silicate)gel and CaCO_(3),which is the main way to enhance the performance.Thermogravimetric studies have shown that when the fractal dimension is 2.65,the dehydration of hydration products and the decarbonization process of CaCO_(3)are most obvious,and CO_(2)nanobubble water promotes the carbonization reaction,making it surpass the natural state.The CO_(2)sequestration quality of cement-fly ash-based materials treated with CO_(2)nanobubble water at different fractal dimensions increased by 12.4wt%to 99.8wt%.The results not only provide scientific insights for the design and implementation of low-carbon filling materials,but also provide a solid theoretical basis for strengthening green mining practices and promoting sustainable resource utilization.
文摘Magnesium is distinguished by its highly anisotropic inelastic deformation involving a profuse activity of deformation twinning.Instrumented micro/nano-indentation technique has been widely applied to characterize the mechanical properties of magnesium,typically through the analysis of the indentation load-depth response,surface topography,and less commonly,the post-mortem microstructure within the bulk material.However,experimental limitations prevent the real-time observation of the evolving microstructure.To bridge this gap,we employ a recently-developed finite-strain model that couples the phase-field method and conventional crystal plasticity to simulate the evolution of the indentation-induced twin microstructure and its interaction with plastic slip in a magnesium single-crystal.Particular emphasis is placed on two aspects:orientation-dependent inelastic deformation and indentation size effects.Several outcomes of our 2D computational study are consistent with prior experimental observations.Chief among them is the intricate morphology of twin microstructure obtained at large spatial scales,which,to our knowledge,represents a level of detail that has not been captured in previous modeling studies.To further elucidate on size effects,we extend the model by incorporating gradient-enhanced crystal plasticity,and re-examine the notion of‘smaller is stronger’.The corresponding results underscore the dominant influence of gradient plasticity over the interfacial energy of twin boundaries in governing the size-dependent mechanical response.
基金supported by Earthquake Science and Technology Spark Program of China Earthquake Administration (No. XH20006Y)Local Standards Formulation and Revision Program of Hebei Province (No. FW202154)+1 种基金Earthquake Science and Technology Spark Program of Hebei Earthquake Agency (No. DZ2024112100002)2023 Seismological Data Sharing Project of China Earthquake Networks Center (Dataset Project)。
文摘In this study, we use the Bohai Sea area as an example to investigate the characteristics of secondary microseisms and their impact on seismic noise based on the temporal frequency spectral analysis of observation data from 33 broadband seismic stations during strong gust periods, and new perspectives are proposed on the generation mechanisms of secondary microseisms. The results show that short-period double- frequency (SPDF) and long-period double-frequency (LPDF) microseisms exhibit significant alternating trends of strengthening and weakening in the northwest area of the Bohai Sea. SPDF microseisms are generated by irregular wind waves during strong off shore wind periods, with a broad frequency band distributed in the range of 0.2-1 Hz;LPDF microseisms are generated by regular swells during periods of sea wind weakening, with a narrow frequency band concentrated between 0.15 and 0.3 Hz. In terms of temporal dimensions, as the sea wind weakens, the energy of SPDF microseisms weakens, and the dominant frequencies increase, whereas the energy of LPDF microseisms strengthens and the dominant frequencies decrease, which is consistent with the process of the decay of wind waves and the growth of swells. In terms of spatial dimensions, as the microseisms propagate inland areas, the advantageous frequency band and energy of SPDF microseisms are reduced and significantly attenuated, respectively, whereas LPDF microseisms show no significant changes. And during the propagation process in high-elevation areas, LPDF microseisms exhibit a certain site amplifi cation eff ect when the energy is strong. The results provide important supplements to the basic theory of secondary microseisms, preliminarily reveal the relationship between the atmosphere, ocean, and seismic noise, and provide important theoretical references for conducting geological and oceanographic research based on the characteristics of secondary microseisms.
基金Project(200804)supported by State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology,China
文摘Butt welding of 0.2 mm-thick TiNi shape memory alloy sheet （SMA） was carried out using impulse laser, and tensile strength, fracture morphology, microstructure and phase change behaviour of welded joint were studied. The results show that using impulse laser can realize good butt welding of TiNi SMA sheet, tensile strength of welded joint is 683 MPa, which achieves 97% of that of cold rolled base metal, and the fracture mode of welded joint is ductile type as well as base metal. The welded joint can be divided into four zones according to grain size and microstructure. The microstructures of welded seam center zone are fine equiaxed crystals and the microstructures of both lower surface and upper surface edge zones are columnar crystals. When welded joint is vacuum annealed after welding, the phase transformation process is basically similar to the annealed base metal.
基金supported by the Jilin Province Key Research and Development Plan Project(20240302066GX)the National Natural Science Foundation of China(Grant No.52075221)the Fundamental Research Funds for the Central Universities(2023-JCXK-02)。
文摘Micro/nano hierarchical structures could endow materials with various surface functions.However,the multilayer and multiscale characteristics of micro/nano hierarchical structures bring difficulties for their one step and controllable fabrication.Accordingly,based on tip-based fabrication techniques,this study proposed a micro-amplitude vibration-assisted scratching method by introducing a periodic backward displacement into the conventional scratching process,which enabled the synchronous creation of the microscale V-groove and nanoscale ripples,i.e.a typical micro/nano hierarchical structure.The experiments and finite element modeling were employed to explore the formation process and mechanism of the micro/nano hierarchical structures.Being different from conventional cutting,this method was mainly based on the plow mechanism,and it could accurately replicate the shape of the indenter on the material surface.The microscale V-groove was formed due to the scratching action,and the nanoscale ripple was formed due to the extrusion action of the indenter on the microscale V-groove’s surface.Furthermore,the relationships between the processing parameters and the dimensions of the micro/nano hierarchical structures were established through experiments,and optimized processing parameters were determined to achieve regular micro/nano hierarchical structures.By this method,complex patterns constructed by various micro/nano hierarchical structures were fabricated on both flat and curved surfaces,achieving diverse surface structural colors.
基金Funded by the Natural Science Foundation of Henan Province(No.252300420256)。
文摘Semisolid ZL101 aluminum slurry was prepared by a micro fused-casting process.The nozzle temperature has great effects on the microstructure and mechanical properties,which are primarily influenced through changing cooling conditions of the fused-casting area.With the decline of nozzle temperatures,the microstructure of semisolid ZL101 aluminum slurry tends to be more homogeneous,delivering smaller grains.Temperatures of liquids and solids were measured by differential scanning calorimetry(DSC).Distribution and characteristics of microstructure were examined by scanning electron microscopy(SEM)equipped with energy dispersive spectrometer(EDS)and optical microscope(OM).It is found that uniform shape and good grain size are observed for semisolid samples fabricated by micro fused-casting under conditions including nozzle temperature of 592℃,bucket temperature of 600℃,stirring velocity of 600 r/min and channel diameter of 3 mm.Due to the smaller average grain size of 53μm and shape factor of 0.71 for the fine grains,the ultrahigh average tensile strength and Vickers hardness can reach(181±1.25)MPa and(87.95±1.18)HV for the optimized semisolid ZL101 aluminum slurry,respectively.
文摘Nowadays,wireless communication devices turn out to be transportable owing to the execution of the current technologies.The antenna is the most important component deployed for communication purposes.The antenna plays an imperative role in receiving and transmitting the signals for any sensor network.Among varied antennas,micro strip fractal antenna(MFA)significantly contributes to increasing antenna gain.This study employs a hybrid optimization method known as the elephant clan updated grey wolf algorithm to introduce an optimized MFA design.This method optimizes antenna characteristics,including directivity and gain.Here,the factors,including length,width,ground plane length,height,and feed offset-X and feed offset-Y,are taken into account to achieve the best performance of gain and directivity.Ultimately,the superiority of the suggested technique over state-of-the-art strategies is calculated for various metrics such as cost and gain.The adopted model converges to a minimal value of 0.2872.Further,the spider monkey optimization(SMO)model accomplishes the worst performance over all other existing models like elephant herding optimization(EHO),grey wolf optimization(GWO),lion algorithm(LA),support vector regressor(SVR),bacterial foraging-particle swarm optimization(BF-PSO)and shark smell optimization(SSO).Effective MFA design is obtained using the suggested strategy regarding various parameters.
文摘Evaluating the seismic site effect by the ambient noise based horizontal-to-vertical spectral ratio(HVSR)method is strongly affected by the spatial and temporal variations of the ambient noise sources.Therefore,it is necessary to locate the source regions of ambient noise and investigate the relationships between the source energy and HVSR values at the predominant frequency(HVSRf_(0))of the site.The generation mechanisms of the single-and double-frequency microseisms(SFMs,0.05-0.085 Hz and DFMs,0.1-0.5 Hz)in ambient noise are better understood than the noise in other frequency bands and they are dominantly composed of fundamental Rayleigh(Rg)waves.With this advantage,the recordings of SFMs and DFMs at 30 stations in the east coast region of the United States are used to demonstrate a study on locating their source regions with reasonable certainty and constructing the functional relationship between the HVSRf_(0) and the source energy of SFMs and DFMs.The recordings are processed in four sub-frequency bands(Fs)of SF and DF bands and a polarization analysis is carried out to select the ellipsoids approximating the particle motions of Rg waves.Then the probability density functions of the back azimuths of the ellipsoids’semi-major axes are computed for each F and station,and are projected on the ocean to determine their possible source regions.These regions are further constrained by(1)the correlation coefficients between the SFMs and the WAVEWATCHⅢ(WWⅢ)hindcasts of ocean wave spectra in the SF band,or between the DFMs and the modeled DF energy on ocean surface in the selected time windows in the DF band,(2)the energy contribution defined by(i)the average WWⅢocean wave energy and the ocean bottom topographical gradient in the SF band,or(ii)the average modeled DF energy on ocean surface and a frequency and water depth dependent coefficient measuring the conversion efficiency of DF energy from water to solid earth in the DF band,and(3)the percentile retained energy of Rg waves in both the SF and DF bands.Results of source regions reveal that(1)the SFMs recorded in eastern US result from the interactions of low frequency(0.05-0.085 Hz)ocean waves with the continental slope and shelf of western North Atlantic Ocean;(2)the source regions for long-(0.1-0.2 Hz)period DFMs are located in the deep ocean close to the continental slope;and(3)the short-(0.2–0.5 Hz)period DFMs are generated in the continental shelf.Finally,the correlation analyses between the simulated source energy and the HVSRf_(0) values at the stations whose f_(0) s fall in DF band are carried out revealing significant source effect on thick sediments at low frequencies.
基金financially supported by the National Natural Science Foundation of China (Nos. 51409011 and 51309029)the Basic Scientific Research Operating Expenses of Central-Level Public Academies and Institutes (Nos. CKSF2014057/YT and CKSF2015051/YT)
文摘Ever since the impoundment of Three Gorges Reservoir（TGR）, the seismicity in head region of TGR has increased significantly. Coupled with wide fluctuation of water level each year, it becomes more important to study the deformation forecasting of landslides beside TGR. As a famous active landslide beside TGR, Huangtupo riverside landslide is selected for a case study. Based on long term water level fluctuation and seismic monitoring, three typical adverse conditions are determined. With the established 3D numerical landslide model, seepage-dynamic coupling calculation is conducted under the seismic intensity of V degree. Results are as follows： 1. the dynamic water pressure formed by water level fluctuation will intensify the deformation of landslide; 2. under seismic load, the dynamic hysteresis is significant in defective geological bodies, such as weak layer and slip zone soil, because of much higher damping ratios, the seismic accelerate would be amplified in these elements; 3. microseisms are not intense enough to cause the landslide instability suddenly, but long term deformation accumulation effect of landslide should be paid more attention; 4. in numerical simulation, the factors of unbalance force and excess pore pressure also can be used in forecasting deformation tendency of landslide.
基金supported by the Doctoral Program of Higher Education of China (20060287019)the Opening Research Fund of Jiangsu Key Laboratory of Tribology of China (kjsmcx07001)Graduate Innovation Foundation of Jiangsu Province of China (CX08B-039Z)
文摘CeO2 nanoparticles(nano-CeO2p) were added into laser cladded NiCoCrAlY coatings on Ni-based superalloy substrate to improve the microstructure and properties.Scanning electron microscope(SEM),X-ray diffractometer(XRD),micro-hardness tester,and heat treatment furnace were employed to investigate their morphologies,phases,micro-hardness and thermal shock resistance,compared with the coating without nanoparticles added.The results showed that the microstructure and properties of the coatings with the addition ...
文摘To obtain a kind of convenient oral dosage form of protein, which can be fully absorbed and is efficient and safe, the thymosin-loaded PLA（polylactic acid） microspheres are prepared by the emulsification- solvent evaporation method and the orthogonal design is used to optimize the technology of preparation. The form of the medicament microspheres of thymosin are proved by differential thermal analysis （DTA）. The drug content is determined by the Lowry method, and the package ratio of medicament microspheres of thymosin and drug release in vitro are calculated. The results show that the average diameter and encapsulation efficiency of the product prepared according to the optimized formulation are 13. 8 μm and 80. 7%, respectively. The in vitro release behavior within 12 h can be described by the Higuchi equation with T1/2 = 295 rain. There are no significant changes in size distribution and residual drug contents after being stored at 25℃ and 40 ℃ for 90 d, respectively. Due to the fact that its thymosin content and package ratio meet the requirement, and its releasing half life is long, the thymosin-loaded PLA microsohere has a favorable application future.
基金Supported by Guangxi Agricultural College Science Topics(B070206)~~
文摘[ Objective] Correlation of microstructure of leaf sheath epidermis and nutrient composition of palm plants with the damage degree of red palm fiber elephant in four kinds of plants in Nanning were analyzed in order to control the occurrence and damage of this insect in Nanning. [Method] Taken 4 kinds of Palmae plants in Nanning including Ravenea fivulafis, Washingtonia filifera, Phoenix canafiensis, Roystonea regia （HBK.）O. F. Cook as materials, damage situation of the red palm fiber elephant was investigated, microstructure of leaf sheath epidermis and nutrient composition of palm plants were analyzed and determined. [ Result] The results showed that there was direct correlation between the microstructure of leaf sheath epidermis and nutrient composition with the physical resistance of palm plant against red palm fiber elephant. The extend of damage from red palm fiber elephant had negatively relation with the thickness of corneum and leaf epidermis. The damage degree caused by red palm fiber elephant increased with the content of crude protein, crude ash and nitrogen free extract increasing, also increased with the content of rude fiber decreasing. [Condusion] The damage degree of red palm fiber elephant had a relationship with microstructure of leaf sheath epidermis and nutrient composition of palm plants.
基金National Natural Science Foundation of China under Grant No. 41372356the College Cultivation Project of the National Natural Science Foundation of China under Grant No. 2018PY30+1 种基金the Basic Research and Frontier Exploration Project of Chongqing,China under Grant No. cstc2018jcyj A1597the Graduate Scientific Research and Innovation Foundation of Chongqing,China under Grant No. CYS18026。
文摘Shake table testing was performed to investigate the dynamic stability of a mid-dip bedding rock slope under frequent earthquakes. Then, numerical modelling was established to further study the slope dynamic stability under purely microseisms and the influence of five factors, including seismic amplitude, slope height, slope angle, strata inclination and strata thickness, were considered. The experimental results show that the natural frequency of the slope decreases and damping ratio increases as the earthquake loading times increase. The dynamic strength reduction method is adopted for the stability evaluation of the bedding rock slope in numerical simulation, and the slope stability decreases with the increase of seismic amplitude, increase of slope height, reduction of strata thickness and increase of slope angle. The failure mode of a mid-dip bedding rock slope in the shaking table test is integral slipping along the bedding surface with dipping tensile cracks at the slope rear edge going through the bedding surfaces. In the numerical simulation, the long-term stability of a mid-dip bedding slope is worst under frequent microseisms and the slope is at risk of integral sliding instability, whereas the slope rock mass is more broken than shown in the shaking table test. The research results are of practical significance to better understand the formation mechanism of reservoir landslides and prevent future landslide disasters.
基金This work was supported by the Major State Basic Research Development Program of China(No.2013CB632203)National Key Technology R&D Program of China(2011BAE22B03)+3 种基金(2012BAF09B01)National Natural Science Foundation of China(51074207)Chinese Postdoctoral Science Foundation(2012M520634)the Fundamental Research Foundation of Central Universities(Grant Nos.N120509002 and N120309003).
文摘Mge3Lie0.4Zr alloys containing RE elements(Gd,La,Nd)(Mge3LieREe0.4Zr alloys)are investigated to reveal the influence of homogenization treatment on microstructures and distributions of RE,Zr elements.It is found that 300C24 h homogenization treatment shows better improvement on the microstructure including the refinement of grain size,the dispersion of cellular dendrite and low melting point particles.Before treatment,La and Nd segregate effectively at grain boundary and Zr segregates in the form of precipitates.Homogenization treatment induces the reduction of RE segregation.However,the segregation of Zr in precipitates cannot be abated due to the relatively low diffusion rate compared with RE elements.
基金financially supported by the Project of Introducing Talents of Discipline to Universities (‘‘111’’ Project) (No. B08040)
文摘The isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 ℃ in 50 ℃ intervals,with strain rate of 0.001-1.000 s-1and height reduction of 20%-60%.The effect of processing parameters（deformation temperature,strain rate and deformation degree） on the microstructure evolution and the microstructure variables was investigated.The results show that the content of primary α phase decreases with the increase in deformation temperature.The effect of strain rate on microstructure variables of isothermally compressed Ti555211 alloy is mainly dependent on the deformation temperature.The fine second α phase partly transforms to β phase due to the deformation heat effect at the high strain rate,α phase becomes globular with temperature increasing and strain rate decreasing.In contrast,α phase is refined with temperature decreasing and strain rate increasing.The deformation degree has a little influence on the grain size and the morphology of primary α phase,but the effect of deformation degree on the morphology of second α phase is significant.The larger deformation degree is in favor of the globularization of lamellar α structure.
基金financially supported by the National Natural Science Foundation of China (No. 50975152)
文摘Laser micro cladding deposition manufacturing(Ll CDM) is a newly developed rapid manufacturing method for metals.The Ll CDM technology adopts a novel powder feeding method based on alternating friction and inertia force, and this powder feeding method can effectively improve the accuracy and orientation of the powder injection, resulting in a smaller molten pool size and a higher cooling rate of liquid metal.Therefore, the components fabricated by Ll CDM could obtain the finer microstructures and the improved mechanical properties.It is found that the components fabricated by Ll CDM are fully dense free of cracks or pores and exhibit columnar prior b grains with a finer acicular a0 phase microstructure.The microhardness(HV0.2) of the thin-wall component is HV 400–HV 500 in the majority part of the cross section and can reach about HV 850 in the top region.The ultimate tensile strength(UTS) and elongation show insignificant dependence on the testing directions of the tensilespecimens.The UTS is between 1,002 and 1,100 MPa, and the elongation is between 10.0 % and 14.7 %.
文摘A wet-chemical method was presented for preparation of spherical, flowerlike, hexagonal, and triangular microsized silver crystals. Well-defined particles were prepared by mixing of iron（II） sulfate heptahydrate solution with silver nitrate solution at the presence of different modifiers with high-speed stirring at 8-20℃. It is found that the diameters of resulting products are 0.6-6.0 um and the morphologies of the silver microcrystals are greatly affected by the introduced modifiers. It is concluded that the microsized silver crystals with different morphologies can be synthesized by introducing appropriate modifiers at appropriate experimental parameters. Scanning electron microscopy and X-ray diffraction were used to characterize the resulting products.
