Three types of rock specimens, three-point bending specimen, anti-symmetric four-point bending specimen and direct shearing specimen, were used to achieve Mode I, Mode II and mixed mode I–II fracture, respectively. M...Three types of rock specimens, three-point bending specimen, anti-symmetric four-point bending specimen and direct shearing specimen, were used to achieve Mode I, Mode II and mixed mode I–II fracture, respectively. Microscopic characteristics of the three fracture modes of brittle rock were studied by SEM technique in order to analyze fracture behaviors and better understand fracture mechanisms of different fracture modes of brittle rock. Test results show that the microscopic characteristics of different fracture modes correspond to different fracture mechanisms. The surface of Mode I fracture has a great number of sparse and steep slip-steps with few tearing ridges and shows strong brittleness. In the surface of Mode II fracture there exist many tearing ridges and densely distributed parallel slip-steps and it is attributed to the action of shear stress. The co-action of tensile and shear stresses results in brittle cleavage planes mixed with streamline patterns and tearing ridges in the surface of mixed mode I–II fracture. The measured Mode II fracture toughness K II C and mixed mode I–II fracture toughness K mC are larger than Mode I fracture toughness K I C · K II C is about 3.5 times K I C, and KmC is about 1.2 times K I C.展开更多
2-Acrylamido-2-methyl-1-propanesulfonic acid （AMPS）, and maleic acid （MA） copolymerized with different feed ratios using N,N-dimethylformamide as a solvent and benzoyl peroxide （Bz2O2） as an initiator at 70℃. S...2-Acrylamido-2-methyl-1-propanesulfonic acid （AMPS）, and maleic acid （MA） copolymerized with different feed ratios using N,N-dimethylformamide as a solvent and benzoyl peroxide （Bz2O2） as an initiator at 70℃. Structure and composition of copolymers for a wide range of monomer feed were determined by elemental analysis （content of N for AMPS-units）. Monomer reactivity ratios for AMPS （M1）-MA （M2） pair were determined by the application of conventional linearization methods such as Fineman-Ross （F-R）, Kelen-Tudos（KT） and Extended Kelen-Tudos （EKT） and a nonlinear error invariable model method using a computer program RREVM. The characterizations were done by Fourier transform infrared spectroscopy （FTIR）, differential scanning calorimetry （DSC） thermal gravimetry analysis （TGA）, and and X-ray diffraction. The antimicrobial effects of polymers were also tested on various bacteria, and yeast.展开更多
In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosi...In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.展开更多
Nanostructured multiphase zirconia films （MZFs） are deposited on Zr substrate by the irradiation of energetic oxygen ions emanated from a plasma focus device. The oxygen operating gas pressure of 1 mbar （1 bar=105...Nanostructured multiphase zirconia films （MZFs） are deposited on Zr substrate by the irradiation of energetic oxygen ions emanated from a plasma focus device. The oxygen operating gas pressure of 1 mbar （1 bar=105 Pa） provides the most appropriate ion energy flux to deposit crystalline ZrO2 films. X-ray diffraction （XRD） patterns reveal the formation of polycrystalline ZrO2 films. The crystallite size （CS）, crystal growth, and dislocation densities are attributed to increasing focus shots, sample axial distances, and working gas pressures. Phase and orientation transformations from t-ZrO2 to m-ZrO2 and c-ZrO2 are associated with increasing focus shots and continuous annealing. For lower （200 ℃） annealing temperature （AT）, full width at half maximum （FWHM） of diffraction peak, CS, and dislocation density （δ） for （020） plane are found to be 0.494, 16.6 nm, and 3.63×10-3 nm-2 while for higher （400 ℃） AT, these parameters for （111） plane are found to be 0.388, 20.87 nm, and 2.29×10-3 nm-2, respectively. Scanning electron microscope （SEM） results demonstrate the formation of rounded grains with uniform distribution. The estimated values of atomic ratio （O/Zr） in ZrO2 films deposited for different axial distances （6 cm, 9 cm, and 12 cm） are found to be 2.1, 2.2, and 2.3, respectively. Fourier transform infrared （FTIR） analysis reveals that the bands appearing at 441 cm-1 and 480 cm-1 belong to m-ZrO2 and t-ZrO2 phases, respectively. Maximum microhardness （8.65±0.45 GPa） of ZrO2 film is ～ 6.7 times higher than the microhardness of virgin Zr.展开更多
Soil organic carbon(SOC)is a critical variable used to determine the carbon balance.However,large uncertainties arise when predicting the SOC stock in soil profiles in Chinese grasslands,especially on desert rangeland...Soil organic carbon(SOC)is a critical variable used to determine the carbon balance.However,large uncertainties arise when predicting the SOC stock in soil profiles in Chinese grasslands,especially on desert rangelands.Recent studies have shown that desert ecosystems may be potential carbon sinks under global climate change.Because of the high spatial heterogeneity,time-consuming sampling methods,and difficult acquisition process,the relationships the SOC storage and distribution have with driving factors in desert rangelands remain poorly understood.Here,we investigated and developed an SOC database from 3162 soil samples(collected at depths of 0−10 cm and 10−20 cm)across 527 sites,as well as the climate conditions,vegetation types,and edaphic factors associated with the sampling sites in the desert rangelands of northern Xinjiang,north-west China.This study aims to determine the SOC magnitude and drivers in desert rangelands.Our findings demonstrate that the SOC and SOC density(SOCD)were 0.05−37.13 g·kg^(-1)and 19.23−9740.62 g·m^(-2),respectively,with average values of 6.81±5.31 g·kg^(-1)and 1670.38±1202.52 g·m^(-2),respectively.The spatial distributions of SOC and SOCD all showed gradually decreasing trends from south-west to north-east.High-SOC areas were mainly distributed in the piedmont lowlands of the Ili valley,while low-SOC regions were mainly concentrated in the north-west area of Altay.The redundancy analysis results revealed that all environmental factors accounted for approximately 37.6%of the spatial variability in SOC;climate factors,vegetation factors,and soil properties explained 15.0%,1.7%,and 12.3%,respectively.The structural equation model(SEM)further indicated that evapotranspiration,average annual precipitation,and the SWC were the dominant factors affecting SOC accumulation,mainly through direct effects,although indirect effects were also delivered by the vegetation factors.Taken together,the results obtained herein updated the SOC data pool available for desert rangelands and clarified the main driving factors of SOC variations.This study provided supporting data for the sustainable use and management of desert rangelands and the global ecosystem carbon budget.展开更多
Airborne bacteria play key roles in terrestrial and marine ecosystems and human health,yet our understanding of bacterial communities and their response to the environmental variables lags significantly behind that of...Airborne bacteria play key roles in terrestrial and marine ecosystems and human health,yet our understanding of bacterial communities and their response to the environmental variables lags significantly behind that of other components of PM_(2.5).Here,atmospheric fine particles obtained from urban and suburb Shanghai were analyzed by using the qPCR and Illumina Miseq sequencing.The bacteria with an average concentration of 2.12× 10^(3 )cells/m^(3),were dominated by Sphingomonas,Curvibacter,Acinetobacter,Bradyrhizobium,Methylobacterium,Halomonas,Aliihoeflea,and Phyllobacterium,which were related to the nitrogen,carbon,sulfur cycling and human health risk.Our results provide a global survey of bacterial community across urban,suburb,and high-altitude sites.In Shanghai(China),urban PM2.5 harbour more diverse and dynamic bacterial populations than that in the suburb.The structural equation model explained about 27%,41%,and 20%^78%of the variance found in bacteria diversity,concentration,and discrepant genera among urban and suburb sites.This work furthered the knowledge of diverse bacteria in a coastal Megacity in the Yangtze river delta and emphasized the potential impact of environmental variables on bacterial community structure.展开更多
Laboratory measurements using nuclear magnetic resonance,scanning electron microscopy,and gas porosity and permeability analysis were conducted to acquire a petrophysical interpretation of the Carbon Tan Sandstone and...Laboratory measurements using nuclear magnetic resonance,scanning electron microscopy,and gas porosity and permeability analysis were conducted to acquire a petrophysical interpretation of the Carbon Tan Sandstone and Savonnieres Carbonate for potential carbon dioxide storage in subsurface formations.The relationships between pore structures,such as pore-size distribution,pore geometry,and porosity/permeability,were investigated near and far from the wellbore.At operating pressures of 2500psi(17.24 MPa)and temperatures of 176F(50℃),carbonated water was injected into a composite core constructed of two similar core samples bounded by a compact disc located between them.The current results showed that a strong calcite dissolution took place near the injection position of both rock samples and led to improvements in the primary intergranular permeability and porosity,while the carbonate sample showed significant improvement compared to sandstone.The durable heterogeneous dissolution of calcite grains also led to the creation of new pores as intra-granular micro-pores.While at deeper depths from the injection position,it noticed an insignificant development in pore structure and its populations as well as rock hydraulic properties of both rock samples.In conclusion,the study revealed that the injected carbonated brine had a valuable impact on fluid-formation interactive,which improved rock's inlet properties compared with outlet.展开更多
文摘Three types of rock specimens, three-point bending specimen, anti-symmetric four-point bending specimen and direct shearing specimen, were used to achieve Mode I, Mode II and mixed mode I–II fracture, respectively. Microscopic characteristics of the three fracture modes of brittle rock were studied by SEM technique in order to analyze fracture behaviors and better understand fracture mechanisms of different fracture modes of brittle rock. Test results show that the microscopic characteristics of different fracture modes correspond to different fracture mechanisms. The surface of Mode I fracture has a great number of sparse and steep slip-steps with few tearing ridges and shows strong brittleness. In the surface of Mode II fracture there exist many tearing ridges and densely distributed parallel slip-steps and it is attributed to the action of shear stress. The co-action of tensile and shear stresses results in brittle cleavage planes mixed with streamline patterns and tearing ridges in the surface of mixed mode I–II fracture. The measured Mode II fracture toughness K II C and mixed mode I–II fracture toughness K mC are larger than Mode I fracture toughness K I C · K II C is about 3.5 times K I C, and KmC is about 1.2 times K I C.
文摘2-Acrylamido-2-methyl-1-propanesulfonic acid （AMPS）, and maleic acid （MA） copolymerized with different feed ratios using N,N-dimethylformamide as a solvent and benzoyl peroxide （Bz2O2） as an initiator at 70℃. Structure and composition of copolymers for a wide range of monomer feed were determined by elemental analysis （content of N for AMPS-units）. Monomer reactivity ratios for AMPS （M1）-MA （M2） pair were determined by the application of conventional linearization methods such as Fineman-Ross （F-R）, Kelen-Tudos（KT） and Extended Kelen-Tudos （EKT） and a nonlinear error invariable model method using a computer program RREVM. The characterizations were done by Fourier transform infrared spectroscopy （FTIR）, differential scanning calorimetry （DSC） thermal gravimetry analysis （TGA）, and and X-ray diffraction. The antimicrobial effects of polymers were also tested on various bacteria, and yeast.
基金funded by the National Natural Science Foundation of China (Grant No.11972018)sponsored by the Defense Pre-Research Joint Foundation of Chinese Ordnance Industry (Grant No. 6141B012858)。
文摘In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.
基金Project supported by the Higher Education Commission of Pakistan
文摘Nanostructured multiphase zirconia films （MZFs） are deposited on Zr substrate by the irradiation of energetic oxygen ions emanated from a plasma focus device. The oxygen operating gas pressure of 1 mbar （1 bar=105 Pa） provides the most appropriate ion energy flux to deposit crystalline ZrO2 films. X-ray diffraction （XRD） patterns reveal the formation of polycrystalline ZrO2 films. The crystallite size （CS）, crystal growth, and dislocation densities are attributed to increasing focus shots, sample axial distances, and working gas pressures. Phase and orientation transformations from t-ZrO2 to m-ZrO2 and c-ZrO2 are associated with increasing focus shots and continuous annealing. For lower （200 ℃） annealing temperature （AT）, full width at half maximum （FWHM） of diffraction peak, CS, and dislocation density （δ） for （020） plane are found to be 0.494, 16.6 nm, and 3.63×10-3 nm-2 while for higher （400 ℃） AT, these parameters for （111） plane are found to be 0.388, 20.87 nm, and 2.29×10-3 nm-2, respectively. Scanning electron microscope （SEM） results demonstrate the formation of rounded grains with uniform distribution. The estimated values of atomic ratio （O/Zr） in ZrO2 films deposited for different axial distances （6 cm, 9 cm, and 12 cm） are found to be 2.1, 2.2, and 2.3, respectively. Fourier transform infrared （FTIR） analysis reveals that the bands appearing at 441 cm-1 and 480 cm-1 belong to m-ZrO2 and t-ZrO2 phases, respectively. Maximum microhardness （8.65±0.45 GPa） of ZrO2 film is ～ 6.7 times higher than the microhardness of virgin Zr.
基金funded by the Open Project of Key Laboratory of Xinjiang Uygur Autonomous Region(No.2022D04003)the National Basic resource survey of China(No.2017FY100200)+1 种基金the National Natural Science Foundation of China(Grant No.32060408)the graduate scientific research and innovation project of Xinjiang Agricultural University(No.XJAUGRI2021003).
文摘Soil organic carbon(SOC)is a critical variable used to determine the carbon balance.However,large uncertainties arise when predicting the SOC stock in soil profiles in Chinese grasslands,especially on desert rangelands.Recent studies have shown that desert ecosystems may be potential carbon sinks under global climate change.Because of the high spatial heterogeneity,time-consuming sampling methods,and difficult acquisition process,the relationships the SOC storage and distribution have with driving factors in desert rangelands remain poorly understood.Here,we investigated and developed an SOC database from 3162 soil samples(collected at depths of 0−10 cm and 10−20 cm)across 527 sites,as well as the climate conditions,vegetation types,and edaphic factors associated with the sampling sites in the desert rangelands of northern Xinjiang,north-west China.This study aims to determine the SOC magnitude and drivers in desert rangelands.Our findings demonstrate that the SOC and SOC density(SOCD)were 0.05−37.13 g·kg^(-1)and 19.23−9740.62 g·m^(-2),respectively,with average values of 6.81±5.31 g·kg^(-1)and 1670.38±1202.52 g·m^(-2),respectively.The spatial distributions of SOC and SOCD all showed gradually decreasing trends from south-west to north-east.High-SOC areas were mainly distributed in the piedmont lowlands of the Ili valley,while low-SOC regions were mainly concentrated in the north-west area of Altay.The redundancy analysis results revealed that all environmental factors accounted for approximately 37.6%of the spatial variability in SOC;climate factors,vegetation factors,and soil properties explained 15.0%,1.7%,and 12.3%,respectively.The structural equation model(SEM)further indicated that evapotranspiration,average annual precipitation,and the SWC were the dominant factors affecting SOC accumulation,mainly through direct effects,although indirect effects were also delivered by the vegetation factors.Taken together,the results obtained herein updated the SOC data pool available for desert rangelands and clarified the main driving factors of SOC variations.This study provided supporting data for the sustainable use and management of desert rangelands and the global ecosystem carbon budget.
基金by the Shanghai Sailing Program(19YF1403200)National Natural Science Foundation of China(Grant Nos.21906023,91843301,91743202,21527814)+2 种基金Ministry of Science and Technology of China(No.2016YFC0202700)Marie Skto-dowska-Curie Actions(690958-MARSU-RISE-2015)China Postdoctoral Science Foundation(No.2018M640331).
文摘Airborne bacteria play key roles in terrestrial and marine ecosystems and human health,yet our understanding of bacterial communities and their response to the environmental variables lags significantly behind that of other components of PM_(2.5).Here,atmospheric fine particles obtained from urban and suburb Shanghai were analyzed by using the qPCR and Illumina Miseq sequencing.The bacteria with an average concentration of 2.12× 10^(3 )cells/m^(3),were dominated by Sphingomonas,Curvibacter,Acinetobacter,Bradyrhizobium,Methylobacterium,Halomonas,Aliihoeflea,and Phyllobacterium,which were related to the nitrogen,carbon,sulfur cycling and human health risk.Our results provide a global survey of bacterial community across urban,suburb,and high-altitude sites.In Shanghai(China),urban PM2.5 harbour more diverse and dynamic bacterial populations than that in the suburb.The structural equation model explained about 27%,41%,and 20%^78%of the variance found in bacteria diversity,concentration,and discrepant genera among urban and suburb sites.This work furthered the knowledge of diverse bacteria in a coastal Megacity in the Yangtze river delta and emphasized the potential impact of environmental variables on bacterial community structure.
基金funded by Curtin Malaysia Collaborative Research(CMCR)grant(004022).
文摘Laboratory measurements using nuclear magnetic resonance,scanning electron microscopy,and gas porosity and permeability analysis were conducted to acquire a petrophysical interpretation of the Carbon Tan Sandstone and Savonnieres Carbonate for potential carbon dioxide storage in subsurface formations.The relationships between pore structures,such as pore-size distribution,pore geometry,and porosity/permeability,were investigated near and far from the wellbore.At operating pressures of 2500psi(17.24 MPa)and temperatures of 176F(50℃),carbonated water was injected into a composite core constructed of two similar core samples bounded by a compact disc located between them.The current results showed that a strong calcite dissolution took place near the injection position of both rock samples and led to improvements in the primary intergranular permeability and porosity,while the carbonate sample showed significant improvement compared to sandstone.The durable heterogeneous dissolution of calcite grains also led to the creation of new pores as intra-granular micro-pores.While at deeper depths from the injection position,it noticed an insignificant development in pore structure and its populations as well as rock hydraulic properties of both rock samples.In conclusion,the study revealed that the injected carbonated brine had a valuable impact on fluid-formation interactive,which improved rock's inlet properties compared with outlet.
