The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In th...The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In this work,magnetic poly(butyleneadipate-coterephthalate)(PBAT)microspheres were firstly synthesized via phase separation method,then PBAT composite foams with layered structure was constructed through the supercritical carbon dioxide foaming and scraping techniques.The merits of integrating ferroferric oxideloaded multi-walled carbon nanotubes(Fe3O4@MWCNTs)nanoparticles,a microcellular framework,and a highly conductive silver layer have been judiciously orchestrated within this distinctive layered configuration.Microwaves are consumed throughout the process of“absorption-reflection-reabsorption”as much as possible,which greatly declines the secondary radiation pollution.The biodegradable PBAT composite foams achieved an EMI shielding effectiveness of up to 68 dB and an absorptivity of 77%,and authenticated favorable stabilization after the tape adhesion experiment.展开更多
A new technique, powder compact foaming process for the production of aluminumfoams has been studied in this article. According to this method, the aluminum pow-der is mixed with a powder foaming agent (TiH_2). Subseq...A new technique, powder compact foaming process for the production of aluminumfoams has been studied in this article. According to this method, the aluminum pow-der is mixed with a powder foaming agent (TiH_2). Subsequent to mixing, the powderblend is hot compacted to obtain a dense semi--finished product. Upon heating to tem-peratures within the range of the melting point, the foaming agent decomposes to evolvegas and the semi--finished product expands into a porous cellular aluminum. Foamingprocess is the key in this method. Based on experiments, the foaming characteris-tics were mainly analyzed and discussed. Experiments show that the aluminum--foamwith closed pores and a uniform cell structure of high porosity can be obtained usingthis method by adjusting the foaming parameters: the content of foaming agent andfoaming temperature.展开更多
A profile of shallow crustal velocity structure(1–2 km) may greatly enhance interpretation of the sedimentary environment and shallow tectonic deformation.Recent advances in surface wave tomography, using ambient noi...A profile of shallow crustal velocity structure(1–2 km) may greatly enhance interpretation of the sedimentary environment and shallow tectonic deformation.Recent advances in surface wave tomography, using ambient noise data recorded with high-density seismic arrays, have improved the understanding of regional crustal structure. As the interest in detailed shallow crustal structure imaging has increased, dense seismic array methods have become increasingly efficient. This study used a high-density seismic array deployed in the Xinjiang basin in southeastern China, to record seismic data, which was then processed with the ambient noise tomography method. The high-density seismic array contained 203 short-period seismometers, spaced at short intervals(~ 400 m). The array collected continuous records of ambient noise for 32 days. Data preprocessing,cross correlation calculation, and Rayleigh surface wave phase-velocity dispersion curve extraction, yielded more than 16,000 Rayleigh surface wave phase-velocity dispersion curves, which were then analyzed using the direct-inversion method. Checkerboard tests indicate that the shear wave velocity is recovered in the study area, at depths of 0–1.4 km,with a lateral image resolution of ~ 400 m. Model test results show that the seismic array effectively images a 50 m thick slab at a depth of 0–300 m, a 150 m thick anomalous body at a depth of 300–600 m, and a 400 m thick anomalous body at a depth of 0.6–1.4 km. The shear wave velocity profile reveals features very similar to those detected by a deep seismic reflection profile across the study area. This demonstrates that analysis of shallow crustal velocity structure provides high-resolution imaging of crustal features.Thus, ambient noise tomography with a high-density seismic array may play an important role in imaging shallow crustal structure.展开更多
In order to solve the issue that the combustible objects for cased telescoped ammunition (CTA) didn't burn completely during the combustion process, the microcellular combustible objects were foamed with numerous ...In order to solve the issue that the combustible objects for cased telescoped ammunition (CTA) didn't burn completely during the combustion process, the microcellular combustible objects were foamed with numerous cells in the micron order to improve the combustion performance by the supercritical carbon dioxide (SCeCO2) foaming technology. As the cell structure determined the combustion properties of microcellular combustible objects, the solubility of SCeCO2 dissolved into the combustible objects was obtained from the gravimetric method, and scanning electron microscope (SEM) was applied to characterize the cell structure under various process conditions of solubility, foaming temperature and foaming time. SEM images indicate that the cell diameter of microcellular combustible objects is in the level of 1 mm and the cell density is about 1011 cell,cm^-3. The microcellular combustible objects fabricated by the SCeCO2 foaming technology are smooth and uniform, and the high specific surface area of cell structure can lead to the significant combustion performance of microcellular combustible object for CTA in the future.展开更多
Based on the mechanical properties and microstructure of polyurethane foam solidified material, a two-dimensional model of polyurethane foam solidified material was constructed. Polyurethane foam was obtained by fully...Based on the mechanical properties and microstructure of polyurethane foam solidified material, a two-dimensional model of polyurethane foam solidified material was constructed. Polyurethane foam was obtained by fully and uniformly mixing the two components. The research was carried out through the combination of experimental test and finite element simulation. The experimental results show that when the pore density is constant, the size of the bubble hole is an important factor affecting the mechanical properties of the model. The smaller the size of the bubble hole, the less likely it is to produce stress concentration inside the model, and the stronger the resistance to material deformation. Under the random distribution, the lower the density of the polyurethane cured material, the higher the probability of damage between the adjacent bubbles, which is not conducive to the stability of the material. The density of the cured material should not be lower than 199 kg/m^3.展开更多
Silicalite-1(S1)foam was functionalized by supporting manganese-cobalt(Mn-Co)mixed oxides to develop the structured hierarchical catalyst(Mn-Co@SlF)for catalytic combustion for the first time.The self-supporting S1 fo...Silicalite-1(S1)foam was functionalized by supporting manganese-cobalt(Mn-Co)mixed oxides to develop the structured hierarchical catalyst(Mn-Co@SlF)for catalytic combustion for the first time.The self-supporting S1 foam with hierarchical porosity was prepared via hydrothermal synthesis with polyurethane(PU)foam as the template.Subsequently,Mn-Co oxide nano sheets were uniformly grown on the surface of S1 foams under hydrothermal conditions to prepare the structured hierarchical catalyst with specific surface area of 354 m^2·g^-1,micropore volume of 0.141 cm^3·g^-1 and total pore volume of 0.217 cm3·g^-1,as well as a good capacity to adsorb toluene(1.7 mmol·g^-1 at p/p0=0.99).Comparative catalytic combustion of toluene of over developed structured catalyst Mn-Co@SlF was performed against the control catalysts of bulk Mn-Co@S1(i.e.,the crushed Mn-Co@SlF)and unsupported Mn-Co oxides(i.e.,Mn-Co).Mn-Co@SlF exhibited comparatively the best catalytic performance,that is,complete and stable toluene conversion at 2480 C over 65 h due to the synergy between Mn-Co oxides and S1 foam,which provided a large number of oxygen vacancies,high redox capacity.In addition,the hierarchical porous structure also improved the accessibility of active sites and facilitated the global mass transfer across the catalyst bed,being beneficial to the catalysis and catalyst longevity.展开更多
The reflection characteristics of gird structures are calculated by the spatial network method in the case of normal incidence plane electromagnetic wave. The numerical result shows that the grid panels without electr...The reflection characteristics of gird structures are calculated by the spatial network method in the case of normal incidence plane electromagnetic wave. The numerical result shows that the grid panels without electromagnetic wave absorbing foams are not ideal. However, the absorbing ability can be achieved as low as -25 dBsm from 8 GHz to 12 GHz when the grid cells are filled with foam absorbers. Also it is noted from computation that the foam filled grid structures with larger cell size, higher and thinner ribs will improve the absorbing abilities, which illustrates that they can be used as the effective light-weight stealth structures for aeronautical application.展开更多
A rotating packed bed(RPB) reactor has substantially potential for the process intensification of heterogeneous catalytic reactions. However, the scarce knowledge of the liquid–solid mass transfer in the RPB reactor ...A rotating packed bed(RPB) reactor has substantially potential for the process intensification of heterogeneous catalytic reactions. However, the scarce knowledge of the liquid–solid mass transfer in the RPB reactor is a barrier for its design and scale-up. In this work, the liquid–solid mass transfer in a RPB reactor installed with structured foam packing was experimentally studied using copper dissolution by potassium dichromate. Effects of rotational speed, liquid and gas volumetric flow rate on the liquid–solid mass transfer coefficient(kLS) have been investigated. The correlation for predicting kLSwas proposed, and the deviation between the experimental and predicted values was within±12%. The liquid–solid volumetric mass transfer coefficient(kLSaLS) ranged from 0.04–0.14 1^-1, which was approximately 5 times larger than that in the packed bed reactor. This work lays the foundation for modeling of the RPB reactor packed with structured foam packing for heterogeneous catalytic reaction.展开更多
Phase-field modeling for three-dimensional foam structures is presented. The foam structure, which is generally applicable for porous material design, is geometrically approximated with a space-filling structure, and ...Phase-field modeling for three-dimensional foam structures is presented. The foam structure, which is generally applicable for porous material design, is geometrically approximated with a space-filling structure, and hence, the analysis of the space-filling structure was performed using the phase field model. An additional term was introduced to the conventional multi-phase field model to satisfy the volume constraint condition. Then, the equations were numerically solved using the finite difference method, and simulations were carried out for several nuclei settings. First, the nuclei were set on complete lattice points for a bcc or fcc arrangement, with a truncated hexagonal structure, which is known as a Kelvin cell, or a rhombic dodecahedron being obtained, respectively. Then, an irregularity was introduced in the initial nuclei arrangement. The results revealed that the truncated hexagonal structure was stable against a slight irregularity, whereas the rhombic polyhedral was destroyed by the instability. Finally, the nuclei were placed randomly, and the relaxation process of a certain cell was traced with the result that every cell leads to a convex polyhedron shape.展开更多
By determining the distribution and extent of geological structures surrounding the Mingyan Tunnel,Xicheng Town,Helong City,Jilin Province,we can evaluate the stability of the rock mass and assess potential hazards du...By determining the distribution and extent of geological structures surrounding the Mingyan Tunnel,Xicheng Town,Helong City,Jilin Province,we can evaluate the stability of the rock mass and assess potential hazards during tunnel construction.We use the high-density resistivity method to analyze the subsurface structure of the study area.Conductive anomalies are likely to represent joint and fissure systems within strongly weathered host rocks,and the bedrock surrounding the tunnel is relatively stable and does not contain well-developed faults.High-density resistivity analysis can provide valuable information in the context of tunnel engineering and safety.展开更多
The authors employ the high-density resistivity method to image the subsurface structure of a mountain in Erdaojiang District,Tonghua City,Jilin Province,China,to evaluate the potential risk of slope failure on surrou...The authors employ the high-density resistivity method to image the subsurface structure of a mountain in Erdaojiang District,Tonghua City,Jilin Province,China,to evaluate the potential risk of slope failure on surrounding residential areas and infrastructure,and identify a shallow fault that extends across the center of the mountain and is perpendicular to the mountain slope and accurately locate the spatial position and depth of another fault on the southern side of the mountain.The results provide an important basis for evaluating mountain slope stability.This study also demonstrates that the high-density resistivity method is effective for detecting mountain faults.展开更多
The density, cell size and structure of closed-cell aluminum foam were measured by optical microscopy and image analysis. The properties and the mechanism of compressive deformation that occur in closed-cell aluminum ...The density, cell size and structure of closed-cell aluminum foam were measured by optical microscopy and image analysis. The properties and the mechanism of compressive deformation that occur in closed-cell aluminum foam were measured and discussed. The results show that the cell size of foam with density of 0.37 mg/m^3 is distributed in the range of 0.5 4.0 mm. The cell size of foam with density of 0.33 mg/m^3 is distributed in the range of 0.55.0 mm. The cell wall thickness of both types is 0.10.3 mm. The closed-cell aluminum foam almost belongs to isotropic one, with a variation of ±15% in elastic modulus and yield strength in longitudinal and transverse direction. Under compressive loading, foam materials show inhomogeneous macroscopic deformation. The site of the onset of local plastic deformation depends on the cell structure. The shape of cell is more important than size in determining the yielding susceptibility of the cells. At early stage of deformation,the deformation is localized in narrow bands having width of one cells diameter, and outside the bands the cell still remains the original shape. The cells within bands experience large permanent deformation. The band normals are usually within 20° of the loading axis.展开更多
By use of ICP spectroscopy, energy spectrum analysis, hydrogen tester, image analyzer, the differential scanning calorimetric(DSC) and microscope analysis, the effects of RE on the Porosity, structure and properties o...By use of ICP spectroscopy, energy spectrum analysis, hydrogen tester, image analyzer, the differential scanning calorimetric(DSC) and microscope analysis, the effects of RE on the Porosity, structure and properties of B319 aluminum alloy were studied. The results show that under the 0.3 °C /s slow cooling rate in lost foam casting, the effect of RE on modification and grain size of B319 aluminum alloy is little. With the increase of RE master alloy, the tensile strength and elongation increase. When RE>0.15%, block like La 2Si 2Al 3 phase appear, and the tensile strength and elongation decrease. The results also show that the melt hydrogen content and casting porosity can be decreased greatly by adding 0.15% RE to aluminum melt. This is the important reason why RE improves the mechanical properties of casting under lost foam casting condition.展开更多
High-density electrical method has been proved to be an effective method for probing shallow sedimentary layers.It is principally used to identify the boundary between the Quaternary soil layer and bedrock according t...High-density electrical method has been proved to be an effective method for probing shallow sedimentary layers.It is principally used to identify the boundary between the Quaternary soil layer and bedrock according to the vertical change of apparent resistivity.However,the artificial filling layer has the characteristics of heterogeneity and high porosity,which makes it challenging to detect the artificial filling layer by high-density electrical method.The key to solve this problem is to detect the difference of conductivity between the filling layer and the underlying bedrock.This paper takes the land in Chengjiangshan area of Huaibei City,Anhui Province as the detection target.On the basis of fully analyzing the physical properties of the artificial filling layer,two-dimensional high-density electrical survey and inversion are used to define the thickness of the artificial filling layer.The research shows that the highdensity resistivity method has obvious advantages in delineating the distribution of bedrock and the thickness of the filling layer,and the reliability of the high-density electrical method in the detection of the artificial filling layer,and delineates the scope of the filling layer is verified by the borehole data.展开更多
Some unfavorable geological conditions can affect the construction of tunnels.In order to evaluate the damage degree of tunnel construction and determine the surrounding rock grade and stability of the tunnel,the auth...Some unfavorable geological conditions can affect the construction of tunnels.In order to evaluate the damage degree of tunnel construction and determine the surrounding rock grade and stability of the tunnel,the authors used high-density resistivity method to detect the surrounding rocks of Shimodong tunnel in Xicheng Town of Helong City.The underground resistivity structures of the entrance,exit and middle parts of the tunnel are obtained.Through analysis,it is found that there are no bedrock faults near the tunnel,although some joints and fissures are developed in some locations,which are characterized by low-resistivity anomalies.The tunnel structures are stable overall,favorable for safe and efficient construction.The study also proves the good application effect of the high-density resistivity method in tunnel safety detection.展开更多
The authors employ the high-density resistivity method during an archaeological investigation of Sumicheng site,an ancient city of the Tang Dynasty,to find evidence of human activities and locate a favorable target fo...The authors employ the high-density resistivity method during an archaeological investigation of Sumicheng site,an ancient city of the Tang Dynasty,to find evidence of human activities and locate a favorable target for archaeological excavation in the southern part of the outer city.There are two obvious high-resistivity structures,the south wall of the inner city and an ancient building near the south gate along the outer city wall,of which the resistivities are indicative of rammed soil foundations.The south wall of the inner city is continuous but is cut off abruptly to the east,which we suggest it is due to either wall damage or destruction.The resistivity signature of the target area is verified by archaeological excavation,proving the feasibility and effectiveness of implementing the high-density resistivity method for archaeological exploration.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.U21A2093)the Anhui Provincial Natural Science Foundation(No.2308085QE146)the National Natural Science Foundation of Jiangsu Province(No.BK20210894).
文摘The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In this work,magnetic poly(butyleneadipate-coterephthalate)(PBAT)microspheres were firstly synthesized via phase separation method,then PBAT composite foams with layered structure was constructed through the supercritical carbon dioxide foaming and scraping techniques.The merits of integrating ferroferric oxideloaded multi-walled carbon nanotubes(Fe3O4@MWCNTs)nanoparticles,a microcellular framework,and a highly conductive silver layer have been judiciously orchestrated within this distinctive layered configuration.Microwaves are consumed throughout the process of“absorption-reflection-reabsorption”as much as possible,which greatly declines the secondary radiation pollution.The biodegradable PBAT composite foams achieved an EMI shielding effectiveness of up to 68 dB and an absorptivity of 77%,and authenticated favorable stabilization after the tape adhesion experiment.
文摘A new technique, powder compact foaming process for the production of aluminumfoams has been studied in this article. According to this method, the aluminum pow-der is mixed with a powder foaming agent (TiH_2). Subsequent to mixing, the powderblend is hot compacted to obtain a dense semi--finished product. Upon heating to tem-peratures within the range of the melting point, the foaming agent decomposes to evolvegas and the semi--finished product expands into a porous cellular aluminum. Foamingprocess is the key in this method. Based on experiments, the foaming characteris-tics were mainly analyzed and discussed. Experiments show that the aluminum--foamwith closed pores and a uniform cell structure of high porosity can be obtained usingthis method by adjusting the foaming parameters: the content of foaming agent andfoaming temperature.
基金supported by the China Geological Survey Project“Deep Geological Survey of the Qin-Hang Belt”(No.DD20160082)the National Natural Science Foundation of China(No.41574048)
文摘A profile of shallow crustal velocity structure(1–2 km) may greatly enhance interpretation of the sedimentary environment and shallow tectonic deformation.Recent advances in surface wave tomography, using ambient noise data recorded with high-density seismic arrays, have improved the understanding of regional crustal structure. As the interest in detailed shallow crustal structure imaging has increased, dense seismic array methods have become increasingly efficient. This study used a high-density seismic array deployed in the Xinjiang basin in southeastern China, to record seismic data, which was then processed with the ambient noise tomography method. The high-density seismic array contained 203 short-period seismometers, spaced at short intervals(~ 400 m). The array collected continuous records of ambient noise for 32 days. Data preprocessing,cross correlation calculation, and Rayleigh surface wave phase-velocity dispersion curve extraction, yielded more than 16,000 Rayleigh surface wave phase-velocity dispersion curves, which were then analyzed using the direct-inversion method. Checkerboard tests indicate that the shear wave velocity is recovered in the study area, at depths of 0–1.4 km,with a lateral image resolution of ~ 400 m. Model test results show that the seismic array effectively images a 50 m thick slab at a depth of 0–300 m, a 150 m thick anomalous body at a depth of 300–600 m, and a 400 m thick anomalous body at a depth of 0.6–1.4 km. The shear wave velocity profile reveals features very similar to those detected by a deep seismic reflection profile across the study area. This demonstrates that analysis of shallow crustal velocity structure provides high-resolution imaging of crustal features.Thus, ambient noise tomography with a high-density seismic array may play an important role in imaging shallow crustal structure.
文摘In order to solve the issue that the combustible objects for cased telescoped ammunition (CTA) didn't burn completely during the combustion process, the microcellular combustible objects were foamed with numerous cells in the micron order to improve the combustion performance by the supercritical carbon dioxide (SCeCO2) foaming technology. As the cell structure determined the combustion properties of microcellular combustible objects, the solubility of SCeCO2 dissolved into the combustible objects was obtained from the gravimetric method, and scanning electron microscope (SEM) was applied to characterize the cell structure under various process conditions of solubility, foaming temperature and foaming time. SEM images indicate that the cell diameter of microcellular combustible objects is in the level of 1 mm and the cell density is about 1011 cell,cm^-3. The microcellular combustible objects fabricated by the SCeCO2 foaming technology are smooth and uniform, and the high specific surface area of cell structure can lead to the significant combustion performance of microcellular combustible object for CTA in the future.
基金Funded by the National Innovation Platform Open Fund(No.2017YJ163)
文摘Based on the mechanical properties and microstructure of polyurethane foam solidified material, a two-dimensional model of polyurethane foam solidified material was constructed. Polyurethane foam was obtained by fully and uniformly mixing the two components. The research was carried out through the combination of experimental test and finite element simulation. The experimental results show that when the pore density is constant, the size of the bubble hole is an important factor affecting the mechanical properties of the model. The smaller the size of the bubble hole, the less likely it is to produce stress concentration inside the model, and the stronger the resistance to material deformation. Under the random distribution, the lower the density of the polyurethane cured material, the higher the probability of damage between the adjacent bubbles, which is not conducive to the stability of the material. The density of the cured material should not be lower than 199 kg/m^3.
基金financial support from the Key Projects of Natural Science Foundation of Liaoning Province(2018010047-301)the Shenyang National Laboratory for Materials Science for his research(Y8L6641161)+1 种基金financial support from the National Key R&D Program of China(2016YFB0501303)funding from European Union's Horizon 2020 research and innovation programme under grant agreement No.872102。
文摘Silicalite-1(S1)foam was functionalized by supporting manganese-cobalt(Mn-Co)mixed oxides to develop the structured hierarchical catalyst(Mn-Co@SlF)for catalytic combustion for the first time.The self-supporting S1 foam with hierarchical porosity was prepared via hydrothermal synthesis with polyurethane(PU)foam as the template.Subsequently,Mn-Co oxide nano sheets were uniformly grown on the surface of S1 foams under hydrothermal conditions to prepare the structured hierarchical catalyst with specific surface area of 354 m^2·g^-1,micropore volume of 0.141 cm^3·g^-1 and total pore volume of 0.217 cm3·g^-1,as well as a good capacity to adsorb toluene(1.7 mmol·g^-1 at p/p0=0.99).Comparative catalytic combustion of toluene of over developed structured catalyst Mn-Co@SlF was performed against the control catalysts of bulk Mn-Co@S1(i.e.,the crushed Mn-Co@SlF)and unsupported Mn-Co oxides(i.e.,Mn-Co).Mn-Co@SlF exhibited comparatively the best catalytic performance,that is,complete and stable toluene conversion at 2480 C over 65 h due to the synergy between Mn-Co oxides and S1 foam,which provided a large number of oxygen vacancies,high redox capacity.In addition,the hierarchical porous structure also improved the accessibility of active sites and facilitated the global mass transfer across the catalyst bed,being beneficial to the catalysis and catalyst longevity.
基金Funded by the National Natural Science Foundation of China(No.10572012)
文摘The reflection characteristics of gird structures are calculated by the spatial network method in the case of normal incidence plane electromagnetic wave. The numerical result shows that the grid panels without electromagnetic wave absorbing foams are not ideal. However, the absorbing ability can be achieved as low as -25 dBsm from 8 GHz to 12 GHz when the grid cells are filled with foam absorbers. Also it is noted from computation that the foam filled grid structures with larger cell size, higher and thinner ribs will improve the absorbing abilities, which illustrates that they can be used as the effective light-weight stealth structures for aeronautical application.
基金supported by the National Natural Science Foundation of China(Nos.21676009 and 21725601)。
文摘A rotating packed bed(RPB) reactor has substantially potential for the process intensification of heterogeneous catalytic reactions. However, the scarce knowledge of the liquid–solid mass transfer in the RPB reactor is a barrier for its design and scale-up. In this work, the liquid–solid mass transfer in a RPB reactor installed with structured foam packing was experimentally studied using copper dissolution by potassium dichromate. Effects of rotational speed, liquid and gas volumetric flow rate on the liquid–solid mass transfer coefficient(kLS) have been investigated. The correlation for predicting kLSwas proposed, and the deviation between the experimental and predicted values was within±12%. The liquid–solid volumetric mass transfer coefficient(kLSaLS) ranged from 0.04–0.14 1^-1, which was approximately 5 times larger than that in the packed bed reactor. This work lays the foundation for modeling of the RPB reactor packed with structured foam packing for heterogeneous catalytic reaction.
文摘Phase-field modeling for three-dimensional foam structures is presented. The foam structure, which is generally applicable for porous material design, is geometrically approximated with a space-filling structure, and hence, the analysis of the space-filling structure was performed using the phase field model. An additional term was introduced to the conventional multi-phase field model to satisfy the volume constraint condition. Then, the equations were numerically solved using the finite difference method, and simulations were carried out for several nuclei settings. First, the nuclei were set on complete lattice points for a bcc or fcc arrangement, with a truncated hexagonal structure, which is known as a Kelvin cell, or a rhombic dodecahedron being obtained, respectively. Then, an irregularity was introduced in the initial nuclei arrangement. The results revealed that the truncated hexagonal structure was stable against a slight irregularity, whereas the rhombic polyhedral was destroyed by the instability. Finally, the nuclei were placed randomly, and the relaxation process of a certain cell was traced with the result that every cell leads to a convex polyhedron shape.
基金Supported by The National Natural Science Foundation of China(41504076)Jilin Science and Technological Development Program(20180101093JC)。
文摘By determining the distribution and extent of geological structures surrounding the Mingyan Tunnel,Xicheng Town,Helong City,Jilin Province,we can evaluate the stability of the rock mass and assess potential hazards during tunnel construction.We use the high-density resistivity method to analyze the subsurface structure of the study area.Conductive anomalies are likely to represent joint and fissure systems within strongly weathered host rocks,and the bedrock surrounding the tunnel is relatively stable and does not contain well-developed faults.High-density resistivity analysis can provide valuable information in the context of tunnel engineering and safety.
基金Supported by National Key R&D Program of China and Fundamental Research Funds for the Central Universities(2017YFC0601305)。
文摘The authors employ the high-density resistivity method to image the subsurface structure of a mountain in Erdaojiang District,Tonghua City,Jilin Province,China,to evaluate the potential risk of slope failure on surrounding residential areas and infrastructure,and identify a shallow fault that extends across the center of the mountain and is perpendicular to the mountain slope and accurately locate the spatial position and depth of another fault on the southern side of the mountain.The results provide an important basis for evaluating mountain slope stability.This study also demonstrates that the high-density resistivity method is effective for detecting mountain faults.
文摘The density, cell size and structure of closed-cell aluminum foam were measured by optical microscopy and image analysis. The properties and the mechanism of compressive deformation that occur in closed-cell aluminum foam were measured and discussed. The results show that the cell size of foam with density of 0.37 mg/m^3 is distributed in the range of 0.5 4.0 mm. The cell size of foam with density of 0.33 mg/m^3 is distributed in the range of 0.55.0 mm. The cell wall thickness of both types is 0.10.3 mm. The closed-cell aluminum foam almost belongs to isotropic one, with a variation of ±15% in elastic modulus and yield strength in longitudinal and transverse direction. Under compressive loading, foam materials show inhomogeneous macroscopic deformation. The site of the onset of local plastic deformation depends on the cell structure. The shape of cell is more important than size in determining the yielding susceptibility of the cells. At early stage of deformation,the deformation is localized in narrow bands having width of one cells diameter, and outside the bands the cell still remains the original shape. The cells within bands experience large permanent deformation. The band normals are usually within 20° of the loading axis.
文摘By use of ICP spectroscopy, energy spectrum analysis, hydrogen tester, image analyzer, the differential scanning calorimetric(DSC) and microscope analysis, the effects of RE on the Porosity, structure and properties of B319 aluminum alloy were studied. The results show that under the 0.3 °C /s slow cooling rate in lost foam casting, the effect of RE on modification and grain size of B319 aluminum alloy is little. With the increase of RE master alloy, the tensile strength and elongation increase. When RE>0.15%, block like La 2Si 2Al 3 phase appear, and the tensile strength and elongation decrease. The results also show that the melt hydrogen content and casting porosity can be decreased greatly by adding 0.15% RE to aluminum melt. This is the important reason why RE improves the mechanical properties of casting under lost foam casting condition.
文摘High-density electrical method has been proved to be an effective method for probing shallow sedimentary layers.It is principally used to identify the boundary between the Quaternary soil layer and bedrock according to the vertical change of apparent resistivity.However,the artificial filling layer has the characteristics of heterogeneity and high porosity,which makes it challenging to detect the artificial filling layer by high-density electrical method.The key to solve this problem is to detect the difference of conductivity between the filling layer and the underlying bedrock.This paper takes the land in Chengjiangshan area of Huaibei City,Anhui Province as the detection target.On the basis of fully analyzing the physical properties of the artificial filling layer,two-dimensional high-density electrical survey and inversion are used to define the thickness of the artificial filling layer.The research shows that the highdensity resistivity method has obvious advantages in delineating the distribution of bedrock and the thickness of the filling layer,and the reliability of the high-density electrical method in the detection of the artificial filling layer,and delineates the scope of the filling layer is verified by the borehole data.
基金National Key R&D Program of China(2017YFC0601305)Fundamental Research Funds for the Central Universities.
文摘Some unfavorable geological conditions can affect the construction of tunnels.In order to evaluate the damage degree of tunnel construction and determine the surrounding rock grade and stability of the tunnel,the authors used high-density resistivity method to detect the surrounding rocks of Shimodong tunnel in Xicheng Town of Helong City.The underground resistivity structures of the entrance,exit and middle parts of the tunnel are obtained.Through analysis,it is found that there are no bedrock faults near the tunnel,although some joints and fissures are developed in some locations,which are characterized by low-resistivity anomalies.The tunnel structures are stable overall,favorable for safe and efficient construction.The study also proves the good application effect of the high-density resistivity method in tunnel safety detection.
基金projects of Jilin Provincial Institute of Cultural Relics and Archaeology(No.3S318B564423)National Key R&D Program of China(No.2017YFC0601305)Fundamental Research Funds for the Central Universities.
文摘The authors employ the high-density resistivity method during an archaeological investigation of Sumicheng site,an ancient city of the Tang Dynasty,to find evidence of human activities and locate a favorable target for archaeological excavation in the southern part of the outer city.There are two obvious high-resistivity structures,the south wall of the inner city and an ancient building near the south gate along the outer city wall,of which the resistivities are indicative of rammed soil foundations.The south wall of the inner city is continuous but is cut off abruptly to the east,which we suggest it is due to either wall damage or destruction.The resistivity signature of the target area is verified by archaeological excavation,proving the feasibility and effectiveness of implementing the high-density resistivity method for archaeological exploration.