The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analy...The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analysis scheme is proposed in this paper to investigate the soil deformation behavior under the coupling of stress and drying-wetting cycles.A new device is developed based on CT(computerized tomography)workstation to apply certain normal and shear stresses on a soil specimen during drying-wetting cycles.A series of tests are conducted on a type of loess with various coupling of stress paths and drying-wetting cycles.At macroscopic level,stress sensor and laser sensor are used to acquire stress and strain,respectively.The shear and volumetric strain increase during the first few drying-wetting cycles and then become stable.The increase of the shear stress level or confining pressure would cause higher increase rate and the value of shear strain in the process of drying-wetting cycles.At microscopic level,the grayscale value(GSV)of CT scanning image is characterized as the proportion of soil particles to voids.A fabric state parameter is proposed to characterize soil microstructures under the influence of stress and drying-wetting cycle.Test results indicate that the macroand micro-responses show high consistence and relevance.The stress and drying-wetting cycles would both induce collapse of the soil microstructure,which dominants degradation of the soil mechanical properties.The evolution of the macro-mechanical property of soil exhibits a positive linear relationship with the micro-evolution of the fabric state parameter.展开更多
The relation of mass, stiffness and rate of damping is obtained by using the mechanical analysis of the obstructive vibration system of two dimensions for the design of the obstructive vibration system of more freedom...The relation of mass, stiffness and rate of damping is obtained by using the mechanical analysis of the obstructive vibration system of two dimensions for the design of the obstructive vibration system of more freedom and the micro vibration test bed. The result of stimulational experiment indicates that the isolation of vibration of this system is satisfactory. The design method of vibration can be used as the reference to ultra precision machine tool, super micro orientation machanism and so on.展开更多
Objective To test Calcium ion(Ca2+) flow at the head and end of outer hair cells(OHCs) in resting state and in response to Nimodipine treatment.Methods Non-invasive micro-test techniques were used to study Ca2+ in iso...Objective To test Calcium ion(Ca2+) flow at the head and end of outer hair cells(OHCs) in resting state and in response to Nimodipine treatment.Methods Non-invasive micro-test techniques were used to study Ca2+ in isolated OHCs in adult guinea pigs.Results Four types of Ca2+ transport were identified in OHCs on basilar membrane tissue fragments:influx at the head of with efflux at the bottom(type 1):efflux at the head of OHCs with influx at the bottom(type 2);influx at the both head and bottom(type 3);and efflux at the both head and bottom(type 4).However,only type 1 and type 3 of Ca2+ ion transport were detected in the cochlea.We propose that Ca2+ ion transport exists in adult guinea pig cochlear OHCs in resting state and is variable.Ca2 + flow in OHC can be inhibited by Nimodipine in resting state.展开更多
A micro shear testing method which can suit to measure the mechanical properties of heterogeneous materials is introduced, and the properties in each zone of welded joint for CO2 arc welding can be evaluated by using ...A micro shear testing method which can suit to measure the mechanical properties of heterogeneous materials is introduced, and the properties in each zone of welded joint for CO2 arc welding can be evaluated by using this method in this paper. Moreover, these results are compared with those results of Charpy V-notch impact test and their correlation is discussed.展开更多
Toarcian claystone such as that of the Callovo-Oxfordian is a qualified multiphase material. The claystone samples tested in this study are composed of four main mineral phases: silicates(clay minerals, quartz,feldspa...Toarcian claystone such as that of the Callovo-Oxfordian is a qualified multiphase material. The claystone samples tested in this study are composed of four main mineral phases: silicates(clay minerals, quartz,feldspars, micas)(z86%), sulphides(pyrite)(z3%), carbonates(calcite, dolomite)(z10%) and organic kerogen(z1%). Three sets of measurements of the modulus of deformability were compared as determined in(i) nanoindentation tests with a constant indentation depth of 2 mm,(ii) micro-indentation tests with a constant indentation depth of 20 mm, and(iii) meso-compression tests with a constant displacement of 200 mm. These three experimental methods have already been validated in earlier studies. The main objective of this study is to demonstrate the influence of the scaling effect on the modulus of deformability of the material. Different frequency distributions of the modulus of deformability were obtained at the different sample scales:(i) in nano-indentation tests, the distribution was spread between 15 GPa and 90 GPa and contained one peak at34 GPa and another at 51 GPa;(ii) in the micro-indentation tests, the distribution was spread between 25 GPa and 60 GPa and displayed peaks at 26 GPa and 37 GPa; and(iii) in the meso-compression tests, a narrow frequency distribution was obtained, ranging from 25 GPa to 50 GPa and with a maximum at around 35 GPa.展开更多
Based on three kinds of dynamic test of MEMS, a dynamic system for the vibration test of micro machined gyroscope based on high speed photography is introduced. Firstly, the architecture of the system hardware is intr...Based on three kinds of dynamic test of MEMS, a dynamic system for the vibration test of micro machined gyroscope based on high speed photography is introduced. Firstly, the architecture of the system hardware is introduced. Secondly, the image tracking performance is compared by the test using the template matching algorithm, the mean shift algorithm and the SURF algorithm. The vibration curve shows that high speed photograph combined with SURF algorithm is faster, more ac- curate, and more suitable for the vibration test of micro machined gyroscope. After the frequency a- nalysis and related interpolation, more characteristics of micro gyroscope can be obtained.展开更多
To measure projectile attitude in space flight, based on continuous wave （CW） radar, a new micro-Doppler effect testing technique is developed in this paper. It also establishes radar testing model for attitude of f...To measure projectile attitude in space flight, based on continuous wave （CW） radar, a new micro-Doppler effect testing technique is developed in this paper. It also establishes radar testing model for attitude of flying projectile and resolve micro-Doppler effect of projectile motion attitude. By distinguishing and geting attitude parameters such as micro-motion period, this technique can in- tuitively estimate the flight stability of projectile, and the validity of this technique is proved accord- ing to flight tests.展开更多
Ceramic coatings were prepared on Ti-6Al-4V alloy in NaAlO2 solution by micro-plasma oxidation （MPO）. The salt spray tests of the coated samples and the substrates were carded out in a salt spray test machine. The p...Ceramic coatings were prepared on Ti-6Al-4V alloy in NaAlO2 solution by micro-plasma oxidation （MPO）. The salt spray tests of the coated samples and the substrates were carded out in a salt spray test machine. The phase composition and surface morphology of the coatings were investigated by XRD and SEAM. Severe corrosion occurred on the substrate surface, while there were no obvious corrosion phenomena on the coated samples. The coatings were composed of Al2TiO5 and a little α-Al2O3 and mille TiO2, and the salt spray test did not change the composition of the coatings. The weight loss rate of the coatings decreased with increasing MPO time because of the increase in density and thickness of the coatings. The surface morphology of the coatings was influenced by salt spray corrosion test. Among the coated samples, the coating prepared for 2 h has the best corrosion resistance under salt spray test.展开更多
Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenie...Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenient for micro power generation (5 - 30 kW) is because of their heaviness. Micro and ultra micro gas turbine devices, based on a micro compressor and a micro turbine installed on the same shaft, are more suitable for this scope for several reasons. Micro turbine systems have many advantages over reciprocating engine generators, such as higher power density (with respect to size and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. Micro turbines also have the advantage of having the majority of their waste heat contained in their relatively high temperature exhaust. Micro turbines offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels. The object of this study is the experimental tests on a stand-alone gas turbine device with a pre-heated combustion chamber (CC), to validate the fuel consumption reduction, compared to an actual and commercial device, used on air models.展开更多
True triaxial rockburst experiments with four different unloading rates were performed on four prism specimens of granite sampled from Beishan, China. The damage evolution in the rockburst test was investigated from t...True triaxial rockburst experiments with four different unloading rates were performed on four prism specimens of granite sampled from Beishan, China. The damage evolution in the rockburst test was investigated from two aspects including fracture surface crack and fragment characteristics. The scanning electron microscopy was used to observe the micro crack information on fragment surface. Combing binarization and box counting dimensions, the fractal dimensions of cracks were obtained. Meanwhile,the fragments were collected and a sieving experiment was conducted. We weighed the fragments qualities, counted the amount of fragments and measured the fragments length, width and thickness.Utilizing four methods to calculate damage fractal dimensions of fragments, the trend of fractal value changing with unloading rates can be roughly described. It can be concluded from these experiments that the fractal dimension either for crack or for fragment holds a decreasing trend with the decreasing unloading rate, indicating a reduction of damage level.展开更多
基金funded by National Key R&D Program of China(Grant No.2023YFC3007001)Beijing Natural Science Foundation(Grant No.8244053)China Postdoctoral Science Foundation(Grant No.2024M754065).
文摘The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analysis scheme is proposed in this paper to investigate the soil deformation behavior under the coupling of stress and drying-wetting cycles.A new device is developed based on CT(computerized tomography)workstation to apply certain normal and shear stresses on a soil specimen during drying-wetting cycles.A series of tests are conducted on a type of loess with various coupling of stress paths and drying-wetting cycles.At macroscopic level,stress sensor and laser sensor are used to acquire stress and strain,respectively.The shear and volumetric strain increase during the first few drying-wetting cycles and then become stable.The increase of the shear stress level or confining pressure would cause higher increase rate and the value of shear strain in the process of drying-wetting cycles.At microscopic level,the grayscale value(GSV)of CT scanning image is characterized as the proportion of soil particles to voids.A fabric state parameter is proposed to characterize soil microstructures under the influence of stress and drying-wetting cycle.Test results indicate that the macroand micro-responses show high consistence and relevance.The stress and drying-wetting cycles would both induce collapse of the soil microstructure,which dominants degradation of the soil mechanical properties.The evolution of the macro-mechanical property of soil exhibits a positive linear relationship with the micro-evolution of the fabric state parameter.
文摘The relation of mass, stiffness and rate of damping is obtained by using the mechanical analysis of the obstructive vibration system of two dimensions for the design of the obstructive vibration system of more freedom and the micro vibration test bed. The result of stimulational experiment indicates that the isolation of vibration of this system is satisfactory. The design method of vibration can be used as the reference to ultra precision machine tool, super micro orientation machanism and so on.
文摘Objective To test Calcium ion(Ca2+) flow at the head and end of outer hair cells(OHCs) in resting state and in response to Nimodipine treatment.Methods Non-invasive micro-test techniques were used to study Ca2+ in isolated OHCs in adult guinea pigs.Results Four types of Ca2+ transport were identified in OHCs on basilar membrane tissue fragments:influx at the head of with efflux at the bottom(type 1):efflux at the head of OHCs with influx at the bottom(type 2);influx at the both head and bottom(type 3);and efflux at the both head and bottom(type 4).However,only type 1 and type 3 of Ca2+ ion transport were detected in the cochlea.We propose that Ca2+ ion transport exists in adult guinea pig cochlear OHCs in resting state and is variable.Ca2 + flow in OHC can be inhibited by Nimodipine in resting state.
文摘A micro shear testing method which can suit to measure the mechanical properties of heterogeneous materials is introduced, and the properties in each zone of welded joint for CO2 arc welding can be evaluated by using this method in this paper. Moreover, these results are compared with those results of Charpy V-notch impact test and their correlation is discussed.
文摘Toarcian claystone such as that of the Callovo-Oxfordian is a qualified multiphase material. The claystone samples tested in this study are composed of four main mineral phases: silicates(clay minerals, quartz,feldspars, micas)(z86%), sulphides(pyrite)(z3%), carbonates(calcite, dolomite)(z10%) and organic kerogen(z1%). Three sets of measurements of the modulus of deformability were compared as determined in(i) nanoindentation tests with a constant indentation depth of 2 mm,(ii) micro-indentation tests with a constant indentation depth of 20 mm, and(iii) meso-compression tests with a constant displacement of 200 mm. These three experimental methods have already been validated in earlier studies. The main objective of this study is to demonstrate the influence of the scaling effect on the modulus of deformability of the material. Different frequency distributions of the modulus of deformability were obtained at the different sample scales:(i) in nano-indentation tests, the distribution was spread between 15 GPa and 90 GPa and contained one peak at34 GPa and another at 51 GPa;(ii) in the micro-indentation tests, the distribution was spread between 25 GPa and 60 GPa and displayed peaks at 26 GPa and 37 GPa; and(iii) in the meso-compression tests, a narrow frequency distribution was obtained, ranging from 25 GPa to 50 GPa and with a maximum at around 35 GPa.
文摘Based on three kinds of dynamic test of MEMS, a dynamic system for the vibration test of micro machined gyroscope based on high speed photography is introduced. Firstly, the architecture of the system hardware is introduced. Secondly, the image tracking performance is compared by the test using the template matching algorithm, the mean shift algorithm and the SURF algorithm. The vibration curve shows that high speed photograph combined with SURF algorithm is faster, more ac- curate, and more suitable for the vibration test of micro machined gyroscope. After the frequency a- nalysis and related interpolation, more characteristics of micro gyroscope can be obtained.
基金Supported by the National Natural Science Fundation of China(61174219)
文摘To measure projectile attitude in space flight, based on continuous wave （CW） radar, a new micro-Doppler effect testing technique is developed in this paper. It also establishes radar testing model for attitude of flying projectile and resolve micro-Doppler effect of projectile motion attitude. By distinguishing and geting attitude parameters such as micro-motion period, this technique can in- tuitively estimate the flight stability of projectile, and the validity of this technique is proved accord- ing to flight tests.
基金the National Natural Science Foundation of China (No. 50171026)the Natu-ral Science Foundation of Heilongjiang Province, China (No. E2007-36).
文摘Ceramic coatings were prepared on Ti-6Al-4V alloy in NaAlO2 solution by micro-plasma oxidation （MPO）. The salt spray tests of the coated samples and the substrates were carded out in a salt spray test machine. The phase composition and surface morphology of the coatings were investigated by XRD and SEAM. Severe corrosion occurred on the substrate surface, while there were no obvious corrosion phenomena on the coated samples. The coatings were composed of Al2TiO5 and a little α-Al2O3 and mille TiO2, and the salt spray test did not change the composition of the coatings. The weight loss rate of the coatings decreased with increasing MPO time because of the increase in density and thickness of the coatings. The surface morphology of the coatings was influenced by salt spray corrosion test. Among the coated samples, the coating prepared for 2 h has the best corrosion resistance under salt spray test.
文摘Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenient for micro power generation (5 - 30 kW) is because of their heaviness. Micro and ultra micro gas turbine devices, based on a micro compressor and a micro turbine installed on the same shaft, are more suitable for this scope for several reasons. Micro turbine systems have many advantages over reciprocating engine generators, such as higher power density (with respect to size and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. Micro turbines also have the advantage of having the majority of their waste heat contained in their relatively high temperature exhaust. Micro turbines offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels. The object of this study is the experimental tests on a stand-alone gas turbine device with a pre-heated combustion chamber (CC), to validate the fuel consumption reduction, compared to an actual and commercial device, used on air models.
基金supported by the National Key Basic Research Program (No. 2010CB226800)the Innovation Team Development Program of the Ministry of Education (No. IRT0656)the Fundamental Research Funds for the Central Universities (No. 2010YL14)
文摘True triaxial rockburst experiments with four different unloading rates were performed on four prism specimens of granite sampled from Beishan, China. The damage evolution in the rockburst test was investigated from two aspects including fracture surface crack and fragment characteristics. The scanning electron microscopy was used to observe the micro crack information on fragment surface. Combing binarization and box counting dimensions, the fractal dimensions of cracks were obtained. Meanwhile,the fragments were collected and a sieving experiment was conducted. We weighed the fragments qualities, counted the amount of fragments and measured the fragments length, width and thickness.Utilizing four methods to calculate damage fractal dimensions of fragments, the trend of fractal value changing with unloading rates can be roughly described. It can be concluded from these experiments that the fractal dimension either for crack or for fragment holds a decreasing trend with the decreasing unloading rate, indicating a reduction of damage level.
