Rock physics modeling is implemented for shales in the Luojia area of the Zhanhua topographic depression. In the rock physics model, the clay lamination parameter is introduced into the Backus averaging theory for the...Rock physics modeling is implemented for shales in the Luojia area of the Zhanhua topographic depression. In the rock physics model, the clay lamination parameter is introduced into the Backus averaging theory for the description of anisotropy related to the preferred alignment of clay particles, and the Chapman multi-scale fracture theory is used to calculate anisotropy relating to the fracture system. In accordance with geological features of shales in the study area, horizontal fractures are regarded as the dominant factor in the prediction of fracture density and anisotropy parameters for the inversion scheme. Results indicate that the horizontal fracture density obtained has good agreement with horizontal permeability measured from cores, and thus confirms the applicability of the proposed rock physics model and inversion method. Fracture density can thus be regarded as an indicator of reservoir permeability. In addition, the anisotropy parameter of the P-wave is higher than that of the S-wave due to the presence of horizontal fractures. Fracture density has an obvious positive correlation with P-wave anisotropy, and the clay content shows a positive correlation with S-wave anisotropy, which fully shows that fracture density has a negative correlation with clay and quartz contents and a positive relation with carbonate contents.展开更多
In order to investigate the mechanical response of reflective cracking in asphalt concrete pavement under dynamic vehicle loading, a finite element model is established in ABAQUS. The viscoelastic behavior is describe...In order to investigate the mechanical response of reflective cracking in asphalt concrete pavement under dynamic vehicle loading, a finite element model is established in ABAQUS. The viscoelastic behavior is described by a prony series which is calculated through nonlinear fitting to the creep test data obtained in the laboratory. Based on the viscoelastic theory, the time-temperature equivalence principle, fracture mechanics and the dynamic finite element method, both the Jintegral and the mix-mode stress intensity factor are utilized as fracture evaluation parameters, and a half-sine dynamic loading is used to simulate the vehicle loading. Finally, the mechanical response of the pavement reflective cracking is analyzed under different vehicle speeds, different environmental conditions and various damping factors. The results indicate that increasing either the vehicle speed or the structure damping factor decreases the maximum values of fracture parameters, while the structure temperature has little effect on the fracture parameters. Due to the fact that the vehicle speed can be enhanced by improving the road traffic conditions, and the pavement damping factor can become greater by modifying the components of materials, the development of reflective cracking can be delayed and the asphalt pavement service life can be effectively extended through both of these ways.展开更多
Samples of hot break tomato paste were collected from commercially produced aseptic totes after 6-11 months of storage at ambient temperature. Serum viscosity of the hot break tomato paste samples was analyzed at each...Samples of hot break tomato paste were collected from commercially produced aseptic totes after 6-11 months of storage at ambient temperature. Serum viscosity of the hot break tomato paste samples was analyzed at each sampling time and compared to the initial serum viscosity measured at the time of tomato paste manufacturing. As storage time increased, the serum viscosity of hot break tomato paste significantly decreased. After 7 months of storage, 16%-27% reduction of serum viscosity was observed in the hot break tomato paste. To evaluate effects of a heating on the serum viscosity of hot break tomato paste, the paste samples were reconstituted with water to 10° Brix, similar level of tomato solids in typical tomato sauce products. Diluted tomato paste was heated and held at 95℃ for 3 minutes and its serum viscosity was measured. After the heating, the serum viscosity of hot break tomato paste was slightly increased up to 5% of initial value, however the recovery was not significant （p 〈 0.05）.展开更多
A mechanical model of a fracturing viscoelastic material was developed to investigate viscous effects in a dynamically growing crack-tip field. It was shown that in the stable creep-growing phase, elastic deformation ...A mechanical model of a fracturing viscoelastic material was developed to investigate viscous effects in a dynamically growing crack-tip field. It was shown that in the stable creep-growing phase, elastic deformation and viscous deformation are equally dominant in the near-tip field, and stress and strain have the same singularity, namely, （σ-e）∝r^-1/（n-1）. The asymptotic solution of separating variables of stress, stain and displacement in the crack-tip field was obtained by asymptotic analysis, and the resulting numerical value of stress and strain in the crack-tip field was obtained by the shooting method and the boundary condition of a mode I crack. Through numerical calculation, it was shown that the near-tip fields are mainly governed by the creep exponent n and Mach number M. When n →∞, the asymptotic solution of a viscoelastic material can be degenerated into that of Freund＇s elastic-ideally plastic material by analyzing basic equations.展开更多
Adopting an elastic-viscoplastic, the asymptotic problem of mode I propagat ing crack-tip field is investigated. Various asymptotic solutions resulting from the analysis of crack growing programs are presented. The an...Adopting an elastic-viscoplastic, the asymptotic problem of mode I propagat ing crack-tip field is investigated. Various asymptotic solutions resulting from the analysis of crack growing programs are presented. The analysis results show that the quasi-statically growing crack solutions are the special case of the dynamic propagating solutions. Therefore these two asymptotic solutions can be unified.展开更多
Objective： The use of fibrin adhesives has a broad background in nerve repair. Currently the suboptimal physical properties of singledonor fibrin adhesives have restricted their usage. The present experiment studies ...Objective： The use of fibrin adhesives has a broad background in nerve repair. Currently the suboptimal physical properties of singledonor fibrin adhesives have restricted their usage. The present experiment studies the performance and physical characteristics of a modified fibrin glue prepared from single-donor human plasma in the repair of posterior tibial nerve of rat. Methods： Forty Wistar rats were divided into 5 groups; in the control group, tibial nerve was completely transected and no treatment was done, while in the four experimental groups the nerve stumps were reconnected by one suture, three sutures, one suture with fibrin glue and fibrin glue alone respectively. During 8 weeks of follow-up, Tibial Function Index was measured weekly and adhesive strength, inflammation and scar formation were assessed at the end of the study. Results： Nerve stumps dehiscence rate and adhesive strength were similar in all experimental groups and significantly differed from control group （P〈0.05）. By the end of the eighth follow-up week, functional recovery of one and three sutures groups were significantly higher than groups in which fibrin glue was used for repair （P〈0.05）. The amount of inflammation and scar tissue formation was similar among all groups. Conclusion： The study results show that the prepared single-donor fibrin adhesive has acceptable mechanical properties which could provide required adhesiveness and hold nerve stumps in the long term; yet, we acknowledge that more studies are needed to improve functional outcome ofsinszle donor fibrin adhesive repair.展开更多
基金sponsored by the National Natural Science Foundation of China under Grants 41404090,U1262208,and U1663207the Foundation of the Sino PEC Key Laboratory of Shale Oil/Gas Exploration and Production Technology under Grants No.G5800-15-ZS-WX039the project under Grants No.G5800-15-ZS-WX004
文摘Rock physics modeling is implemented for shales in the Luojia area of the Zhanhua topographic depression. In the rock physics model, the clay lamination parameter is introduced into the Backus averaging theory for the description of anisotropy related to the preferred alignment of clay particles, and the Chapman multi-scale fracture theory is used to calculate anisotropy relating to the fracture system. In accordance with geological features of shales in the study area, horizontal fractures are regarded as the dominant factor in the prediction of fracture density and anisotropy parameters for the inversion scheme. Results indicate that the horizontal fracture density obtained has good agreement with horizontal permeability measured from cores, and thus confirms the applicability of the proposed rock physics model and inversion method. Fracture density can thus be regarded as an indicator of reservoir permeability. In addition, the anisotropy parameter of the P-wave is higher than that of the S-wave due to the presence of horizontal fractures. Fracture density has an obvious positive correlation with P-wave anisotropy, and the clay content shows a positive correlation with S-wave anisotropy, which fully shows that fracture density has a negative correlation with clay and quartz contents and a positive relation with carbonate contents.
文摘In order to investigate the mechanical response of reflective cracking in asphalt concrete pavement under dynamic vehicle loading, a finite element model is established in ABAQUS. The viscoelastic behavior is described by a prony series which is calculated through nonlinear fitting to the creep test data obtained in the laboratory. Based on the viscoelastic theory, the time-temperature equivalence principle, fracture mechanics and the dynamic finite element method, both the Jintegral and the mix-mode stress intensity factor are utilized as fracture evaluation parameters, and a half-sine dynamic loading is used to simulate the vehicle loading. Finally, the mechanical response of the pavement reflective cracking is analyzed under different vehicle speeds, different environmental conditions and various damping factors. The results indicate that increasing either the vehicle speed or the structure damping factor decreases the maximum values of fracture parameters, while the structure temperature has little effect on the fracture parameters. Due to the fact that the vehicle speed can be enhanced by improving the road traffic conditions, and the pavement damping factor can become greater by modifying the components of materials, the development of reflective cracking can be delayed and the asphalt pavement service life can be effectively extended through both of these ways.
文摘Samples of hot break tomato paste were collected from commercially produced aseptic totes after 6-11 months of storage at ambient temperature. Serum viscosity of the hot break tomato paste samples was analyzed at each sampling time and compared to the initial serum viscosity measured at the time of tomato paste manufacturing. As storage time increased, the serum viscosity of hot break tomato paste significantly decreased. After 7 months of storage, 16%-27% reduction of serum viscosity was observed in the hot break tomato paste. To evaluate effects of a heating on the serum viscosity of hot break tomato paste, the paste samples were reconstituted with water to 10° Brix, similar level of tomato solids in typical tomato sauce products. Diluted tomato paste was heated and held at 95℃ for 3 minutes and its serum viscosity was measured. After the heating, the serum viscosity of hot break tomato paste was slightly increased up to 5% of initial value, however the recovery was not significant （p 〈 0.05）.
基金Supported by the Nature foundation of Heilongjiang Province under Grant No. A009 the foundation of Harbin Engineering University under Grant No. HEUF04005.
文摘A mechanical model of a fracturing viscoelastic material was developed to investigate viscous effects in a dynamically growing crack-tip field. It was shown that in the stable creep-growing phase, elastic deformation and viscous deformation are equally dominant in the near-tip field, and stress and strain have the same singularity, namely, （σ-e）∝r^-1/（n-1）. The asymptotic solution of separating variables of stress, stain and displacement in the crack-tip field was obtained by asymptotic analysis, and the resulting numerical value of stress and strain in the crack-tip field was obtained by the shooting method and the boundary condition of a mode I crack. Through numerical calculation, it was shown that the near-tip fields are mainly governed by the creep exponent n and Mach number M. When n →∞, the asymptotic solution of a viscoelastic material can be degenerated into that of Freund＇s elastic-ideally plastic material by analyzing basic equations.
文摘Adopting an elastic-viscoplastic, the asymptotic problem of mode I propagat ing crack-tip field is investigated. Various asymptotic solutions resulting from the analysis of crack growing programs are presented. The analysis results show that the quasi-statically growing crack solutions are the special case of the dynamic propagating solutions. Therefore these two asymptotic solutions can be unified.
文摘Objective： The use of fibrin adhesives has a broad background in nerve repair. Currently the suboptimal physical properties of singledonor fibrin adhesives have restricted their usage. The present experiment studies the performance and physical characteristics of a modified fibrin glue prepared from single-donor human plasma in the repair of posterior tibial nerve of rat. Methods： Forty Wistar rats were divided into 5 groups; in the control group, tibial nerve was completely transected and no treatment was done, while in the four experimental groups the nerve stumps were reconnected by one suture, three sutures, one suture with fibrin glue and fibrin glue alone respectively. During 8 weeks of follow-up, Tibial Function Index was measured weekly and adhesive strength, inflammation and scar formation were assessed at the end of the study. Results： Nerve stumps dehiscence rate and adhesive strength were similar in all experimental groups and significantly differed from control group （P〈0.05）. By the end of the eighth follow-up week, functional recovery of one and three sutures groups were significantly higher than groups in which fibrin glue was used for repair （P〈0.05）. The amount of inflammation and scar tissue formation was similar among all groups. Conclusion： The study results show that the prepared single-donor fibrin adhesive has acceptable mechanical properties which could provide required adhesiveness and hold nerve stumps in the long term; yet, we acknowledge that more studies are needed to improve functional outcome ofsinszle donor fibrin adhesive repair.
