The physical properties of six type particleboards bonded with different formaldehydebased resins were tested. arer wetting and redrying, Uiree PF bonded boards retained much higher pro portion of their initial dry st...The physical properties of six type particleboards bonded with different formaldehydebased resins were tested. arer wetting and redrying, Uiree PF bonded boards retained much higher pro portion of their initial dry strength than the boards bonded with resins containing urea. The strength lossis the results of mechanical forces, caused by particle movement, breaking adhesive bonds.展开更多
Horizontal density variation is a structural phenomenon of non-veneer wood composites. The variation and distribution characteristics of horizontal density have impacts on the products properties. In this study, venee...Horizontal density variation is a structural phenomenon of non-veneer wood composites. The variation and distribution characteristics of horizontal density have impacts on the products properties. In this study, veneer strip simulated flake boards with 4 kinds of density distribution were made using a mat model. The density variation of the modeled mats was discussed, as well as the relationship between sample size and density variation. The effects of density and density distribution of non-veneer composites on the internal bond strength were analyzed. Result shows that the horizontal density of random formed particleboard follows normal distribution. Density has remarkable influence on internal bond strength (IB). Increasing density helps to improve IB at lower density stage, but has negative impacts on IB at higher density stage. Density variation between testing specimens depends on their sizes. Properly increasing specimen size can decrease the variation of the IBs.展开更多
Objective: To understand the relationship between porosity, collagen fiber orientation and strength of the plated bone after rigid plate fixation and removal. Methods: Seventy two New Zealand white rabbits were used i...Objective: To understand the relationship between porosity, collagen fiber orientation and strength of the plated bone after rigid plate fixation and removal. Methods: Seventy two New Zealand white rabbits were used in this experiment. Eight animals served as control and the other sixty four were plated on their intact left tibiae with stainless steel (316L) 4 hole plates to induce early osteoporosis. The plates were removed 2 months after internal fixation in 40 plated animals, 8 of which were sacrificed immediately following plate removal and the other 32 were killed in successive groups with 8 in each group 1,2,3 and 4 months after plate removal. The remaining 24 plated animals were killed at 3,4 and 6 months after plate fixation. After sacrifice, the samples of plated bone were prepared for light microscope, quantitative histological analysis, polarized light microscope and biomechanical test. Results: The internal fixation with a rigid plate could induce the regional osteoporosis which manifested both bone loss and disorganized bone structure (loss of the orientation of the collagen fibers) leading to decreased strength of the plated bone. Although the regional osteoporosis could recover gradually after plate removal, the bone structure remained disorderly even when the bone mass returned to normal. Delayed restoration of bone structure was related to delayed restoration of bone strength. Conclusions: Besides the bone loss, the disorganized bone structure is the main cause of decrease of bone strength after rigid plate fixation and removal.展开更多
文摘The physical properties of six type particleboards bonded with different formaldehydebased resins were tested. arer wetting and redrying, Uiree PF bonded boards retained much higher pro portion of their initial dry strength than the boards bonded with resins containing urea. The strength lossis the results of mechanical forces, caused by particle movement, breaking adhesive bonds.
文摘Horizontal density variation is a structural phenomenon of non-veneer wood composites. The variation and distribution characteristics of horizontal density have impacts on the products properties. In this study, veneer strip simulated flake boards with 4 kinds of density distribution were made using a mat model. The density variation of the modeled mats was discussed, as well as the relationship between sample size and density variation. The effects of density and density distribution of non-veneer composites on the internal bond strength were analyzed. Result shows that the horizontal density of random formed particleboard follows normal distribution. Density has remarkable influence on internal bond strength (IB). Increasing density helps to improve IB at lower density stage, but has negative impacts on IB at higher density stage. Density variation between testing specimens depends on their sizes. Properly increasing specimen size can decrease the variation of the IBs.
文摘Objective: To understand the relationship between porosity, collagen fiber orientation and strength of the plated bone after rigid plate fixation and removal. Methods: Seventy two New Zealand white rabbits were used in this experiment. Eight animals served as control and the other sixty four were plated on their intact left tibiae with stainless steel (316L) 4 hole plates to induce early osteoporosis. The plates were removed 2 months after internal fixation in 40 plated animals, 8 of which were sacrificed immediately following plate removal and the other 32 were killed in successive groups with 8 in each group 1,2,3 and 4 months after plate removal. The remaining 24 plated animals were killed at 3,4 and 6 months after plate fixation. After sacrifice, the samples of plated bone were prepared for light microscope, quantitative histological analysis, polarized light microscope and biomechanical test. Results: The internal fixation with a rigid plate could induce the regional osteoporosis which manifested both bone loss and disorganized bone structure (loss of the orientation of the collagen fibers) leading to decreased strength of the plated bone. Although the regional osteoporosis could recover gradually after plate removal, the bone structure remained disorderly even when the bone mass returned to normal. Delayed restoration of bone structure was related to delayed restoration of bone strength. Conclusions: Besides the bone loss, the disorganized bone structure is the main cause of decrease of bone strength after rigid plate fixation and removal.
