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Surface modification techniques have been applied to generate titanium implant surfaces that promote osseointegration for the implants in cementless arthroplasty. However, its effect is not sufficient for osteoporotic bone. Strontium (Sr) promotes osteoblast proliferation and inhibits osteoclast proliferation and positively affects bone regeneration. The aim of this study was to confirm the effects of strontium-substituted hydroxyapatite (Sr-HA) coating via electrochemical deposition on implant's osseointegration in the osteoporotic condition. Female Sprague Dawley rats were used for this study. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into four groups: group HA; group 5 % Sr-HA; group 10 % Sr-HA; and group 20 % Sr-HA. Afterward, all rats from groups HA, 5 % Sr-HA, 10 % Sr-HA, and 20 % Sr-HA received implants with hydroxyapatite coating containing 0, 5, 10, and 20 % Sr. Implants were inserted bilaterally in all animals until death at 12 weeks. The bilateral femurs of rats were harvested for evaluation. All treatment groups increased new bone formation around the surface of titanium rods and push-out force; group 20 % Sr-HA showed the strongest effects on new bone formation and biomechanical strength. Additionally, these are significant differences in bone formation and push-out force was observed between groups 5 % Sr-HA and 10 % Sr-HA. This finding suggests that Sr-HA coating can improve implant osseointegration, and the 20 % Sr coating exhibited the best properties for implant osseointegration among the tested coatings in osteoporosis rats. [ABSTRACT FROM AUTHOR]

Surface modification techniques have been applied to generate titanium implant surfaces that promote osseointegration for the implants in cementless arthroplasty. However, its effect is not sufficient for osteoporotic bone. Zinc (Zn), magnesium (Mg), and strontium (Sr) present a beneficial effect on bone growth, and positively affect bone regeneration. The aim of this study was to confirm the different effects of the fixation strength of Zn, Mg, Sr-substituted hydroxyapatite-coated (Zn-HA-coated, Mg-HA-coated, Sr-HA-coated) titanium implants via electrochemical deposition in the osteoporotic condition. Female Sprague–Dawley rats were used for this study. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into four groups: group HA; group Zn-HA; group Mg-HA and group Sr-HA. Afterwards, all rats from groups HA, Zn-HA, Mg-HA and Sr-HA received implants with hydroxyapatite containing 0%, 10% Zn ions, 10% Mg ions, and 10% Sr ions. Implants were inserted bilaterally in all animals until death at 12 weeks. The bilateral femurs of rats were harvested for evaluation. All treatment groups increased new bone formation around the surface of titanium rods and push-out force; group Sr-HA showed the strongest effects on new bone formation and biomechanical strength. Additionally, there are significant differences in bone formation and push-out force was observed between groups Zn-HA and Mg-HA. This finding suggests that Zn, Mg, Sr-substituted hydroxyapatite coatings can improve implant osseointegration, and the 10% Sr coating exhibited the best properties for implant osseointegration among the tested coatings in osteoporosis rats. [ABSTRACT FROM AUTHOR]

Viaducts with steel bearings are subject to damage during earthquakes. Damage to conventional steel bearings could cause viaduct decks to collapse. This study attempts to prevent large displacements by installing steel stoppers at both sides of roller bearings. Shock absorber devices (SADs) are also installed between roller bearings and stoppers to reduce pounding forces. The study then explores the effectiveness of different stopper gaps and SADs installed between roller bearings and stoppers in mitigating viaduct damage. The effectiveness of stoppers without and with SADs is also investigated. The pounding forces between roller bearings and stoppers, the displacements on the tops of piers, the displacements of superstructures, and the bending moment-curvature relationship at pier bases are evaluated accordingly. Numerical results reveal that earthquake damage to viaducts with small stopper gaps is not significant. The application of SADs is also found to significantly mitigate viaduct damage. [ABSTRACT FROM AUTHOR]

Abstract: This research is intended to develop a FEM-based riding comfort optimization approach to the railway trains considering the coupling effect of vehicle–track system. To obtain its accurate dynamic response, the car body is modeled with finite elements, while the bogie frames and wheel-sets are idealized as rigid bodies. The differential equations of motion of the dynamic vehicle–track system are derived considering wheel–track interaction, in which the pseudo-excitation method and the symplectic mathematical method are effectively applied to simplify the calculation. Then, the min–max optimization approach is utilized to improve the train riding comfort with related parameters of the suspension structure adopted as design variables, in which 54 design points on the car floor are chosen as estimation locations. The K–S function is applied to fit the objective function to make it smooth, differentiable and have superior integrity. Analytical sensitivities of the K–S function are then derived to solve the optimization problem. Finally, the effectiveness of the proposed approach is demonstrated through numerical examples and some useful discussions are made. [Copyright &y& Elsevier]