羽毛球场斜屋面高架支撑设计与施工

本文通过对综合楼内羽毛球场斜屋面实施满堂高架支撑系统的设计与施工进行简要介绍,为屋面高倾斜、跨度大、单层净空高、大面积这一特殊结构施工课题研究提供借鉴经验。     

Non-occupational ladder and scaffold fall injuries

In the period 1988–1997 a series of 1462 patients aged 15 years or older with non-occupational fall injuries from ladders or scaffolds were studied. We registered 1402 ladder falls and 60 scaffold falls. The mean age was 50 years, and 1052 were males. The mean annual incidence rate was 1.18 per 1000 inhabitants/year for males and 0.41 per 1000 inhabitants/year for females. A rise in the annual incidence rates with increasing age were observed for both males and females, whereas no trend in the annual incidence rates for each of the ten years studied were observed. About 1/5 of the patients were hospitalized with a median number of 7 days. Two patients died following the injury. Half of the registered injuries were contusions or sprains, whereas about 1/3 were fractures or dislocations. The extremities were most commonly injured as 36% of the injuries were located to the lower extremities and 33% to the upper extremities. The forearm was most commonly fractured or dislocated, whereas the ankle joint was most commonly sprained or contused.     

Effects of microwave sintering on the properties of porous hydroxyapatite scaffolds

Microwave sintering was used to process porous hydroxyapatite scaffolds fabricated by the extrusion deposition technique. The effects of microwave sintering on the microstructure, phase composition, degradation, compressive strength and biological properties of the scaffolds were investigated. After rapid sintering, scaffolds with controlled structure, high densification and fine grains were obtained. A significant increase in mechanical strength was observed relative to conventional sintering. The scaffolds (55–60% porosity) microwave sintered at 1200 °C for 30 min exhibited the highest average compressive strength (45.57 MPa). The degradation was determined by immersing the scaffolds in physiological saline and monitoring the Ca²⁺concentration. The results indicated that the microwave-sintered scaffolds possessed higher solubility than conventionally sintered scaffolds, as it released more Ca²⁺ at the same temperature. Furthermore, an in vitro MC3T3-E1 cell culturing study showed significant cell adhesion, distribution, and proliferation in the microwave-sintered scaffolds. These results confirm that microwave sintering has a positive effect on the properties of porous hydroxyapatite scaffolds for bone tissue engineering applications.     

导轨式自升降脚手架遥控系统

本文介绍了一种新型的模块化自升降脚手架遥控系统,该系统采用无线遥控模块实现提升过程控制,克服了普通自升降脚手架控制系统控制器过大,控制不灵活的缺点.对系统进行了可靠性分析,给出了遥控器和提升控制器原理图,程序流程图.     

纳米磷灰石晶体/聚酰胺复合骨组织工程支架材料的研究

采用常压共溶、共沉淀和水热处理的方法制备了纳米磷灰石晶体／聚酰胺复合骨组织工程支架材料。纳米磷灰石在复合材料中含量高达60wt％(重量比),纳米磷灰石和聚酰胺之间有化学键结合,材料的力学性能接近自然骨水平。复合材料可加工成块状多孔体,材料的孔隙率为55％-70％,平均孔径为300μm,多孔支架不仅有大孔,而且大孔壁上含有丰富微孔,是一种非常有发展前景的组织工程材料。     

Direct ink writing of highly bioactive glasses

Direct ink writing (DIW), or Robocasting, is an additive manufacturing technique that offers the opportunity to create patient specific bioactive glass scaffolds and high strength scaffolds for bone repair. The original 45S5 Bioglass^® composition crystallises during sintering and until now, robocast glass scaffolds contained at least 51.9 mol% SiO₂ or B₂O₃ to maintain their amorphous structure. Here, ICIE16 and PSrBG compositions, containing <50 mol% SiO₂, giving silicate network connectivity close to that of 45S5, were robocast and compared to 13–93 composition. Results showed Pluronic F-127 can be used as a universal binder regardless of glass reactivity and that particle size distribution affected the ink “printability”. Scaffolds with interconnects of 150 μm (41–43% porosity) had compressive strengths of 32–48 MPa, depending on the glass composition. Robocast scaffolds from these highly reactive bioactive glasses promise greatly improved bone regeneration rates compared with existing bioactive glass scaffolds.     

β-TCP scaffold coated with PCL as biodegradable materials for dental applications

Requirements for an ideal scaffold include biocompatibility, biodegradability, mechanical strength and sufficient porosity and pore dimensions. Beta tricalcium phosphate (β-TCP) has competent biocompatibility and biodegradability, but has low mechanical strength because of its porous structure. Polycaprolactone (PCL) is a biodegradable polymer with elastic characteristics and good biocompatibility. In this study, β-TCP/PCL composites were prepared in different ratio and their morphology, phase content, mechanical properties, biodegradation and biocompatibility were investigated. After coating, surfaces of β-TCP scaffolds were covered with the PCL while some of the pores were partially clogged. The compression and bending strength of β-TCP scaffolds were significantly enhanced by PCL coating. The degradation rate of the scaffold in Tris buffer was reduced with higher content of the PCL coating. MTT and ALP assays showed that the osteoblast cells could proliferate and differentiate on PCL coated scaffolds as well as on bare β-TCP scaffolds. Based on the comprehensive analysis achieved in this study, it is concluded that the β-TCP/PCL composite scaffold fabricated with 40% β-TCP and 5% PCL exhibits optimum properties suitable for dental applications.     

Additive manufacturing of bioceramic scaffolds by combination of FDM and slip casting

Bioceramic scaffolds consisting of bioactive glasses or calcium phosphates have a high biocompatibility and are able to stimulate the ingrowth and regeneration of bone. For the production of these complex, highly porous structures, the additive manufacturing technologies are of particular importance. Normally, the image of the CAD model is printed directly. In this study, the indirect approach was chosen. The Fused Deposition Modeling (FDM) process was used to print thermoplastic molds, which were the negative of the ceramic to be produced. Subsequently, these molds were filled with ceramic slurries as in the slip casting process and the thermoplastic form was burnt out. The viscosity of the slurries as well as the thermal behaviour of the green bodies was characterized. The resulting bioceramic scaffolds have a filigree structure with moderate porosity. The compressive strength of these components is above the strength of cancellous bone.     

FEA evaluation of material stiffness changes for a polymer assisted 3D polycaprolactone/β-tricalcium phosphate scaffold in a mandibular defect reconstruction model

In bone regenerative engineering, the biomechanical performance of the scaffold at the bone-tissue interface is a key consideration. The evaluation of this parameter is a crucial step in designing, optimizing and manufacturing of bone substitute materials for clinical application, but is as yet comparatively unexplored. To this end, we utilized a novel polymer-assisted method to fabricate a three-dimensional (3D) Polycaprolactone/β-Tricalcium phosphate scaffold. The compressive modulus was measured and the data used to inform finite element analysis. The scaffolds achieved a maximum compressive moduli of 151 MPa, close to that of cortical bone. Further computational simulations were performed to determine the stresses and local scaffold adaptation profile, using data from computer tomography scans of the mandible. Local stresses were simulated based on the density changes in new bone forming in the scaffold at different stages of healing. The stress distribution in the mandible, scaffold center and scaffold interface were explored for a static load of 200 N, which corresponds to the load of adult mastication near the incisors. The analysis revealed that the maximum cross-sectional stress at the scaffold center and at the scaffold interface was 2.7 and 4.12 MPa respectively. The majority of the stress was localized in the bone of the mandible, with the scaffold bearing minimal loading at the start, but more over time as infiltration of more new bone progressed.