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81.
溶胶-凝胶生物玻璃多孔材料显微结构和生物活性的扫描电镜及红外光谱分析 总被引:13,自引:0,他引:13
本文利用溶胶.凝胶法制备了CaO-P2O5-SiO,系统生物活性玻璃,并以其为原料制备了用于骨修复及骨组织工程支架的块状生物活性材料。利用体外实验方法(invitro)结合x射线衍射(XRD)、扫描电子显微镜(SEM)和傅立叶变换红外光谱分析(FTIR)技术对不同烧结工艺制备的材料结构、晶相和生物活性的影响进行了分析研究。研究表明,经800℃和1100℃烧结5min的两种材料均有硅磷酸钙Ca5(PO4)2SjO4微晶相析出。烧结温度越高,析出微晶相的体积比例越大,材料的生物活性则越低。在模拟生理溶液中碳酸羟基磷灰石(HCA)只在烧结体中的玻璃颗粒表面形成,而在其硅磷酸钙Ca5(PO4)2SiO4微晶相表面未发现HCA形成。 相似文献
82.
In this paper, we propose an efficient design method for area optimization in a digital filter. The conventional methods to reduce the number of adders in a filter have the problem of a long critical path delay caused by the deep logic depth of the filter due to adder sharing. Furthermore, there is such a disadvantage that they use the transposed direct form (TDF) filter which needs more registers than those of the direct form (DF) filter. In this paper, we present a hybrid structure of a TDF and DF based on the flattened coefficients method so that it can reduce the number of flip‐flops and full‐adders without additional critical path delay. We also propose a resource sharing method and sharing‐pattern searching algorithm to reduce the number of adders without deepening the logic depth. Simulation results show that the proposed structure can save the number of adders and registers by 22 and 26%, respectively, compared to the best one used in the past. 相似文献
84.
Metal-based microelectromechanical systems (MEMS) have important advantages over Si-based MEMS. To form any functional metal-based
microdevice from metallic high-aspect-ratio microscale structures (HARMS), proper assembly and packaging are required. In
this paper, we report successful eutectic bonding of Al-based HARMS using Al–Ge intermediate layers. A series of Al–Ge composite
thin films were vapor deposited. Their composition and micro-/nano-scale structure were characterized. The morphology of bonded
Al structures was examined, including the morphology of separated surfaces. 相似文献
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C. T. Ho 《Journal of Materials Science》1996,31(21):5781-5786
Nickel and copper were deposited over brominated, surface treated, and pristine P-100 carbon fibres using cementation and electroplating techniques. The fibres were brominated by bromine vapour for 48 h and then desorbed at 200 °C in air for 12 h. The anodic oxidation treatment of the fibres involved electrochemical etching in a dilute sodium hydroxide electrolyte for 3 min. Electroplated coated fibres showed better tensile properties than cementation coated fibres. In addition, nickel coating exhibited better bonding with the carbon fibres compared to copper coating. The effect of bromination and surface treatment was improved adhesion between coating and fibres. Nickel- and copper-coated fibres, which were brominated, anodically oxidized, and pristine, reinforced tin-lead alloy composites were fabricated by squeeze casting. The composites containing coated treated carbon fibres had higher tensile and shear strength than the ones containing coated pristine carbon fibres. Moreover, the composite with coated brominated carbon fibres had better tensile strength and shear strength than the surface treatment. The results also showed the composites containing nickel-coated fibres had higher tensile and shear strength than the ones containing copper-coated fibres. 相似文献
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In multiple pregnancies, survival of remaining fetuses after premature death and delivery of one fetus is uncommon. We report a case of a triplet pregnancy that was reduced to twins at the 14th gestational week and then had preterm premature rupture of membranes and intrauterine fetal death of one twin at the 17th gestational week. To save the surviving fetus, delivery of the dead fetus and ligation of the umbilical cord at the cervical level were performed. We also performed McDonald cervical cerclage to keep the placenta of the dead fetus as well as that of the surviving one in the uterine cavity. After a series of aggressive procedures, including immediate administration of tocolytic agents, and antibiotic prophylaxis to prevent infection and preterm labor, the surviving fetus was delivered vaginally 73 days later due to intractable uterine contractions. After a 10-week hospital stay, the infant boy, weighing 2,500 g, was discharged without any sequelae. To our knowledge, this was the longest interval between deliveries in a triplet pregnancy reported in Taiwan. With adequate intensive management, a satisfactory outcome of the fetus and mother in such cases is possible. 相似文献