陶瓷纳米颗粒在生物医学中的应用进展

近年来,纳米技术成为科学技术领域最重要与最激动人心的前沿领域之一.随着纳米技术的发展,纳米材料在生产和生活的各方面发挥着越来越重要的作用.陶瓷纳米颗粒作为一类重要的纳米材料,拥有体积效应、介电限域效应、量子尺寸效应和量子隧道效应等,使其在生物医学领域具有广阔的应用前景.本文综述了羟基磷灰石、磷酸钙、氧化铁、氧化锌和氧化铈陶瓷纳米颗粒的特点及其在肿瘤成像与治疗、骨组织工程和安全评价等生物医学领域的应用进展,并对陶瓷纳米颗粒在生物医学中的发展提出了几点建议.     

基于模型预测控制算法的多风储直流微电网分布式电压二次控制策略

针对含多组风储单元的直流微电网中蓄电池的电压优化控制问题,提出了一种基于模型预测控制算法的分布式电压二次控制策略.设计了一种多步长预测一致性模型作为电压预测模型,通过目标函数最小化求解预测系数,得到最优电压二次控制补偿量加入一次控制中,将传统一致性算法中比例积分控制器下的偏差调节问题转化为模型预测控制器下的电压跟踪问题进行求解,从而实现对直流母线电压动态响应的滚动优化.该方法有效解决了传统一致性算法下电压控制策略瞬态特性差和部分工况下存在控制误差等问题,并通过MATLAB/Simulink仿真平台搭建模型验证了不同工况下所提策略的有效性和优越性.     

水泥回转窑系统新型锚固件的制作和应用

耐热钢锚固件是支撑热工设备耐火材料内衬的骨架,以增强耐火材料内衬抵抗静荷载、热应力、机械膨胀、机械振动,适用于所有干法生产线的浇注料施工,在高温窑炉中有广泛的应用。传统锚固件制作主要包括钢筋剪断、冲压、焊接、装套等工序,工序复杂且不满足现今环保要求,本文通过对新型炉窑锚固件的设计、生产和使用情况对比分析,新型锚固件完全可以替代传统锚固件,且提高了生产效率,实现了清洁生产和零排放。     

Effects of Ultrasonic Vibration on Material Flow and Thermal Cycles in Friction Stir Welding of Dissimilar Al/Mg Alloys

Comparative experiments are performed in friction stir welding (FSW) of dissimilar Al/Mg alloys with and without assistance of ultrasonic vibration. Metallographic characterization of the welds at transverse cross sections reveals that ultrasonic vibration induces differences in plastic material flow in two conditions. In FSW, the plastic material in the peripheral area of shoulder-affected zone (SAZ) tends to flow downward because of the weakening of the driving force of the shoulder, and a plastic material insulation layer is formed at the SAZ edge. When ultrasonic vibration is exerted, the stirred zone is divided into the inner and outer shear layers, the downward material flow trend of the inner shear layer disappears and tends to flow upward, and the onion-ring structure caused by the swirl motion is avoided in the pin-affected zone. By improving the flow behavior of plastic materials in the stirred zone, ultrasonic vibration reduces the heat generation, accelerates the heat dissipation in nugget zone and changes the thermal cycles, thus inhibiting the formation of intermetallic compound layers.

     

Mold-filling characteristics of AZ91 magnesium alloy in the low-pressure expendable pattern casting process

The magnesium (Mg) alloy low-pressure expendable pattern casting (EPC) process is a newly developed casting technique combining the advantages of both EPC and low-pressure casting. In this article, metal filling and the effect of the flow quantity of inert gas on the filling rate in the low-pressure EPC process are investigated. The results showed that the molten Mg alloy filled the mold cavity with a convex front laminar flow and the metal-filling rate increased significantly with increasing flow quantity when flow quantity was below a critical value. However, once the flow quantity exceeded a critical value, the filling rate increased slightly. The influence of the flow quantity of inert gas on melt-filling rate reveals that the mold fill is controlled by flow quantity for a lower filling rate, and, subsequently, controlled by the evaporation of polystyrene and the evaporation products for higher metal velocity. Meanwhile, the experimental results showed that the melt-filling rate significantly affected the flow profile, and the filling procedure for the Mg alloy in the low-pressure EPC process. A slower melt-filling rate could lead to misrun defects, whereas a higher filling rate results in folds, blisters, and porosity. The optimized filling rate with Mg alloy casting is 140 to 170 mm/s in low-pressure EPC.     

甲醇合成塔用 150 mm SA387Gr22C12 钢板组织和力学性能

对 150 mm 厚 SA387Gr22C12 钢板( / % : 0．13 ～0．14C,0．09Si,0．55 ～0．56Mn,0．004P,0．001S,2．48 ～2． 49Cr,1．11～1．12Mo) 模拟焊后拉伸性能、－29 ℃ 冲击性能、金相组织及回火脆化倾向评定等进行试验,并检测了交货态(正火 + 回火) 、最小模拟焊后态、最大模拟焊后态及步冷试验后的钢板各项性能指标 。结果表明,钢板的回火脆化 倾向不明显,其结果 CvTr55 + 2．5ΔCvTr55 为－63 ℃,完全满足甲醇合成塔用钢板的技术要求。     

非晶金属丝的电磁性能及其在传感技术中的应用

非晶金属丝具有高的机械强度和优异的电磁特性。利用这些性能，可以用它制作各种传感器件。尤其，Ｆｅ基非晶丝存在大的巴克豪森和迈悌欧斯效应，是无颤动尖锐脉冲电动势发生器件材料。Ｃｏ－Ｆｅ基非晶丝具有零磁致伸缩效应。两类非晶金属丝主要被应用到制作传感器方面。非晶金属丝以它的圆截面形状，可高度集成的优点正在引进电子仪表进行的兴趣。     

Zr替代Ti对Ti19．5V40Mn16．2Cr9．8Ni14．5合金的影响Ⅱ：电化学性能

在对合金微观结构和储氢性能研究的基础上，详细考察了少量Zr取代Ti对Ti19．5V40Mn16．2Cr9．8Ni14．5合金电化学性能的影响。通过观察电极的充放电行为，并结合EIS及多种极化曲线的分析结果，发现少量Zr对Ti的取代能够显著提高合金电极的实际电化学容量和循环稳定性，而且还能在一定程度上改善合金的电极动力学性能。对于这些性能的改善，从合金微观结构方面进行了解释。