钛金属表面活化处理及表面细胞响应特性

采用不同比例的氢氟酸(1％(质量分数)HF)与双氧水(30％(质量分数)H2O2)以及二者不同配比(1∶1、5∶1和1∶5)的混合溶液对钛金属表面进行处理,制备出具有不同拓扑结构的钛活性表面.用扫描电镜(SEM)、原子力显微镜(AFM)、接触角测试和X射线光电子能谱(XPS)等手段分别对各组样品的表面形貌、粗糙度、亲疏水性及表面化学组成变化等进行分析和表征.将各组样品分别与骨肉瘤细胞株(MG63)共培养,用SEM观察细胞形态变化,利用MTT比色法测定细胞增殖能力,通过体外细胞培养实验考察处理后的钛金属表面对MG63细胞形貌及增殖分化特性的影响.结果表明,经HF和H2O2混合溶液处理后的样品表面粗糙,并含有丰富的F-和OH-基团,促进了细胞的粘附、铺展、生长和增殖,大幅改善了钛表面的生物活性.其中,氢氟酸与双氧水按1∶5配比的混合溶液处理后的样品在细胞培养前期显示出更加优良的细胞相容性,这对促进钛种植体与周围骨组织间的快速整合具有积极意义.     

插销法研究自保护焊U75V钢轨的冷裂敏感性

采用插销试验法研究了JDHS-38#自保护药芯焊丝焊接U75V钢轨的冷裂敏感性,评估了预热温度、线能量、焊道数3个因素对U75V钢轨临界断裂应力的影响.结果表明,现场对钢轨施焊时,采取250℃的预热温度,14 kJ/cm左右的线能量,双层焊等措施可以使钢轨接头热影响区少产生甚至不产生焊接冷裂纹,使其临界断裂应力达646 MPa,与抗拉强度相当.若采用其他工艺参数,临界断裂应力较低,且当拘束拉伸应力高于抗拉强度时,于热影响区发生氢致断裂.焊接接头过热区组织主要为马氏体、贝氏体,断口显微形貌主要为河流花样、泥状花样及爪状花样.     

UHF频段高功率SiC SIT

采用导通SiC衬底上的SiC多层外延材料,成功制作出了国内首个SiC SIT(静电感应晶体管).该器件研制中,采用了自对准工艺、高能离子注入及高温退火工艺、密集栅深凹槽干法刻蚀工艺、PECVD SiO:和SizNy介质钝化工艺,有效抑制了漏电并提高了器件击穿电压,器件功率输出能力由此得到提升.最终28 cm栅宽SiC ...     

Folded Architecture for Digital Gammatone Filter Used in Speech Processor of Cochlear Implant

Emerging trends in the area of digital very large scale integration (VLSI) signal processing can lead to a reduction in the cost of the cochlear implant. Digital signal processing algorithms are repetitively used in speech processors for filtering and encoding operations. The critical paths in these algorithms limit the performance of the speech processors. These algorithms must be transformed to accommodate processors designed to be high speed and have less area and low power. This can be realized by basing the design of the auditory filter banks for the processors on digital VLSI signal processing concepts. By applying a folding algorithm to the second‐order digital gammatone filter (GTF), the number of multipliers is reduced from five to one and the number of adders is reduced from three to one, without changing the characteristics of the filter. Folded second‐order filter sections are cascaded with three similar structures to realize the eighth‐order digital GTF whose response is a close match to the human cochlea response. The silicon area is reduced from twenty to four multipliers and from twelve to four adders by using the folding architecture.     

Development of weft‐knitted and braided polypropylene stents for arterial implant

Textile biomedical materials have been used for various applications contributing considerably in improving quality of life. The current study aims at improving polypropylene fibre stents which may replace metallic ones. In order to produce the stents, weft‐knitting and braiding technologies were used. In the braiding technique, by varying the take‐up ratio (using gears with the appropriate number of teeth in the braiding machine), it was possible to manufacture regular braids with angles of 65°, 70° and 75° in order to obtain different covers. In the knitting technique, a circular machine was used and the tightness of the structure was adjusted by varying the loop length and thus the fabric loop density, resulting in variations of the sample diameter. The knitting machine had negative feed, and so loop length variations were achieved by varying the yarn input tension, the stitch cam settings and the fabric take‐down tension. The samples were heat set. Yarns were contracted by setting at 130°C and 140°C, and this led to increasing the loop density and the flexural rigidity of the samples. A high cover of the samples resulted in a greater stiffness of the structures. The stents were evaluated by undertaking the tests required for arterial support: rigidity to radial compression, resistance to tensile forces and bending rigidity. The best results were obtained with braided structures. Future work may concentrate in improving the stent design and using new biocompatible fibres.     

声表面波器件测量牙种植体微扭矩的三维有限元仿真

为了利用微扭矩准确、非破坏性地测量牙种植体的稳定性,采用三维有限元分析方法研究了声表面波器件(SAW)检测牙种植体稳定性的可行性.首先,在梯度剪切应力场下建立了SAW器件的谐振频率和扭矩之间的理论模型.然后,利用ANSYS有限元软件对梯度剪切应力场下SAW器件的谐振频率变化情况进行谐振响应分析.最后,对比分析了理论模型和仿真得到的数据.分析结果表明:SAW器件谐振频率的变化量与最大剪切应力呈线性关系,但两者之间存在3％的误差;种植体的微扭矩与SAW器件的谐振频率呈线性关系.因此,在理论上能够利用SAW器件测量种植体的微扭矩,从而实现对种植体稳定性的检测.     

Energy harvesting by implantable abiotically catalyzed glucose fuel cells

Implantable glucose fuel cells are a promising approach to realize an autonomous energy supply for medical implants that solely relies on the electrochemical reaction of oxygen and glucose. Key advantage over conventional batteries is the abundant availability of both reactants in body fluids, rendering the need for regular replacement or external recharging mechanisms obsolete. Implantable glucose fuel cells, based on abiotic catalysts such as noble metals and activated carbon, have already been developed as power supply for cardiac pacemakers in the late-1960s. Whereas, in vitro and preliminary in vivo studies demonstrated their long-term stability, the performance of these fuel cells is limited to the μW-range. Consequently, no further developments have been reported since high-capacity lithium iodine batteries for cardiac pacemakers became available in the mid-1970s. In recent years research has been focused on enzymatically catalyzed glucose fuel cells. They offer higher power densities than their abiotically catalyzed counterparts, but the limited enzyme stability impedes long-term application. In this context, the trend towards increasingly energy-efficient low power MEMS (micro-electro-mechanical systems) implants has revived the interest in abiotic catalysts as a long-term stable alternative. This review covers the state-of-the-art in implantable abiotically catalyzed glucose fuel cells and their development since the 1960s. Different embodiment concepts are presented and the historical achievements of academic and industrial research groups are critically reviewed. Special regard is given to the applicability of the concept as sustainable micro-power generator for implantable devices.     

可降解镁合金材料的研究新进展

可降解镁合金材料因力学性能佳、生物相容性好以及可降解吸收等特点在植入材料领域成为研究热点。综述了可降解镁合金材料作为心血管支架、骨固定材料和多孔修复材料等的最新研究进展,阐述了其在体内的降解机理以及通过高纯镁合金开发、合金化、表面处理和快速凝固工艺等方法提高镁合金材料耐体液腐蚀性能,指出了目前可降解镁合金材料研究需要解决的问题和未来研究方向,并展望了其今后的临床应用前景。     

钉子植入木材的力学特性试验

通过分析钉子植入木材的过程,确定力学特性试验的方法,依据此方法设计试验装置并进行钉子对木材植入的力学特性试验。通过对试验结果相关数据的处理和分析,得出木材在钉子植入其内的过程中的力学特性,体现为一定的阻尼性和弹性。     

控轧控冷Q460高强钢焊接裂纹敏感性研究

对控扎控冷Q460高强钢进行了成分分析和组织观察,在此基础上利用经验公式评价了其热裂纹和再热裂纹敏感性,采用插销试验方法评定了其冷裂纹敏感性。研究结果表明,控扎控冷Q460高强钢降低了碳等合金元素含量,通过晶粒细化提高强度,显著降低了焊接热裂纹和再热裂纹敏感性。该钢的冷裂纹敏感性很小,可以不预热焊接。