生物假体模型的快速成型制作技术

介绍了几种用于赝复体制作的快速成型方法,提出采用选区激光烧结成型快速制造医学假体,在人造五官医学假体特别是整容术赝复体的设计及制造方面,具有良好的应用前景,并采用选区激光烧结蜡粉得到赝复体原型蜡模,用于赝复体的快速制作。     

尼龙6/铜复合粉末选区激光烧结制件翘曲研究

通过大量的对尼龙6/铜复合尼龙粉末烧结试验,研究不同工艺参数,如激光功率、铺粉厚度以及扫描速度对制件翘曲程度的影响,并采用翘曲高度法来表征翘曲程度。根据试验数据绘出了尼龙制件翘曲程度随各工艺参数的变化曲线,总结出了制件翘曲程度随各工艺参数变化的趋势。     

频率选择表面A夹层雷达罩的传输特性

基于互导纳法设计了A夹层频率选择表面(FSS)罩壁结构并制作了平面试件和圆锥形雷达罩试件,验证了复合结构的一体化加工工艺。在微波暗室中对平板试件和FSS锥形罩进行了测试将部分测试结果与计算结果进行了比较。结果表明,A夹层加载的双层FSS带内传输损耗较小,具有一定的平顶特性,且带宽的入射角和极化稳定性较好。60°斜入射时,双层FSS的TE和TM极化的-3 dB带宽之差比相应单层FSS减小1.3 GHz;蜂窝夹芯层厚度较大时(1/4λ左右),A夹层两侧的单层FSS之间耦合较小,因而双层FSS的谐振频率与单层相同。曲面FSS雷达罩的传输特性与天线极化状态和测试方位均有关系,在主极化平面内与平面试件的结果一致,表明局部近场测试时曲率的影响较小,设计时可采取局部平面近似。     

Catalytic properties in deNOx and SO2–SO3 reactions

SCR-deNO_x reaction and SO₂–SO₃ oxidation tests were carried out by different research groups over fresh and used EUROCAT oxide samples in order to characterize the reactivity of the catalysts and to compare data obtained in several laboratories (Politecnico of Milan, Università of Salerno, ENEL of Milan, Boreskov Insitute of Catalysis).

Data are presented which indicate that the used EUROCAT catalyst is slightly more active both in the deNO_x reaction and SO₂–SO₃ oxidation than the fresh sample.

An analyses of data collected over honeycomb catalysts by means of a 2D, single-channel model of the SCR monolith reactor has been performed to evaluate the intrinsic kinetic constant of the deNO_x reaction; a satisfactory comparison has been obtained between estimation of the intrinsic kinetic constant and estimation of the intrinsic catalyst activity from data collected over powdered catalysts. A good agreement has been found in the experimental results collected in the different labs, both for the deNO_x reaction and SO₂–SO₃ oxidation.     

A new approach to study the gas-phase oxidation of toluene: probing active sites in vanadia-based catalysts under working conditions

Differently prepared vanadyl pyrophosphate and potassium-doped vanadia catalysts have been studied during the selective oxidation of toluene and p-methoxy toluene to the corresponding benzaldehydes using a portfolio of various in situ-methods (EPR, UV–VIS–DRS, XRD and XPS). The poor catalytic performance of (VO)₂P₂O₇ is mainly due to strong product adsorption which is favoured by surface OH-groups formed under reaction conditions. This process can be partially suppressed by adding competitive adsorbates to the feed. In K-V₂O₅ catalysts, a potassium vanadate phase is formed on the surface in which about 25% of the vanadium ions are tetravalent. This leads to lower acidity and oxidation potential of the surface and, thus, to improved benzaldehyde selectivities.     

Innovative Catalysts for Oxidative Dehydrogenation in the Gas Phase – Metallic Short Fibers and Coated Glass Fabrics

The catalytic activity of metallic short fibers with chosen alloy components and textures was investigated in the oxidative dehydrogenation (ODH) of propane to yield propene, and of isopropanol to yield acetone. The short fibers were synthesized using a melt extraction process and the properties of the fibers were intensely characterized. A correlation between the structure and the catalytic activity of the material was established. Optical microscopic, DSC, XRD, REM and EDX methods were used to characterize the fibers. Selective results of the dependency of the temperature on the propane conversion are presented in this work. A yield of more than 35 % propene is obtained at a propane conversion of 50 %. The ODH of isopropanol to acetone occurred with attractive yields of over 80 %. The results demonstrate the high innovative potential of the metal fiber materials. The use of coated glass fabrics as catalysts for the ODH and total oxidation of propane were also part of this investigation.     

Functional requirements for component films in a solar thin-film photovoltaic/thermal panel

The functional requirements of the component films of a solar thin-film photovoltaic/thermal panel were considered. Particular emphasis was placed on the new functions, that each layer is required to perform, in addition to their pre-existing functions. The cut-off wavelength of the window layer, required for solar selectivity, can be achieved with charge carrier concentrations typical of photovoltaic devices, and thus does not compromise electrical efficiency. The upper (semiconductor) absorber layer has a sufficiently high thermal conductivity that there is negligible temperature difference across the film, and thus negligible loss in thermal performance. The lower (cermet) absorber layer can be fabricated with a high ceramic content, to maintain high solar selectivity, without significant increase in electrical resistance. A thin layer of molybdenum-based cermet at the top of this layer can provide an Ohmic contact to the upper absorber layer. A layer of aluminium nitride between the metal substrate and the back metal contact can provide electrical isolation to avoid short-circuiting of series-connected cells, while maintaining a thermal path to the metal substrate and heat extraction systems. Potential problems of differential contraction of heated films and substrates were identified, with a recommendation that fabrication processes, which avoid heating, are preferable.     

Electrochemical fabrication of a heterogeneous binary SAM on polycrystalline Au

An electrochemical method for generating a phase-segregated mixed monolayer of 2-aminoethanethiol (AET) and 11-mercaptoundecanoic acid (MUA) on a polycrystalline gold bead electrode is presented. Electric potential was used to disrupt a monolayer of AET on Au through numerous cycles of reductive desorption followed by incomplete readsorption. Cyclic voltammetry and differential capacitance were used to monitor the successive removal of AET from the metal with potential cycling; however, capacitance was determined to be a more sensitive measure of fractional coverage. Using differential capacitance as a probe, we determined the most efficient method to make the Au surface completely void of AET involved a potential step to a significantly negative potential for a holding time of 15 min. Using this optimal condition, the negative potential was restricted to limit desorption of AET from only the (1 1 1) sites of the polycrystalline metal. The exposed Au(1 1 1) regions were backfilled with MUA through a separate incubation resulting in the formation of the heterogeneous mixed monolayer with limited thiol exchange of the residual AET for the incoming MUA.     

Design of interference fits via finite element method

Studies of interference fits in ring gear-wheel connections show that the traditional design method based on thick-wall cylinder theory has some limitations. Application of the finite element method (FEM) for the three-dimensional stress analysis of interference fitted connections gives more complete and accurate results than the traditional method. An improved design method utilizes two safety factors, λ_s and λ_p, providing a new approach for evaluating the quality of interference fits. A tolerancing method utilizing the I_max and I_min curves provides a quantitative guideline for interference fit design. The selective assembly method combined with the FEM-based method for interference fit design provides an effective approach to achieve more reliable interference-fitted connections and more precise assembly with lower manufacturing cost.     

油基细水泥水化机理研究

采用热重分析（TG）、差热分析（DSC）、X衍射（XRD）、扫描电镜（SEM）和压汞（MIP）等方法研究了选择性堵水材料--油基水泥的水化机理，并借助烧失法测定水泥石化学结合水含量，使用甘油法测量Ca(OH)₂含量并分析了油基水泥水化程度。结果表明：油基水泥的初期水化速度快，Ca(OH)₂迅速生成，并形成CSH等大量水化产物，硬化油基水泥石抗压强度主要受水灰比的影响，在水灰比为0.26处达到最高抗压强度，并在较宽的水灰比范围内良好固化，是一种优良的选择性堵水材料。相比水基水泥石，硬化油基水泥石体系孔隙度更大，这是硬化油基水泥抗压强度不高的主要原因。