一种基于对称集的平面图形匹配新方法

定义了一种新的形状描述子和一种矩阵内积.该描述子是二值对角对称图表,此图表具有图形上成对点的全局对称特性.在定义了矩阵的内积基础上,计算了两图形的匹配值.此定义方法缩短了匹配值的计算时间,通过几种类别的图形测试了这种描述子的描述能力.     

曲面造型的几何体素构造法

在ＣＡＤ，ＣＡＭ系统中，怎样更好地构造出有效的物体几何模型是系统的关键问题．现代几何造型技术的引入使其迎刃而解．本文通过对几何造型技术的研究，采用几何体素构造法对某些复合曲面进行了构造，并运用所开发的ＧＭＳ曲面造型系统进行了锻模型腔中圆弧、圆环过渡面的造型设计．     

新型单槽磷酸反应器（RTCB）的开发研究

本文旨在开发一种新型磷酸反应器──具有类似太极图曲线形隔板的单槽双区四桨反应器（ＲＴＣＢ反应器）。首先以自来水和磷石膏为搅拌介质进行冷模实验，冷模实验结果表明，ＲＴＣＢ反应器具有功耗低、悬浮、混合效果好、停留时间分布合理等优点。然后，采用同样的二水物流程工艺条件，选取道尔槽作参照物进行热模实验，热模实验结果表明，相同条件下与道尔槽相比，ＲＴＣＢ槽具有省功、磷石膏结晶环境优越、磷石膏洗涤率稍高等优点，但磷矿萃取率稍低，可望用于湿法磷酸的工业化生产。本文的研究工作将为该反应器的进一步开发应用提供依据。     

卧式下肢康复机器人主动柔顺控制实验研究

为保证下肢运动功能障碍患者在康复训练中的安全性和舒适性,利用力反馈信息采用阻抗控制原理设计了康复机器人系统的控制器,通过调整末端位置与力之间的关系使机器人具有一定的柔顺性.建立了系统的控制模型,并在dSPACE平台上进行了实验研究.结果表明,通过调节控制器中的阻抗参数,可以使机器人获得不同的刚度特性和阻尼特性,同时分析...     

The theory of multiple peeling

In this paper we derive the theory of multiple peeling, extending the pioneering energy-based single peeling theory of Kendall, including large deformations and pre-stretching. We can thus treat a complex system of films, adhering over a substrate and having a common hinge where the pulling force is applied. Two case studies are investigated: the asymmetric V-shape double peeling and the symmetric cone-shape configuration with N peeling tapes, both requiring the solution of six nonlinear coupled equations (instead of the one needed in the simpler single peeling problem). Remarkable implications emerge: (1) for moderate deformations, the critical strain of a tape is identical to that of the single peeling; (2) an optimal peeling angle, at which adhesion is maximal, is discovered; (3) an additional optimization, even for hierarchical structures, is introduced by imposing the delamination force equal to the intrinsic fracture of the tape. Also, the length of the peeling process zone is calculated, suggesting different optimal values for flaw-tolerant peeling at different angles. Applications to gecko adhesion, for which the flaw-tolerant peeling is demonstrated, and spider silk anchors, that we are going to discuss in details in subsequent papers, are envisioned (including a new pre-stretching mechanism for adhesion control) and suggested by the evidence of a smart mechanism capable of maximizing adhesion simply by increasing the applied tension.     

Multifunctional picoliter droplet manipulation platform and its application in single cell analysis

We developed an automated and multifunctional microfluidic platform based on DropLab to perform flexible generation and complex manipulations of picoliter-scale droplets. Multiple manipulations including precise droplet generation, sequential reagent merging, and multistep solid-phase extraction for picoliter-scale droplets could be achieved in the present platform. The system precision in generating picoliter-scale droplets was significantly improved by minimizing the thermo-induced fluctuation of flow rate. A novel droplet fusion technique based on the difference of droplet interfacial tensions was developed without the need of special microchannel networks or external devices. It enabled sequential addition of reagents to droplets on demand for multistep reactions. We also developed an effective picoliter-scale droplet splitting technique with magnetic actuation. The difficulty in phase separation of magnetic beads from picoliter-scale droplets due to the high interfacial tension was overcome using ferromagnetic particles to carry the magnetic beads to pass through the phase interface. With this technique, multistep solid-phase extraction was achieved among picoliter-scale droplets. The present platform had the ability to perform complex multistep manipulations to picoliter-scale droplets, which is particularly required for single cell analysis. Its utility and potentials in single cell analysis were preliminarily demonstrated in achieving high-efficiency single-cell encapsulation, enzyme activity assay at the single cell level, and especially, single cell DNA purification based on solid-phase extraction.     

Enhancement of gas sensing properties of CdS nanowire/ZnO nanosphere composite materials at room temperature by visible-light activation

CdS nanowire/ZnO nanosphere materials (CdS/ZnO) with hierarchical structure were synthesized by a three-step solvothermal process. XRD, FESEM and TEM analysis confirmed the growth of ZnO nanospheres on the surface of CdS nanowires (NWs). The transient photovoltage (TPV) measurements revealed that the interface between CdS and ZnO can inhibit the recombination of photogenerated excess carriers and prolong the lifetime of excess carriers in CdS/ZnO materials. Moreover, the CdS/ZnO materials exhibit a dramatic improvement in optoelectronic performance and visible-light-irradiation gas sensing activity, which gave 1 order of magnitude larger than that of CdS NWs in response to formaldehyde. The enhancement of sensing properties is attributed to the interfacial transport of excess carriers.     

Amazing ageing property and in situ comparative study of field emission from tungsten oxide nanowires

In this work, needle-shaping of tungsten oxide nanowires occurred during field emission characterization. Compared with nanowires with a flat apex, needle-shaped emitters showed a lower threshold field of 11.9 V μm(-1) for 1 mA cm(-2) and a higher emission current of 1120 μA at 16.2 V μm(-1). Most notably, the measured ageing current dramatically increased by more than four times until it slightly decreased, tending towards stability. In addition, the samples showed striking difference in their nonlinear Fowler-Nordheim plot before and after ageing tests. Selected area diffraction and transmission electron microscope characterizations were used to further study these amazing results.     

Fabrication of transparent polymer-matrix nanocomposites with enhanced mechanical properties from chemically modified ZrO<Subscript>2</Subscript> nanoparticles

Optically transparent nanocomposites with enhanced mechanical properties were fabricated using stable dispersions of sub 10 nm ZrO₂ nanoparticles. The ZrO₂ dispersions were mixed with a commercially available bisphenol-A-based epoxy resin (RIMR 135i) and cured with a mixture of two amine-based curing agents (RIMH 134 and RIMH 137) after complete solvent removal. The colloidal dispersions of ZrO₂ nanoparticles, synthesized through a non-aqueous approach, were obtained through a chemical modification of the ZrO₂ nanoparticle surface, employing different organic ligands through simple mixing at room temperature. Successful binding of the ligands to the surface was studied utilizing ATR–FT-IR and thermogravimetric analysis. The homogeneous distribution of the nanoparticles within the matrix was proven by SAXS and the observed high optical transmittance for ZrO₂ contents of up to 8 wt%. Nanocomposites with a ZrO₂ content of only 2 wt% showed a significant enhancement of the mechanical properties, e.g., an increase of the tensile strength and Young’s modulus by up to 11.9 and 12.5%, respectively. Also the effect of different surface bound ligands on the mechanical properties is discussed.     

Notch stress concepts for the fatigue assessment of welded joints - Background and applications

Among modern fatigue design concepts for welded structures, the linear-elastic notch stress concept gains increasing industrial acceptance. There are two variants of this concept, one for thick walled (t ? 5 mm) welded joints with the reference radius r_ref = 1.00 mm, which is already included in the fatigue design recommendations of the IIW and applied for the assessment of big welded structures, and one for thin walled (t < 5 mm) welded joints with the reference radius r_ref = 0.05 mm, which is more and more used in the automotive industry.The concept with r_ref = 1.00 mm is based on the micro-support theory of Neuber with the fictitious radius r_ref = 1.00 mm, derived by Radaj. The background of the concept with r_ref = 0.05 mm is the relationship between the stress-intensity factor and the notch stress according to Creager and Paris as well as Irvin’s theory of crack blunting. Besides these two theories, the definition of both of these radii has also an experimental background; they are observed in many welded joints.In the present paper, first the background and then different applications of both concept variants are described: the application of the reference radius of r_ref = 1.00 mm for MAG-welded offshore K-nodes (t = 30 mm) and sandwich panels for ship decks (t = 5 mm), and the application of r_ref = 0.05 mm for spot-welded automotive doors (t = 1 mm) and MAG-welded automotive trailing links (t = 3-4 mm). The sandwich panels were evaluated additionally with r_ref = 0.05 mm. Calculations and experimental results are compared and the reliability of the notch stress concept variants underlined. Additionally, recommendations for the slope of design lines distinguishing between thin and thick dimensions are given, i.e. k = 3.0 and 5.0 (normal stress, shear stress) for thick and stiff structures, k = 5.0 and 7.0 for thin and flexible structures.