碳纳米管(CNT)场发射显示器的关键技术的研究

对碳纳米管阴极的制备以及场发射显示器的真空封装技术进行了研究.利用一种新的碳纳米管生长工艺制备出了具有优良场发射性能的碳纳米管阴极.并将这种直接生长的碳纳米管薄膜作为阴极,结合一种弹性封装工艺,开发了一种具有简单字符显示功能的场发射显示器.该显示器在较低的工作电压下就可获得高亮度的显示效果,并且器件的亮度与驱动电压成较好的线性关系,这将有利于未来的碳纳米管场发射显示器实现高亮度和多级灰度显示.器件的持续工作寿命测试已经超过5500小时,充分验证了碳纳米管作为场发射阴极的应用潜力.     

3D polymeric microfluidic device fabrication via contact liquid photolithographic polymerization (CLiPP)

In this contribution, a new method for the fabrication of complex polymeric microfluidic devices is presented. The technology, contact liquid photolithographic polymerization (CLiPP), overcomes many of the drawbacks associated with other rapid prototyping schemes, such as limited materials choices and time-consuming microassembly protocols. CLiPP shares many traits with other photolithographic methods, but three distinct features: (i) liquid photoresists in contact with the photomask, (ii) readily removed sacrificial materials, and (iii) living radical processes, enable multiple polymeric chemistries and mechanical properties while simultaneously enabling facile fabrication of 3D geometries and surface chemistry control. This contribution details fabrication techniques and methods for the fabrication of high aspect ratio posts covalently bonded to a polymeric substrate, an array of independently stacked bars on top of perpendicular bars, multiple undercut structures fabricated simultaneously, and a complex 3D geometry with intertwined channels.     

Goal-directed imitation for robots: A bio-inspired approach to action understanding and skill learning

In this paper we present a robot control architecture for learning by imitation which takes inspiration from recent discoveries in action observation/execution experiments with humans and other primates. The architecture implements two basic processing principles: (1) imitation is primarily directed toward reproducing the outcome of an observed action sequence rather than reproducing the exact action means, and (2) the required capacity to understand the motor intention of another agent is based on motor simulation. The control architecture is validated in a robot system imitating in a goal-directed manner a grasping and placing sequence displayed by a human model. During imitation, skill transfer occurs by learning and representing appropriate goal-directed sequences of motor primitives. The robustness of the goal-directed organization of the controller is tested in the presence of incomplete visual information and changes in environmental constraints.     

Design space exploration of reliable networked embedded systems

In this paper, a new methodology is presented for topology optimization of networked embedded systems as they occur in automotive and avionic systems as well as wireless sensor networks. By introducing a model which is (1) suitable for heterogeneous networks with different communication bandwidths, (2) modeling of routing restrictions, and (3) flexible binding of tasks onto processors, current design issues of networked embedded systems can be investigated. On the basis of this model, the presented methodology firstly allocates the required resources which can be communication links as well as computational nodes and secondly binds the functionality onto the nodes and the data dependencies onto the links such that no routing restrictions will be violated or capacities on communication links will be exceeded. Due to the often error-prone communication in networks, we allow for routing each data dependency over multiple routes in the networks. With this strategy, our methodology is able to increase the reliability of the entire system. This reliability analysis is based on Binary Decision Diagrams (BDDs) and is integrated in our multi-objective design space exploration. By applying Evolutionary Algorithms, we are able to consider multiple objectives simultaneously during the optimization process and allow for a subsequent unbiased decision making. An experimental evaluation as well as a demonstration of a case study from the field of automotive electronics will show the applicability of the presented approach.     

Amorphous chromium silicide formation in hydrogenated amorphous silicon

The interaction between thin films of hydrogenated amorphous silicon and sputter-deposited chromium has been studied. Following deposition of the chromium films at room temperature, the films were annealed over a range of times and temperatures below 350°C. It was found that an amorphous silicide was formed only a few nanometers thick with the square of thickness proportional to the annealing time. The activation energy for the process was 0.55±0.05 eV. The formation process of the silicide was very reproducible with the value of density derived from the thickness and Cr surface density being close to the value for crystalline CrSi₂ for all films formed at temperatures ≤300°C. The specific resistivity of the amorphous CrSi₂ was ≈600 μΩ·cm and independent of annealing temperature.     

Further improvement in high crystalline quality of homoepitaxial CVD diamond

High-quality homoepitaxial diamond (001) films with macroscopically flat surfaces have been successfully grown using a high-power microwave-plasma chemical-vapor-deposition (MWPCVD) method. In this study, further optimization of the homoepitaxial growth condition has been accomplished mainly by controlling off-angles to 5° along the <110> or <100> direction of high-pressure/high-temperature-synthesized Ib diamond (001) substrates. We have found that the homoepitaxial films deposited at reasonably high growth rates under the optimized growth condition including the off-angle of 3°–4° along the <110> direction have macroscopically flat surfaces, accompany very low or almost negligible densities of growth hillocks and yield strong free-exciton emissions in both steady-state cathodoluminescence and time-resolved photoluminescence spectra measured at room temperature. These indicate that apparent lateral growths suitable for high-quality homoepitaxial layers in the case of the high-power MWPCVD method, which are similar to those previously reported in the case of MWPCVD processes with low methane concentrations, rather quickly occur from step edges on (001) terraces and that they can be achieved more preferentially on the vicinal substrates at high temperatures and high methane concentrations.     

Improved Repeatability of Pulsed Field Magnetometry Measurements Through Peltier Effect Temperature Control of Measurement Coils

Pulsed Field Magnetometers (PFMs) offer a method for high speed full loop characterisation of hard magnetic materials. As there is no dependency on iron to close a circuit, the repeatability of the technique is good. By utilising Peltier effect techniques to control the temperature of the measurement coil systems employed in a Pulsed Field Magnetometer, the level of repeatability of measurements can be significantly improved.     

Performance of miniaturized direct methanol fuel cell (DMFC) devices using micropump for fuel delivery

A fuel cell is a device that can convert chemical energy into electricity directly. Among various types of fuel cells, both polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) can work at low temperature (<80 °C). Therefore, they can be used to supply power for commercial portable electronics such as laptop computers, digital cameras, PDAs and cell phones. The focus of this paper is to investigate the performance of a miniaturized DMFC device using a micropump to deliver fuel. The core of this micropump is a piezoelectric ring-type bending actuator and the associated nozzle/diffuser for directing fuel flow. Based on the experimental measurements, it is found that the performance of the fuel cell can be significantly improved if enough fuel flow is induced by the micropump at anode. Three factors may contribute to the performance enhancement including replenishment of methanol, decrease of diffusion resistance and removal of carbon dioxide. In comparison with conventional mini pumps, the size of the piezoelectric micropump is much smaller and the energy consumption is much lower. Thus, it is very viable and effective to use a piezoelectric valveless micropump for fuel delivery in miniaturized DMFC power systems.     

An efficient face segmentation algorithm based on binary partition tree

This paper presents an efficient face segmentation algorithm based on binary partition tree. Skin-like regions are first obtained by integrating the results of pixel classification and watershed segmentation. Facial features are extracted by the techniques of valley detection and entropic thresholding, and are used to refine the skin-like regions. In order to segment the facial regions from the skin-like regions, a novel region merging algorithm is proposed by considering the impact of the common border ratio between adjacent regions, and the binary partition tree is used to represent the whole region merging process. Then the facial likeness of each node in the binary partition tree is evaluated using a set of fuzzy membership functions devised for a number of facial primitives of geometrical, elliptical and facial features. Finally, an efficient algorithm of node selecting in the binary partition tree is proposed for the final face segmentation, which can exactly segment the faces without any underlying assumption. The performance of the proposed face segmentation algorithm is demonstrated by experimental results carried out on a variety of images in different scenarios.