基于SIP的嵌入式VOIP终端研究与实现

近年来,多媒体通信技术发展迅速,SIP协议得到了广泛应用。IP电话自问世以来,由于其低廉的通话费用,高智能化及较高的通话质量等特点,受到了人们的广泛关注,给传统通话技术带来了严峻挑战。主要对嵌入式linux平台下VOIP终端的实现进行了研究,着重讨论了嵌入式PJSIP协议栈的移植、软终端的实现,以及图形用户界面(GUI)的设计。     

On-board control in the RoboCup small robots league

We present the most recent version of our RoboCube system, a special robot controller hand-tailored for players in the small robots league. The RoboCube is conceptualized to implement players with as many on-board features as possible in an extremely flexible way. For this purpose, the RoboCube provides significant computation power and memory as well as a multitude of I/O interfaces within the space constraints. As it facilitates the use of many sensors and effectors, including their on-board processing, the RoboCube allows us to explore a large number of different robots and team set-ups.     

Fabrication of embedded fine line inductors by constrained sintering and formulation of photoimageable conductive paste

Abstract

For miniaturisation and precision of electronic device, the new technologies such as photoimageable thick film process were combined with conventional thick film process, and constrained sintering with near zero shrinkage in the x and y direction has been proposed. In this research, photoimageable conductive paste for forming embedded components via constrained sintering by low temperature cofired ceramic (LTCC) technology was formulated. Afterwards, by optimising paste formulation, formation process of fine line and sintering method, miniaturised LTCC components especially embedded fine line inductors were fabricated and their properties such as line resolution, surface morphology and yield were investigated. As a result, embedded fine line inductors formed by constrained sintering with fine line resolution of 20 μm and yield over 90% were acquired.     

Closed-loop form quantization algorithm with bounded accumulative error

This paper proposes a closed-loop form quantization algorithm that guarantees the boundness of accumulative error. The algorithm is particularly useful for mobile robot navigation that is usually implemented on embedded systems. If the wheel command of the mobile robot is given by velocity or positional increments at every control instant that are quantized due to the finite word length of the controller's CPU, the quantization error accumulates to produce large position error. Such an error is critical for wheeled mobile robots or autonomous vehicles with non-holonomic constraints. To solve this problem, a non-error accumulative quantization algorithm with a closedloop form is presented. We can extend it to a generalized form corresponding to the nth-order accumulation. The boundness of the accumulative quantization error is proven via mathematic processes and verified by a series of computer simulations. The proposed method is effective to accurately control the autonomous mobile robot, particularly with embedded systems.     

Molecular dynamics study of a nano-particle joint for potential lead-free anisotropic conductive adhesives applications

Molecular dynamics (MD) simulation was performed to simulate the application of an anisotropic conductive adhesive (ACA). The dynamics of a copper sphere (radius 2 nm) between two copper substrates was investigated, using the embedded atom method (EAM). The structure evolution of the sphere was analyzed by x–z plane projection, pair-correlation function, and potential energy curve. x–z plane projection and potential energy curve showed that with applied strain the copper sphere went through an order–disorder–order type of phase transition. Pair-correlation function results showed a more ordered sphere structure with applied compressive strain as compared to the simulation without strain.     

Adhesion Characteristics of Carbon Black Embedded Glass/Epoxy Composite

The surface of glass/epoxy composite material was embedded with carbon black which was dispersed in methyl ethyl ketone (MEK) during the curing process to enhance the adhesion strength of the glass/epoxy composite structure. The morphological effect of the carbon black on the surface of composite was observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Quantitative chemical bonding analysis with X-ray photoelectron spectroscopy (XPS) was also performed to observe chemical bonding states on the surface. The lap shear strength of the glass/epoxy composite adhesive joints where composite adherends were embedded with carbon black was investigated with respect to the type and amount of embedment. Also, the tensile properties of the carbon black embedded glass/epoxy composites were measured to observe the mechanical degradation of the composite due to the MEK. The surface free energies of carbon black embedded composites were determined from the van Oss–Chaudhury–Good equation to correlate the lap shear strength of the adhesive joints with the surface free energies of composite adherends. From the experimental results, it was found that the carbon black embedment of the composite adherend improved much the bond strength due to the increased surface roughness on nano-scale as well as increased surface free energy.     

Procedure Based Program Compression

Cost and power consumption are two of the most important design factors for many embedded systems, particularly consumer devices. Products such as Personal Digital Assistants, pagers with integrated data services, and smart phones have fixed performance requirements but unlimited appetites for reduced cost and increased battery life. Program compression is one technique that can be used to attack both of these problems. Compressed programs require less memory, thus reducing the cost of both direct materials and manufacturing. Furthermore, by relying on compressed memory, the total number of memory references is reduced. This reduction saves power by lowering the traffic on high capacitance buses. This paper will discuss a new approach to implementing transparent program compression that requires little or no hardware support. Procedures are compressed individually, and a directory structure is used to bind them together at runtime. Decompressed procedures are explicitly cached in ordinary RAM as complete units, thus resolving references within each procedure. This approach has been evaluated on a set of 25 embedded multimedia and communications applications, and results in an average memory reduction of 40% with a runtime performance overhead of 10%.