Implementation of VxWorks in autopilot for micro aerial vehicle based on PXA255 and FPGA

The overall hardware construction of autopilot within micro aerial vehicle is presented. The boot process of VxWorks real time operating system as well as the conception and function of board support package （BSP） is described. And the transplantation process of the VxWroks operat ing system into the hardware platform mentioned above is highlighted. It is shown from the final re sults that VxWorks has high stability and real time performance, ensuring accurate flight control and a smooth flight of the micro aerial vehicle.

Experimental Evaluation of TCP and ICMP in Network Measurement

Network measurement is an important approach to understand network behaviors, which has been widely studied. Both Transfer Control Protocol （TCP） and Interact Control Messages Protocol （ICMP） are applied in network measurement, while investigating the differences between the measured results of these two protocols is an important topic that has been less investigated. In this paper, to compare the differences between TCP and ICMP when they are used in measuring host connectivity, RTT, and packet loss rate, two groups of comparison programs have been designed, and after careful evaluation of the program parameters, a lot of comparison experiments are executed on the Internet. The experimental results show that, there are significant differences between the host connectivity measured using TCP or ICMP; in general, the accuracy of connectivity measured using TCP is 20%- 30% higher than that measured using ICMP. The case of RTT and packet loss rate is complicated, which are related to path loads and destination host loads. While commonly, the RTF and packet loss rate＂ measured using TCP or ICMP are very close. According to the experimental results, some advices are also given on protocol selection for conducting accurate connectivity, RTF and packet loss rate measurements.

Virtual resource monitoring in cloud computing

Cloud computing is a new computing model. The resource monitoring tools are immature compared to traditional distributed computing and grid computing. In order to better monitor the virtual resource in cloud computing, a periodically and event-driven push （PEP） monitoring model is proposed. Taking advantage of the push and event-driven mechanism, the model can provide comparatively adequate information about usage and status of the resources. It can simplify the communication between Master and Work Nodes without missing the important issues happened during the push interval. Besides, we develop ＂mon＂ to make up for the deficiency of Libvirt in monitoring of virtual CPU and memory.

Tree-based backoff protocol for fast RFID tag identification

This paper proposes a tree-based backoff （TBB） protocol that reduces the number of iterations implemented in the procedure of tag collision arbitration in radio frequency identification （RFID） systems. This is achieved by employing the following mechanisms： one is send the request command iteratively to all tags in the interrogation zone until a single tag is identified. The other is backward to the parent node instead of root node to obtain the request parameters and send the request command again until all tags are identified. Compared with the traditional tree-based protocol, on average, simulated results show that the TBB protocol reduces the number of the iterations by 72.3% and the identification delay by 58.6% and achieves the goal of fast tag identification.

Editing Algorithms for Non-Linear Editing Systems Based on MPEG-2

MPEG-1/2-based non-linear editing systems appear to have a tendency to replace the M-JPEG systems, but in so doing it is difficult to realize the video, audio and the synchronization editing algorithms. Such editing algorithms are presented. Based on an analysis of the structure of the MPEG-1/2 stream, and using parameters of the video, audio and the synchronization information, the video, audio and synchronization editing algorithms are provided. The characters of the algorithms are efficient, the quality loss of frames is low because it only decodes and codes part of the data; the editing algorithm is fast through use of some index files; synchronization editing is realized using the synchronization information, such as PTS, ESCR and other parameters.

A TOOL PATH CORRECTION AND COMPRESSION ALGORITHM FOR FIVE-AXIS CNC MACHINING

A novel approach is proposed for correcting command points and compressing discrete axis commands into a C2 continuous curve.The relationship between values of rotation angles and tool posture errors is firstly analyzed.A segmentation method based on values of rotation angles and lengths of adjacent points is then used to subdivide these command points into accuracy regions and smoothness regions.Since tool center points generated by CAD/CAM system are usually lying in the space that is apart from the desired curve within a tolerance distance,and the corresponding tool orientation vector may change a lot while the trajectory length of the tool center point is quite small,directly machining with such points will lead to problems of coarse working shape and long machining time.A correction method for command points is implemented so that good processing effectiveness can be achieved.Also,the quintic spline is used for compressing discrete command points into a C2 continuous smooth curve.The machining experiment is finally conducted to demonstrate the effectiveness of the proposed algorithm.