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Multipoint communication has been an increasingly focused topic in computer communication networks, including both the Internet and the ATM networks. We have previously presented, analyzed, and evaluated new point-tomultipoint ABR flow control algorithms. In this paper, we focus on multipoint-to-point flow control. As the major objective of ABR service is to provide minimum-loss, fair service to data traffic, an effective merge-point scheme for multipoint-to-point flow control should guarantee some suitable fairness. In this paper, we first examine the "essential fairness" concept proposed by Wang and Schwartz for point-to-multipoint flow control in the Internet. We extend and enhance the concept to the multipoint-to-point ABR flow control. A general algorithm guaranteeing essential fairness is presented, with a detailed implementation on top of the ERICA unicast algorithm proposed by Jam, et. al. The general algorithm may be used for a wide range of fairness specifications to accommodate various bandwidth requirement from unicast or multicast sources of different application streams.Three major variations of the general algorithm are presented. These three schemes are simulated and evaluated, and compared with an existing scheme proposed by Ren, Siu, and Suzuki. Simulation results show that the proposed merge-point algorithm achieves, within short transient time, max-mm fairness based on different weights given to individual sources or sessions, or according to various specifications of fairness. The fairness concept and the general algorithm presented here may be readily applied to other high-speed networks such as the Next Generation Internet and Wireless ATM, and to different multicast settings such as point-to-multipoint and multipoint-to-multipoint.

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This paper researches on the levitation and drag forces of Halbach permanent-magnet electrodynamic suspension. First, construct an analytical model to calculate the magnetic field in the air gap and the current in the secondary conductor plate, thus deducing analytical expressions of the levitation and drag forces. Second, establish a 2D and a 3D finite element model, using ANSYS. Finally, at different speeds, from 0 to 250 km/h, compare the forces calculating results through the above three methods. Results generating from the 2D-FEM and the analytical algorithm have less than 3% of relative error, but for having not taken the horizontal components of eddy current in the reaction plate into consideration, thus 10% more than the 3D-FEM calculating results.

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