Search

This paper proposes a new method to analyze Ethernet performance. Currently, most studies on Ethernet performance assume that the channel is divided into time slots, or the network load is saturated with little attention to a non-slotted channel and the non-saturation status. However, this situation is more consistent with the practical application of Ethernet. This paper first calculates the original collision probability and the retransmission collision probability in the original load, then obtains the retransmission load of the network based on those two collision probabilities, and finally acquires the actual load of the network by an iterative method. In addition, the accuracy of the analysis is checked against simulation results.

Noncircular bevel gear can achieve variable transmission between intersecting axes. This article proposes the design method of high-order noncircular bevel gear with concave pitch curve. The parametric equations for driving and driven gear, addendum and dedendum surface under given transmission ratio and axis angle are established in a spherical polar coordinate system. The tooth profile equation of noncircular bevel gear is derived according to the generation method by using bevel gear cutter. The three-dimensional model for noncircular bevel gear is developed to verify the correctness of the design method.

Preparation and characterization of blends and copolymers of a fluorinated polyimide with network constituents is reported. 4,4′‐Hexafluoroisopropylidene diphthalic anhydride and 4,4′‐diaminodiphenyl ether (6FDA–DDE) polyimide were used as the linear hosts and mellitic acid hexamethyl ester ‐ 4,4′‐diaminodiphenyl ether (MAHE–DDE) was employed as the network constituent for the blend and copolymer. Cast films of the polyimides were characterized by FTIR, XPS, DMA, and TGA. The multifunctional nature of MAHE facilitated crosslinking among the constituents. Both blends and copolymers showed significant improvement in the storage modulus and glass transition temperature relative to that observed for the 6FDA homopolymer. The occurrence of a single glass transition temperature for the blends suggests that they were at least partially miscible. Presence of low molecular weight species in the copolyimides, combined with steric hindrance to crosslinking, may have resulted in the existence of an optimum in the amount of the network components for improving the mechanical properties. Inclusion of network components is presented as a facile method for improving the desirable properties of polyimide. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3000–3008, 2006