Changes occurring in the friction and wear mechanisms during a load-carrying capacity test, lubricated with cetane containing a carboxylic acid, were investigated. The changes in wear scar/track appearance and oxide coverage/composition were analyzed during every load stage.The main conclusions were as follows:
The breakdown in the protective oxide layer formed on the opposing steel surfaces was found to be the prerequisite for initiation of seizure.
The seizure load achieved during load-carrying capacity testing quantifies the ability of the test fluid to prevent transition to the adhesive wear regime.
The most severe surface damage was found to occur during the first few seconds after test initiation. Desorption of the adsorbed lubricant film and the subsequent removal of the naturally occurring thin oxide layer results in the initial period of adhesive wear.
Partial recovery to a state of acceptable friction occurs after the period of initial seizure. During this period, the surface coverage by the adsorption lubricant molecules and the oxide coverage are sufficient to prevent severe adhesive wear from occurring. Wear is primarily a combination of oxidative, abrasive, and fatigue wear (all possible in the regions of mixed friction and boundary lubrication).
Final lubricant breakdown and eventual seizure are initiated when the oxide removal rate exceeds the oxide formation rate resulting in severe adhesive wear followed by seizure.
Mobile profile of WiMAX technology, based on IEEE 802.16e standard, is due to support multi-application services, while benefiting a wide range of implementation flexibilities. The current document presents a simple capacity estimation methodology for WiMAX systems. In this paper, the term capacity concerns with the maximum number of simultaneous multi-service users that each specific Mobile WiMAX access point can jointly support. A dynamic PHY+MAC overhead removal method is formulated to achieve an improved system goodput with respect to users distribution and multi-burst construction strategy. A service delivery model is presented that investigates the QoS requirements of the services to be supported, along with elaborating an application profile as a consistent input for capacitating and dimensioning studies. The minimum resource consumption calculation for the joint-application users is derived at each given time. An incremental algorithm compares the optimal available resources with minimum service demand for each number of users to arrive at maximum system capacity. Using the proposed algorithm, different simulation scenarios are studied based on the most used WiMAX implementation parameters in practice. The simulation results prove the significant roll of overhead calculation in performance evaluation studies. Furthermore, these results can be used for network planning and dimensioning purposes, as well as providing reference measures for scheduling performance analysis and detailed simulations. 相似文献
The CDMA/TDD system is a highly attractive solution to support the next generation cellular mobile systems which provide unbalanced multimedia services between downlink and uplink. In this paper, we analyze the interference for downlink and uplink timeslots in a multicell CDMA/TDD system. We also mathematically formulate an optimal timeslot and channel allocation problem considering capacity fairness among cells, which is to maximize the system capacity under the given traffic unbalance, and propose an efficient algorithm based on the simulated annealing technique. Extensive experimental results show that the proposed scheme yields a good performance, and fairness among cells improves with a decrease in the system capacity. 相似文献
