移动自组网协作策略研究与分析

针对移动自组网中自私节点拒绝转发数据包的服务请求,影响整体网络性能的问题进行研究,基于经济学中提出的博弈理论,描述了节点检测记录相邻节点的协作率而识别自私节点的方法,提出了主动能量制约策略AECS和基于统计信息的节点协作重复博弈策略LTFT,分析表明该策略和方法能够有效激励协作并孤立自私节点,能有效的解决网络性能与节点收益的权衡问题,在一定程度上解决节点的协作问题。     

Low-temperature properties of alkyl esters of tallow and grease

The low-temperature properties of mono-alkyl esters derived from tallow and recycled greases were determined for neat esters and 20% ester blends in No. 2 low-sulfur diesel fuel. Properties studied included cloud point, pour point, cold filter plugging point, low-temperature flow test, crystallization onset temperature, and kinematic viscosity. Compositional properties of the alkyl esters determined included water, residual free fatty acids, and free glycerol content. In general, the secondary alkyl esters of tallow showed significantly improved cold-temperature properties over the normal tallow alkyl ester derivatives. The low-temperature flow test did not show a 1:1 correlation with cloud point as previously observed with methyl soyate and methyl tallowate. For the homologous series methyl to n-butyl tallowate, ethyl tallowate had the best broad-spectrum low-temperature properties, both neat and when blended in diesel fuel. For the greases studied, both the normal and branched alkyl ester derivatives showed improved properties over corresponding tallow esters, especially with neat esters.     

A novel slurry bubble column membrane reactor concept for Fischer–Tropsch synthesis in GTL technology

Fischer–Tropsch synthesis (FTS) plays an important role in the production of ultra-clean transportation fuels, chemicals, and other hydrocarbon products. In this work, a novel combination of fixed-bed and slurry bubble column membrane reactor for Fischer–Tropsch synthesis has been proposed. In the first catalyst bed, the synthesis gas is partially converted to hydrocarbons in a water-cooled reactor which is fixed bed. In the second bed which is a membrane assisted slurry bubble column reactor, the heat of reaction is used to preheat the feed synthesis gas to the first reactor. Due to the decrease of H₂/CO to values far from optimum reactants ratio, the membrane concept is suggested to control hydrogen addition. A one-dimensional packed-bed model has been used for modeling of fixed-bed reactor. Also a one-dimensional model with plug flow pattern for gas phase and an axial dispersion pattern for liquid-solid suspension have been developed for modeling of slurry bubble column reactor. Proficiency of a membrane FTS reactor (MR) and a conventional FTS reactor (CR) at identical process conditions has been used as a basis for comparison in terms of temperature, gasoline yield, H₂ and CO conversion as well as selectivity. Results show a favorable temperature profile along the proposed concept, an enhancement in the gasoline yield and, thus a main decrease in undesirable product formation. The results suggest that utilizing this type of reactor could be feasible and beneficial. Experimental proof of concept is needed to establish the validity and safe operation of the proposed reactor.