Dynamic routing and wavelength assignment algorithm of optical satellite networks based on cross-layer design

In order to overcome the adverse effects of Doppler wavelength shift on data transmission in the optical satellite networks,a dynamic routing and wavelength assignment algorithm based on crosslayer design( CL-DRWA) is introduced which can improve robustness of the network. Above all,a cross-layer optimization model is designed,which considers transmission delay and wavelength-continuity constraint,as well as Doppler wavelength shift. Then CL-DRWA is applied to solve this model,resulting in finding an optimal light path satisfying the above constraints for every connection request. In CL-DRWA,Bellman-Ford method is used to find an optimal route and a distributed relative capacity loss method is implemented to get an optimal wavelength assignment result on the optimal route. Moreover,compared with the dynamic routing and wavelength assignment algorithm based on minimum delay strategy( MD-DRWA),CL-DRWA can make an improvement of 5. 3% on the communication success probability. Meanwhile,CL-DRWA can meet the requirement of transmission delay for real-time services.

Nutrient depletion is the main limiting factor in the crude oil bioaugmentation process

The biodegradation was considered as the prime mechanism of crude oil degradation.To validate the efficacy and survival of the crude oil-degrading strain in a bioremediation process,the enhanced green fluorescent protein gene(egfp)was introduced into Acinetobacter sp.HC8-3 S.In this study,an oil-contaminated sediment microcosm was conducted to investigate the temporal dynamics of the physicochemical characterization and microbial community in response to bacterium amendment.The introduced strains were able to survive,flourish and degrade crude oil quickly in the early stage of the bioremediation.However,the high abundance cannot be maintained due to the ammonium(NH 4^(+)-N)and phosphorus(PO 4^3--P)contents decreased rapidly after 15 days of remediation.The sediment microbial community changed considerably and reached relatively stable after nutrient depletion.Therefore,the addition of crude oil and degrading cells did not show a long-time impact on the original microbial communities,and sufficient nitrogen and phosphorus nutrients ensures the survive and activity of degrader.Our studies expand the understanding of the crude oil degradative processes,which will help to develop more rational bioremediation strategies.