Algorithm for cavity flow in a new-born goaf and experimental verification

Prevention and control measures of spontaneous combustion of coal and gas accumulation in a goaf require an accurate description of its gas flow state.However,the commonly used fluid dynamics in porous media is not suitable for the new-born goaf with fracture cavity combination,multi-scale,and large blocks.In this study,we propose a cavity flow algorithm to accurately describe the gas flow state in the new-born goaf.The genetic algorithm(GA)is used to randomly generate the binary matrix of a goaf caving shape.The difference between the gas flow state calculated by the lattice Boltzmann method(LBM)and the measured data at the boundary or internal measuring points of the real goaf is taken as the GA fitness value,and the real goaf caving shape and the gas flow state are quickly addressed by GA.The experimental model of new-born goaf is established,and the laser Doppler anemometry(LDA)experiment is carried out.The results show that the Jaccard similarity coefficient between the reconstructed caving shape and the real caving shape is 0.7473,the mean square error between the calculated wind speed and the LDA-measured value is 0.0244,and the R2 coefficient is 0.8986,which verify the feasibility of the algorithm.

Host Re-identification of Cyanophage PP and Its Implications for Host Range and Specificity

Dear Editor,In this study,we re-identified the hosts of cyanophage PP.Twenty-three candidate algal strains were tested,and the results indicated that seven strains belonging to Plectonema and Phormidium are the hosts of cyanophage PP,including two previously reported filamentous cyanobacteria,Plectonema boryanum and Phormidium

Total nitrogen and community turnover determine phosphorus use efficiency of phytoplankton along nutrient gradients in plateau lakes

Numerous studies support that biodiversity predict most to ecosystem functioning,but whether other factors display a more significant direct impact on ecosystem functioning than biodiversity remains to be studied.We investigated 398 samples of the phytoplankton phosphorus resource use efficiency(RUE_(P)=chlorophyll-a concentration/dissolved phosphate)across two seasons in nine plateau lakes in Yunnan Province,China.We identified the main contributors to phytoplankton RUEP and analyzed their potential influences on RUEP at different lake trophic states.The results showed that total nitrogen(TN)contributed the most to RUEP among the nine lakes,whereas community turnover(measured as community dissimilarity)explained the most to RUEP variation across the two seasons.Moreover,TN also influenced RUEP by affecting biodiversity.Species richness(SR),functional attribute diversity(FAD2),and dendrogram-based functional diversity(FDc)were positively correlated with RUEP in both seasons,while evenness was negatively correlated with RUEP at the end of the rainy season.We also found that the effects of biodiversity and turnover on RUEP depended on the lake trophic states.SR and FAD2 were positively correlated with RUEP in all three trophic states.Evenness showed a negative correlation with RUEP at the eutrophic and oligotrophic levels,but a positive correlation at themesotrophic level.Turnover had a negative influence on RUEP at the eutrophic level,but a positive influence at the mesotrophic and oligotrophic levels.Overall,our results suggested that multiple factors and nutrient states need to be considered when the ecosystem functioning predictors and the biodiversityecosystem functioning relationships are investigated.

Improved Pigeon-Inspired Optimization in an Integrated Obstacle Avoidance Method for Mars UAV Formation

This paper models the Mars UAV formation exploring the surface of Mars,and then the formation obstacle avoidance is brought up with the assumptions of the Mars circumstance and the UAVs.Based on their specialty,constrained Delaunay triangulation,Yen-K shortest path algorithm,the collaborative function,and the improved pigeon-inspired optimization(PIO)algorithm are integrated to solve the obstacle avoidance for the formation.Since the steering maneuver costs much energy and increases instabilities vulnerable in extraterrestrial exploration,the paper focuses on the route smoothness problem.The PIO is improved to be suitable for smooth routes and is compatible with other PIO variants.The simulation results show that the sum of the steering angle,namely the performance index,is e®ectively reduced and satises the obstacle avoidance requirements for Mars UAV formation.

Seasonal and spatial distributions of euphotic zone and longterm variations in water transparency in a clear oligotrophic Lake Fuxian, China

To assess the seasonal and spatial variations and long-term trends in water optical properties in Lake Fuxian, investigations based on field work in four seasons and a long-term analysis of data from 1980 to 2014 were conducted. The results show that there was no significant variation in the euphotic depth（Z（eu）） across the four seasons, and no significant correlations between Z（eu） and potential influencing factors in seasons other than summer, suggesting that the water itself may be a major factor regulating the Z（eu）in general. Nevertheless, significant differences in Z（eu） between the north region（NR） and the south region（SR） were observed in all seasonal tests except spring. This finding relates to a higher abundance of chromophoric dissolved organic matter（CDOM） in the NR due to runoff, especially in the rainy seasons（summer and autumn）.CDOM and its terrigenous component had an important impact on Z（eu）in summer, with the highest precipitation, and impacts from suspended solids and non-algal particles were also found in the NR in summer. The Secchi disk depth in the lake decreased clearly over the years,with significantly negative correlations with the increasing permanganate index and air temperature, implying that organic contaminants（CDOM and/or phytoplankton） are important regulators of water transparency. We estimate that the combined effects of climate warming and changes in land use and land cover are also indirect regulating factors. These findings should be considered in the protection of Lake Fuxian, owing to the importance of light penetration in aquatic ecosystems.

Influence of sunlight on the proliferation of cyanobacterial blooms and its potential applications in Lake Taihu, China

To learn the relationship between sunlight intensity and cyanobacterial proliferations for the further control of the heavy blooms, enclosure experiment were conducted in Meiliang Bay, Lake Taihu by regulating the natural light intensities with different shading ratio （0% （full sunlight）, 10%, 25%, 50% and 75% of original natural sunlight intensities） from September to November in 2010. The results indicated that phytoplankton biomass （mean） decreased significantly when the shading ratios reached 50% or more. Higher shading ratios （e.g. 75%） were very efficient in controlling the average and total cyanobacterialbloom biomass, while 50% shading ratio was proven very effective either in controlling the peak value of phytoplankton biomass or postponing the occurrence of cyanobacterial blooms in Lake Talhu. In addition, phytoplankton composition and photosynthesis efficiency were also affected by altering the shading ratios, and in turn, they might also act on phytoplankton growth. Based on the results from the present study, intermediate shading strategies such as regulation of water level or turbidity through the hydrology regulations would probably be an effective and efficient method in controlling cyanobacterial blooms in large and shallow lakes.

Simultaneous elimination of cyanotoxins and PCBs via mechanical collection of cyanobacterial blooms:An application of“green-bioadsorption concept”

In this study,the distribution,transfer and fate of both polychlorinated biphenyls（PCBs）and cyanotoxins via phytoplankton routes were systematically investigated in two Chinese lakes.Results indicated that PCB adsorption/bioaccumulation dynamics has significantly positive correlations with the biomass of green alga and diatoms.Total lipid content of phytoplankton is the major factor that influences PCB adsorption/bioaccumulation.Cyanobacterial blooms with relatively lower lipid content could also absorb high amount of PCBs due to their high cell density in the water columns,and this process was proposed as major route for the transfer of PCBs in Chinese eutrophic freshwater.According to these findings,a novel route on fates of PCBs via phytoplankton and a green bioadsorption concept were proposed and confirmed.In the practice of mechanical collections of bloom biomass from Lake Taihu,cyanotoxin/cyanobacteria and PCBs were found to be removed simultaneously very efficiently followed this theory.