To understand its source,distribution,storage,and translocation in the subtropical forest ecosystems,mercury(Hg)concentrations and stable isotopes in forest biomass tissues(foliage,branch,bark,and trunk)were investiga...To understand its source,distribution,storage,and translocation in the subtropical forest ecosystems,mercury(Hg)concentrations and stable isotopes in forest biomass tissues(foliage,branch,bark,and trunk)were investigated at Ailao Mountain National Nature Reserve,Southwest China.The total Hg(THg)concentrations in the samples show the following trend:mature foliage(57±19 ng g-1)>bark(11±4.0 ng g-1)>branch(5.4±2.5 ng g-1)>trunk(1.6±0.7 ng g-1).Using the measured THg concentrations and the quantity of respective biomasses,the Hg pools in the forest are:wood(60±26μg m-2)>bark(51±18μg m-2)>foliage(41±11μg m-2)>branch(26±8.3μg m-2).The tree biomasses displayed negativeδ202Hg(-1.83‰to-3.84‰)andΔ199Hg(-0.18‰to-0.62‰).The observedΔ200Hg(-0.08‰to 0.04‰)is not significantly from zero.AΔ199Hg/Δ201Hg ratio of 1.05 was found in tree biomasses,suggesting that mercury has undergone Hg(Ⅱ)photoreduction processes.A Hg-isotope based binary mixing model suggests that Hg in the tree biomasses mainly originated from foliage uptake of atmospheric Hg0,constituting 67%,80%,and 77%of Hg in wood,branch,and bark,respectively.Our study sheds new light on the transportation and sources of Hg in the subtropical forest ecosystems.展开更多
Commercial airline companies are continuously seeking to implement strategies for minimizing costs of fuel for their flight routes as acquiring jet fuel represents a significant part of operating and managing expenses...Commercial airline companies are continuously seeking to implement strategies for minimizing costs of fuel for their flight routes as acquiring jet fuel represents a significant part of operating and managing expenses for airline activities.A nonlinear mixed binary mathematical programming model for the airline fuel task is presented to minimize the total cost of refueling in an entire flight route problem.The model is enhanced to include possible discounts in fuel prices,which are performed by adding dummy variables and some restrictive constraints,or by fitting a suitable distribution function that relates prices to purchased quantities.The obtained fuel plan explains exactly the amounts of fuel in gallons to be purchased from each airport considering tankering strategy while minimizing the pertinent cost of the whole flight route.The relation between the amount of extra burnt fuel taken through tinkering strategy and the total flight time is also considered.A case study is introduced for a certain flight rotation in domestic US air transport route.The mathematical model including stepped discounted fuel prices is formulated.The problem has a stochastic nature as the total flight time is a random variable,the stochastic nature of the problem is realistic and more appropriate than the deterministic case.The stochastic style of the problem is simulated by introducing a suitable probability distribution for the flight time duration and generating enough number of runs to mimic the probabilistic real situation.Many similar real application problems are modelled as nonlinear mixed binary ones that are difficult to handle by exact methods.Therefore,metaheuristic approaches are widely used in treating such different optimization tasks.In this paper,a gaining sharing knowledge-based procedure is used to handle the mathematical model.The algorithm basically based on the process of gaining and sharing knowledge throughout the human lifetime.The generated simulation runs of the example are solved using the proposed algorithm,and the resulting distribution outputs for the optimum purchased fuel amounts from each airport and for the total cost and are obtained.展开更多
基金funded by the National Natural Science Foundation of China(No.41430754)。
文摘To understand its source,distribution,storage,and translocation in the subtropical forest ecosystems,mercury(Hg)concentrations and stable isotopes in forest biomass tissues(foliage,branch,bark,and trunk)were investigated at Ailao Mountain National Nature Reserve,Southwest China.The total Hg(THg)concentrations in the samples show the following trend:mature foliage(57±19 ng g-1)>bark(11±4.0 ng g-1)>branch(5.4±2.5 ng g-1)>trunk(1.6±0.7 ng g-1).Using the measured THg concentrations and the quantity of respective biomasses,the Hg pools in the forest are:wood(60±26μg m-2)>bark(51±18μg m-2)>foliage(41±11μg m-2)>branch(26±8.3μg m-2).The tree biomasses displayed negativeδ202Hg(-1.83‰to-3.84‰)andΔ199Hg(-0.18‰to-0.62‰).The observedΔ200Hg(-0.08‰to 0.04‰)is not significantly from zero.AΔ199Hg/Δ201Hg ratio of 1.05 was found in tree biomasses,suggesting that mercury has undergone Hg(Ⅱ)photoreduction processes.A Hg-isotope based binary mixing model suggests that Hg in the tree biomasses mainly originated from foliage uptake of atmospheric Hg0,constituting 67%,80%,and 77%of Hg in wood,branch,and bark,respectively.Our study sheds new light on the transportation and sources of Hg in the subtropical forest ecosystems.
基金The research is funded by Deanship of Scientific Research at King Saud University research group number RG-1436-040.
文摘Commercial airline companies are continuously seeking to implement strategies for minimizing costs of fuel for their flight routes as acquiring jet fuel represents a significant part of operating and managing expenses for airline activities.A nonlinear mixed binary mathematical programming model for the airline fuel task is presented to minimize the total cost of refueling in an entire flight route problem.The model is enhanced to include possible discounts in fuel prices,which are performed by adding dummy variables and some restrictive constraints,or by fitting a suitable distribution function that relates prices to purchased quantities.The obtained fuel plan explains exactly the amounts of fuel in gallons to be purchased from each airport considering tankering strategy while minimizing the pertinent cost of the whole flight route.The relation between the amount of extra burnt fuel taken through tinkering strategy and the total flight time is also considered.A case study is introduced for a certain flight rotation in domestic US air transport route.The mathematical model including stepped discounted fuel prices is formulated.The problem has a stochastic nature as the total flight time is a random variable,the stochastic nature of the problem is realistic and more appropriate than the deterministic case.The stochastic style of the problem is simulated by introducing a suitable probability distribution for the flight time duration and generating enough number of runs to mimic the probabilistic real situation.Many similar real application problems are modelled as nonlinear mixed binary ones that are difficult to handle by exact methods.Therefore,metaheuristic approaches are widely used in treating such different optimization tasks.In this paper,a gaining sharing knowledge-based procedure is used to handle the mathematical model.The algorithm basically based on the process of gaining and sharing knowledge throughout the human lifetime.The generated simulation runs of the example are solved using the proposed algorithm,and the resulting distribution outputs for the optimum purchased fuel amounts from each airport and for the total cost and are obtained.
