Distributed generation has attracted great attention in recent years, thanks to the progress in new-generation technologies and advanced power electronics. And micro-grid can make full use of distributed generation, s...Distributed generation has attracted great attention in recent years, thanks to the progress in new-generation technologies and advanced power electronics. And micro-grid can make full use of distributed generation, so it has been widespread concern. On the other hand due to the extensive use of power electronic devices and many of the loads within micro-grid are nonlinear in nature, Micro-grid generate a large number of harmonics, so harmonics pollution needs to be addressed. Usually we use passive filter to filter out harmonic, in this paper, we propose a new method to optimize the filter parameters, so passive filter can filter out harmonic better. This method utilizes immune particle swarm optimization algorithm to optimize filter parameters. It can be shown from the simulation results that the proposed method is effective for micro-grid voltage harmonics compensation.展开更多
Cr(Ⅵ)and phenol are toxic contaminants that need to be treated,and different methods have been researched to simultaneously remove these two contaminants from industrial wastewater.In this study,Cr(Ⅵ)was used as a n...Cr(Ⅵ)and phenol are toxic contaminants that need to be treated,and different methods have been researched to simultaneously remove these two contaminants from industrial wastewater.In this study,Cr(Ⅵ)was used as a novel Fenton-like catalyst in phenol degradation by H2O2.In the pH range of 3.0-11.0,the degradation efficiency of phenol decreased with elevated pH.At pH=3.0,100 mg/L phenol was effectively degraded by 2 mmol/L Cr(Ⅵ)and 20 mmol/L H2O2.At pH=7.0 and the same conditions as those of pH=3.0,79%of 100 mg/L phenol was removed within 6h,which was an improvement in pH limitation compared with the Fe(Ⅱ)-mediated Fenton reaction.Quenching experiments indicated that·OH generated from the catalysis of H2O2 by Cr(Ⅴ)instead of Cr(Ⅵ)was the primary oxidant that degraded phenol.When pyrophosphate was added in the Cr(Ⅵ)/H2O2 system,complexes with the Cr(Ⅴ)intermediate rapidly formed and inhibited H2O2 decomposition,implying that the decomposition of H2O2 to·OH was catalyzed by Cr(Ⅴ)instead of Cr(Ⅵ).The presence of anions such as chloride and sulfate had insignificant effect on the degradation of phenol.TOC and UV analyses suggest that phenol could not be completely oxidized to CO2 and H2O,and the intermediates identified by high performance liquid chromatography further indicates that maleic acid and benzoquinone were intermediates which may be further degraded into short chain acids,primarily maleic,formic,acetic,and oxalic acids,and eventually into CO2 and H2O.Considering that more than 50%Cr(Ⅵ)can also be removed during this process,the Cr(Ⅵ)/H2O2 system is more appropriate for the simultaneous removal of Cr(Ⅵ)and phenol contaminants from industrial wastewater.展开更多
The timing of flowering(FL)and leaf unfolding(LU)determine plants’reproduction and vegetative growth.Global warming has substantially advanced FL and LU of temperate and boreal plants,but their responses to warming d...The timing of flowering(FL)and leaf unfolding(LU)determine plants’reproduction and vegetative growth.Global warming has substantially advanced FL and LU of temperate and boreal plants,but their responses to warming differ,which may influence the time interval between FL and LU(ΔLU-FL),thereby impacting plant fitness and intraspecific physiological processes.Based on twigs collected from two flowering-first tree species,Populus tomentosa and Amygdalus triloba,we conducted a manipulative experiment to investigate the effects of winter chilling,spring warming and photoperiod on theΔLU-FL.We found that photoperiod did not affect theΔLU-FL of Amygdalus triloba,but shortenedΔLU-FL by 5.1 d of Populus tomentosa.Interestingly,spring warming and winter chilling oppositely affected theΔLU-FL of both species.Specifically,low chilling accumulation extended theΔLU-FL by 3.8 and 9.4 d for Populus tomentosa and Amygdalus triloba,but spring warming shortened theΔLU-FL by 4.1 and 0.2 d℃^(-1).Our results indicate that climate warming will decrease or increase theΔLU-FL depending on the warming periods,i.e.,spring or winter.The shifted time interval between flowering and leaf unfolding may have ecological effects including affecting pollen transfer efficiency and alter the structure and functioning of terrestrial ecosystem.展开更多
文摘Distributed generation has attracted great attention in recent years, thanks to the progress in new-generation technologies and advanced power electronics. And micro-grid can make full use of distributed generation, so it has been widespread concern. On the other hand due to the extensive use of power electronic devices and many of the loads within micro-grid are nonlinear in nature, Micro-grid generate a large number of harmonics, so harmonics pollution needs to be addressed. Usually we use passive filter to filter out harmonic, in this paper, we propose a new method to optimize the filter parameters, so passive filter can filter out harmonic better. This method utilizes immune particle swarm optimization algorithm to optimize filter parameters. It can be shown from the simulation results that the proposed method is effective for micro-grid voltage harmonics compensation.
基金supported by the National Natural Science Foundation of China (No. 41373114 and 51508384)the Natural Science Foundation of Tianjin (No. 15JCZDJC40200)the Foundation of Key Lab of Indoor Air Environment Quality Control (Tianjin University)
文摘Cr(Ⅵ)and phenol are toxic contaminants that need to be treated,and different methods have been researched to simultaneously remove these two contaminants from industrial wastewater.In this study,Cr(Ⅵ)was used as a novel Fenton-like catalyst in phenol degradation by H2O2.In the pH range of 3.0-11.0,the degradation efficiency of phenol decreased with elevated pH.At pH=3.0,100 mg/L phenol was effectively degraded by 2 mmol/L Cr(Ⅵ)and 20 mmol/L H2O2.At pH=7.0 and the same conditions as those of pH=3.0,79%of 100 mg/L phenol was removed within 6h,which was an improvement in pH limitation compared with the Fe(Ⅱ)-mediated Fenton reaction.Quenching experiments indicated that·OH generated from the catalysis of H2O2 by Cr(Ⅴ)instead of Cr(Ⅵ)was the primary oxidant that degraded phenol.When pyrophosphate was added in the Cr(Ⅵ)/H2O2 system,complexes with the Cr(Ⅴ)intermediate rapidly formed and inhibited H2O2 decomposition,implying that the decomposition of H2O2 to·OH was catalyzed by Cr(Ⅴ)instead of Cr(Ⅵ).The presence of anions such as chloride and sulfate had insignificant effect on the degradation of phenol.TOC and UV analyses suggest that phenol could not be completely oxidized to CO2 and H2O,and the intermediates identified by high performance liquid chromatography further indicates that maleic acid and benzoquinone were intermediates which may be further degraded into short chain acids,primarily maleic,formic,acetic,and oxalic acids,and eventually into CO2 and H2O.Considering that more than 50%Cr(Ⅵ)can also be removed during this process,the Cr(Ⅵ)/H2O2 system is more appropriate for the simultaneous removal of Cr(Ⅵ)and phenol contaminants from industrial wastewater.
基金the National Funds for Distinguished Young Scholar(42025101)the International Cooperation and Exchanges NSFC-FWO(32111530083)the 111 Project(B18006)。
文摘The timing of flowering(FL)and leaf unfolding(LU)determine plants’reproduction and vegetative growth.Global warming has substantially advanced FL and LU of temperate and boreal plants,but their responses to warming differ,which may influence the time interval between FL and LU(ΔLU-FL),thereby impacting plant fitness and intraspecific physiological processes.Based on twigs collected from two flowering-first tree species,Populus tomentosa and Amygdalus triloba,we conducted a manipulative experiment to investigate the effects of winter chilling,spring warming and photoperiod on theΔLU-FL.We found that photoperiod did not affect theΔLU-FL of Amygdalus triloba,but shortenedΔLU-FL by 5.1 d of Populus tomentosa.Interestingly,spring warming and winter chilling oppositely affected theΔLU-FL of both species.Specifically,low chilling accumulation extended theΔLU-FL by 3.8 and 9.4 d for Populus tomentosa and Amygdalus triloba,but spring warming shortened theΔLU-FL by 4.1 and 0.2 d℃^(-1).Our results indicate that climate warming will decrease or increase theΔLU-FL depending on the warming periods,i.e.,spring or winter.The shifted time interval between flowering and leaf unfolding may have ecological effects including affecting pollen transfer efficiency and alter the structure and functioning of terrestrial ecosystem.
