The self-excited DC air circuit breaker(SE-DCCB)has been widely used in urban rail transit due to its excellent stability.It can realize forward and reverse interruption,but has difficulty interrupting small currents ...The self-excited DC air circuit breaker(SE-DCCB)has been widely used in urban rail transit due to its excellent stability.It can realize forward and reverse interruption,but has difficulty interrupting small currents due to the phenomenon of arc root sticking at the entrance of the arc chamber in the splitting process,which is known as arc root stagnation.A coupling model of the self-excited magnetic field and magnetohydrodynamics is established for the SE-DCCB with the traditional structure.The magnetic field,temperature and airflow distribution in the arc chamber are investigated with an interrupting current of 150 A.The simulation results show that the direction and magnitude of the magnetic blowout force are the dominant factors in the arc root stagnation.The local high temperature of the arc chamber due to arc root stagnation increases the obstruction effect of the airflow vortex on the arc root movement,which significantly increases the arc duration time of small current interruption.Based on the research,the structure of the magnetic conductance plate of the actual product is improved,which can improve the direction and magnitude of the magnetic blowout force at the arc root so as to restrain the development of the airflow vortex effectively and solve the problem of arc root stagnation when the small current is interrupted.The simulation results show that the circuit breaker with improved structure has a better performance for a small current interruption range from 100 A to 350 A.展开更多
To reduce the influence of adverse flow conditions at the fan hub and improve fan aerodynamic performance, a modification of conventional axial fan blades with numerical and experimental investigation is presented. Ho...To reduce the influence of adverse flow conditions at the fan hub and improve fan aerodynamic performance, a modification of conventional axial fan blades with numerical and experimental investigation is presented. Hollow blade root is manufactured near the hub. The numerical and experimental results show that hollow blade root has some effect on the static performance. Static pressure of the modified fan is generally the same with that of the datum fan, while, the efficiency curve of the modified fan has a different trend with that of the datum fan. The highest efficiency of the modified fan is 10% greater than that of the datum fan. The orthogonal experimental re- suits of fan noise show that hollow blade root is a feasible method of reducing fan noise, and the maximum value of noise reduction is about 2 dB. The factors affecting the noise reduction of hollow blade root are in the order of importance as follows： hollow blade margin, hollow blade height and hollow blade width. The much smoother pressure distribution of the modified fan than that of the datum fan is the main mechanism of noise reduction of hollow blade root. The research results will provide the proof of the parameter optimization and the structure de- sign for high performance and low noise small axial fans.展开更多
Background:Thinning is a commonly used treatment in forest management which affects the tree root systems.The effects of thinning on element concentrations and seasonal change of roots were evaluated in adjacent oak(Q...Background:Thinning is a commonly used treatment in forest management which affects the tree root systems.The effects of thinning on element concentrations and seasonal change of roots were evaluated in adjacent oak(Quercus frainetto Ten.)and hornbeam(Carpinus betulus L.)stands according to the different root diameter classes.Method:Two replicated control and thinning plots(50m×50 m)were set for each species(hornbeam and oak).Thinning treatments(November 2010)reduced 50%of the basal area in both oak and hornbeam stands.Roots were assessed by seasonal collection over 2 years(from October 2010 to October 2012).The roots were then sorted into diameter classes of 0–2mm(fine roots),2–5mm(small roots)and>5mm(coarse roots).C,N,P,K,Ca,Na,Mg,S,Mn,Fe,Al,Zn,Pb,Ni,Cu and Cd were analyzed.Results:Except coarse roots,the highest root biomasses were determined in April-2011 in all plots.Fine-root biomass in oak was found significantly higher in control plots.In contrast to the oak,the fine-root biomass in the thinned hornbeam plots was higher than in the controls.The small-root biomass did not significantly differ between the thinned and the control plots in both oak and hornbeam stands.However,the coarse-root biomass showed significant differences between the control(1989 g∙m^(−2))and thinned plots(1060 g∙m^(−2))in oak,while no difference was detected in hornbeam.The concentrations of C,Al,Pb,Cd,Ni,Zn,Mn,Na,K,Mg and P in the fine roots of oak were significantly higher in the thinned plots.However,the concentration of Pb,Cd and Fe in the fine roots was significantly higher in the thinned plots of hornbeam.Significant differences were observed between the species for all elements in the fine roots except for C,N and P.In particular,elements in the fine roots tended to increase in July in the oak.In the hornbeam,all element concentrations in the fine roots(except C,N,and S)in the thinned plots showed a tendency to increase in April.The concentrations of Pb,Ni,Al,Fe,Cu,Ca,Na,K,Mg and P in the hornbeam control plots in展开更多
Many small RNAs have been confirmed to play important roles in the development of root nodules and arbuscular mycorrhiza. In this study, we carried out the identification of certain small RNAs in leguminous plants(Med...Many small RNAs have been confirmed to play important roles in the development of root nodules and arbuscular mycorrhiza. In this study, we carried out the identification of certain small RNAs in leguminous plants(Medicago truncatula, soybean, peanut and common bean), such as miRNAs, tRFs and srRNAs, as well as the computational investigation of their regulations. Thirty miRNAs were predicted to be involved in establishing root nodules and mycorrhiza, and 12 of them were novel in common bean and peanut. The generation of tRFs in M. truncatula was not associated with tRNA gene frequencies and codon usage. Six tRFs exhibited different expressions in mycorrhiza and root nodules. Moreover, srRNA^(5.8S) in M. truncatula was generated from the regions with relatively low conservation at the rRNA 3′ terminal. The protein-protein interactions between the proteins encoded by the target genes of miRNAs, tRFs and srRNAs were computed. The regulation of these three types of sRNAs in the symbiosis between leguminous plants and microorganisms is not a single regulation of certain signaling or metabolic pathways but a global regulation for the plants to own growth or specific events in symbiosis.展开更多
Small peptides function as key signals in processes,such as plant cell differentiation,organ development and defenses to biotic stresses.A large number of small peptide precursor genes have been predicted from the ana...Small peptides function as key signals in processes,such as plant cell differentiation,organ development and defenses to biotic stresses.A large number of small peptide precursor genes have been predicted from the analysis of the soybean(Glycine max) whole genome DNA sequence.However,most of these genes have unknown characteristics and functions.In this report,we systemically searched for the gene families of small peptide precursors that are up-regulated in soybean nitrogen-fixing root nodules.We found 212 genes(encoding peptides shorter than 150 amino acids) that were up-regulated,and among them,79 genes belong to 38 multiple-gene families,but the other 133 genes are unique.Twenty-eight of 38 families are conserved in Arabidopsis,but the other 10 only exist in legumes.We also identified 16 out of the 38 members of the wound-induced polypeptide(WIP) gene family to be upregulated in nitrogen-fixing nodules.We further analyzed homologs of WIP genes in Medicago,Lotus,Arabidopsis and Oryza species and found that a few homologous genes from Medicago truncatula and Lotus japonicus were also upregulated in their nodules and some WIP genes were induced by specific fungal pathogens on soybean and rice.Structure prediction indicated that all WIP prepropeptides contain a conserved DUF3774 domain(including two hydrophobic regions) and most of them have an N-terminal signal sequence.Fluorescence microscopy analysis of two WIP prepropeptides fused to GFP revealed that these proteins are located on the plasma membrane of tobacco leaf cells.Interestingly,34 soybean WIP genes are clustered onto three soybean chromosomes,different from known peptide gene families(such as CLE).Among them,11 highly identical genes are aligned on the 6th chromosome,12 on the 12th,and 11 on the 13th chromosomes.Most of WIP genes from the 12th chromosome share the highest identities with their homologs on the 13th chromosome,suggesting that ancestral WIP genes could have originated from the 13th chromosome,then spread onto the 12th chromosome by chrom展开更多
基金supported by National Natural Science Foundation of China(No.51977132)the Key Special Science and Technology Project of Liaoning Province(No.2020JH1/10100012)the General Program of the Education Department of Liaoning Province(No.LJKZ0126).
文摘The self-excited DC air circuit breaker(SE-DCCB)has been widely used in urban rail transit due to its excellent stability.It can realize forward and reverse interruption,but has difficulty interrupting small currents due to the phenomenon of arc root sticking at the entrance of the arc chamber in the splitting process,which is known as arc root stagnation.A coupling model of the self-excited magnetic field and magnetohydrodynamics is established for the SE-DCCB with the traditional structure.The magnetic field,temperature and airflow distribution in the arc chamber are investigated with an interrupting current of 150 A.The simulation results show that the direction and magnitude of the magnetic blowout force are the dominant factors in the arc root stagnation.The local high temperature of the arc chamber due to arc root stagnation increases the obstruction effect of the airflow vortex on the arc root movement,which significantly increases the arc duration time of small current interruption.Based on the research,the structure of the magnetic conductance plate of the actual product is improved,which can improve the direction and magnitude of the magnetic blowout force at the arc root so as to restrain the development of the airflow vortex effectively and solve the problem of arc root stagnation when the small current is interrupted.The simulation results show that the circuit breaker with improved structure has a better performance for a small current interruption range from 100 A to 350 A.
基金supported by National Natural Science Foundation of China(No.51249003,No.51006090)Major Special Project of Technology Office in Zhejiang Province(No.2011C16038,No.2011C11073)
文摘To reduce the influence of adverse flow conditions at the fan hub and improve fan aerodynamic performance, a modification of conventional axial fan blades with numerical and experimental investigation is presented. Hollow blade root is manufactured near the hub. The numerical and experimental results show that hollow blade root has some effect on the static performance. Static pressure of the modified fan is generally the same with that of the datum fan, while, the efficiency curve of the modified fan has a different trend with that of the datum fan. The highest efficiency of the modified fan is 10% greater than that of the datum fan. The orthogonal experimental re- suits of fan noise show that hollow blade root is a feasible method of reducing fan noise, and the maximum value of noise reduction is about 2 dB. The factors affecting the noise reduction of hollow blade root are in the order of importance as follows： hollow blade margin, hollow blade height and hollow blade width. The much smoother pressure distribution of the modified fan than that of the datum fan is the main mechanism of noise reduction of hollow blade root. The research results will provide the proof of the parameter optimization and the structure de- sign for high performance and low noise small axial fans.
基金This work was supported by Scientific Research Projects Coordination Unit of Istanbul University-Cerrahpasa(Project No.FYD-2016-20102).
文摘Background:Thinning is a commonly used treatment in forest management which affects the tree root systems.The effects of thinning on element concentrations and seasonal change of roots were evaluated in adjacent oak(Quercus frainetto Ten.)and hornbeam(Carpinus betulus L.)stands according to the different root diameter classes.Method:Two replicated control and thinning plots(50m×50 m)were set for each species(hornbeam and oak).Thinning treatments(November 2010)reduced 50%of the basal area in both oak and hornbeam stands.Roots were assessed by seasonal collection over 2 years(from October 2010 to October 2012).The roots were then sorted into diameter classes of 0–2mm(fine roots),2–5mm(small roots)and>5mm(coarse roots).C,N,P,K,Ca,Na,Mg,S,Mn,Fe,Al,Zn,Pb,Ni,Cu and Cd were analyzed.Results:Except coarse roots,the highest root biomasses were determined in April-2011 in all plots.Fine-root biomass in oak was found significantly higher in control plots.In contrast to the oak,the fine-root biomass in the thinned hornbeam plots was higher than in the controls.The small-root biomass did not significantly differ between the thinned and the control plots in both oak and hornbeam stands.However,the coarse-root biomass showed significant differences between the control(1989 g∙m^(−2))and thinned plots(1060 g∙m^(−2))in oak,while no difference was detected in hornbeam.The concentrations of C,Al,Pb,Cd,Ni,Zn,Mn,Na,K,Mg and P in the fine roots of oak were significantly higher in the thinned plots.However,the concentration of Pb,Cd and Fe in the fine roots was significantly higher in the thinned plots of hornbeam.Significant differences were observed between the species for all elements in the fine roots except for C,N and P.In particular,elements in the fine roots tended to increase in July in the oak.In the hornbeam,all element concentrations in the fine roots(except C,N,and S)in the thinned plots showed a tendency to increase in April.The concentrations of Pb,Ni,Al,Fe,Cu,Ca,Na,K,Mg and P in the hornbeam control plots in
基金supported by the National Natural Science Foundation of China(31371328,31571366,31470191)the Science and Technology Project of Zhejiang Province(2013C3303,2014C33019)Project of Jiangxi Academy of Science(2014-XTPH1-09,2014-YYB-09)
文摘Many small RNAs have been confirmed to play important roles in the development of root nodules and arbuscular mycorrhiza. In this study, we carried out the identification of certain small RNAs in leguminous plants(Medicago truncatula, soybean, peanut and common bean), such as miRNAs, tRFs and srRNAs, as well as the computational investigation of their regulations. Thirty miRNAs were predicted to be involved in establishing root nodules and mycorrhiza, and 12 of them were novel in common bean and peanut. The generation of tRFs in M. truncatula was not associated with tRNA gene frequencies and codon usage. Six tRFs exhibited different expressions in mycorrhiza and root nodules. Moreover, srRNA^(5.8S) in M. truncatula was generated from the regions with relatively low conservation at the rRNA 3′ terminal. The protein-protein interactions between the proteins encoded by the target genes of miRNAs, tRFs and srRNAs were computed. The regulation of these three types of sRNAs in the symbiosis between leguminous plants and microorganisms is not a single regulation of certain signaling or metabolic pathways but a global regulation for the plants to own growth or specific events in symbiosis.
基金supported by National Key Basic Research Program of China(2011CB100702 and 2010CB126501)National Natural Science Foundation of China(31070218)+1 种基金Shanghai Municipal Natural Science Foundation(09ZR1436500)Knowledge Innovation Program of Chinese Academy of Sciences(2009KIP206)
文摘Small peptides function as key signals in processes,such as plant cell differentiation,organ development and defenses to biotic stresses.A large number of small peptide precursor genes have been predicted from the analysis of the soybean(Glycine max) whole genome DNA sequence.However,most of these genes have unknown characteristics and functions.In this report,we systemically searched for the gene families of small peptide precursors that are up-regulated in soybean nitrogen-fixing root nodules.We found 212 genes(encoding peptides shorter than 150 amino acids) that were up-regulated,and among them,79 genes belong to 38 multiple-gene families,but the other 133 genes are unique.Twenty-eight of 38 families are conserved in Arabidopsis,but the other 10 only exist in legumes.We also identified 16 out of the 38 members of the wound-induced polypeptide(WIP) gene family to be upregulated in nitrogen-fixing nodules.We further analyzed homologs of WIP genes in Medicago,Lotus,Arabidopsis and Oryza species and found that a few homologous genes from Medicago truncatula and Lotus japonicus were also upregulated in their nodules and some WIP genes were induced by specific fungal pathogens on soybean and rice.Structure prediction indicated that all WIP prepropeptides contain a conserved DUF3774 domain(including two hydrophobic regions) and most of them have an N-terminal signal sequence.Fluorescence microscopy analysis of two WIP prepropeptides fused to GFP revealed that these proteins are located on the plasma membrane of tobacco leaf cells.Interestingly,34 soybean WIP genes are clustered onto three soybean chromosomes,different from known peptide gene families(such as CLE).Among them,11 highly identical genes are aligned on the 6th chromosome,12 on the 12th,and 11 on the 13th chromosomes.Most of WIP genes from the 12th chromosome share the highest identities with their homologs on the 13th chromosome,suggesting that ancestral WIP genes could have originated from the 13th chromosome,then spread onto the 12th chromosome by chrom
