Density waves in 3D spiral galaxies are studied.In order to eliminate the forbidden region near the corotation in the grand-design galaxies,we assume that the perturbation satisfies the stable condition Q(r)>1 over...Density waves in 3D spiral galaxies are studied.In order to eliminate the forbidden region near the corotation in the grand-design galaxies,we assume that the perturbation satisfies the stable condition Q(r)>1 over all the disk except that at the corotation.Then,a new method is put forward here to determine some basic parameters of spiral galaxies.We apply it to our Galaxy,and the results are in good agreement with the previous results.展开更多
This letter is emphasized on the discussion of the group velocity of disturbed galactic density waves(GDW),which is one of the two most insurmountable problems in the density waves theory.In our calculation,we find th...This letter is emphasized on the discussion of the group velocity of disturbed galactic density waves(GDW),which is one of the two most insurmountable problems in the density waves theory.In our calculation,we find that the galactic thickness has an important effect on the GDW.The dynamic time scale of GDW in our three-dimensional model can be prominently prolonged,from 36%to 60%contrasting to that of two-dimensional galactic model.However,it is still less than the lifetime of our Galaxy,which means that it is necessary to seek some other physical mechanisms to excite and sustain the GDW.展开更多
In order to reduce the water shrinkage of rabbit hair knitted fabrics, a new method is developed, which is blending rabbit hairs with a little bit of blaze. The sericin on the blaze which can swell and melt in hot and...In order to reduce the water shrinkage of rabbit hair knitted fabrics, a new method is developed, which is blending rabbit hairs with a little bit of blaze. The sericin on the blaze which can swell and melt in hot and wet condition can cohere the rabbit hairs through special processing. So the relative movement among fibers could be restricted. The testing results show that the water shrinkage of rabbit hair knitted fabrics can be greatly reduced after processed.展开更多
基金Supported in part by the National Natural Science Foundation of China under Grant No.19873005the Director Foundation of National Education Ministry(9528424)the National Climbing Project on Fundamental Researches.
文摘Density waves in 3D spiral galaxies are studied.In order to eliminate the forbidden region near the corotation in the grand-design galaxies,we assume that the perturbation satisfies the stable condition Q(r)>1 over all the disk except that at the corotation.Then,a new method is put forward here to determine some basic parameters of spiral galaxies.We apply it to our Galaxy,and the results are in good agreement with the previous results.
基金Supported in part by the National Natural Science Foundation of China under Grant No.19873005the Director Foundation of National Education Ministry(9528424)the National Climbing Project on Fundamental Researches.
文摘This letter is emphasized on the discussion of the group velocity of disturbed galactic density waves(GDW),which is one of the two most insurmountable problems in the density waves theory.In our calculation,we find that the galactic thickness has an important effect on the GDW.The dynamic time scale of GDW in our three-dimensional model can be prominently prolonged,from 36%to 60%contrasting to that of two-dimensional galactic model.However,it is still less than the lifetime of our Galaxy,which means that it is necessary to seek some other physical mechanisms to excite and sustain the GDW.
文摘In order to reduce the water shrinkage of rabbit hair knitted fabrics, a new method is developed, which is blending rabbit hairs with a little bit of blaze. The sericin on the blaze which can swell and melt in hot and wet condition can cohere the rabbit hairs through special processing. So the relative movement among fibers could be restricted. The testing results show that the water shrinkage of rabbit hair knitted fabrics can be greatly reduced after processed.
