In this paper we study the existence of FIn-envelopes, FI1/n-envelopes and FIn-covers, where FIn denotes the class of all n-absolute pure modules for an integer n 〉 0 or n = ∞. We prove that FI1/n-envelopes and FIn-...In this paper we study the existence of FIn-envelopes, FI1/n-envelopes and FIn-covers, where FIn denotes the class of all n-absolute pure modules for an integer n 〉 0 or n = ∞. We prove that FI1/n-envelopes and FIn-covers exist over an n-coherent ring R, and FIn-covers and special FIn-preenvelopes exist over any ring R.展开更多
Beta spiral technique can be used to determine the three dimensional velocity field , usually in the open ocean , as functions of depth at a single location. This work is aimed at applying the method to the lower laye...Beta spiral technique can be used to determine the three dimensional velocity field , usually in the open ocean , as functions of depth at a single location. This work is aimed at applying the method to the lower layers in the western boundary area of the Pacific at two locations covered by 5 CTD stations each , and then using the results to study the vertical structure of the western boundary current in the Pacific .展开更多
It Is known for a long time that basing on low—resolution“whole Sun”measurements at various frequencies made at different observatories,a spectrum of radioburst could be plotted,and some parameters of spectrum,f<...It Is known for a long time that basing on low—resolution“whole Sun”measurements at various frequencies made at different observatories,a spectrum of radioburst could be plotted,and some parameters of spectrum,f<sub>max</sub>-the frequency of peakflux density in a spectrum;spectral slope below f<sub>max</sub>;and spectral slope above f<sub>max</sub>,areparticularly valuable as a solar flare diagnostic,in particular for a dynamic spectrum.展开更多
文摘In this paper we study the existence of FIn-envelopes, FI1/n-envelopes and FIn-covers, where FIn denotes the class of all n-absolute pure modules for an integer n 〉 0 or n = ∞. We prove that FI1/n-envelopes and FIn-covers exist over an n-coherent ring R, and FIn-covers and special FIn-preenvelopes exist over any ring R.
基金Contribution No.1776 from the Institute of Oceanology, Academia Sinica. This work is supported by NSFC (No. 4880230).
文摘Beta spiral technique can be used to determine the three dimensional velocity field , usually in the open ocean , as functions of depth at a single location. This work is aimed at applying the method to the lower layers in the western boundary area of the Pacific at two locations covered by 5 CTD stations each , and then using the results to study the vertical structure of the western boundary current in the Pacific .
文摘It Is known for a long time that basing on low—resolution“whole Sun”measurements at various frequencies made at different observatories,a spectrum of radioburst could be plotted,and some parameters of spectrum,f<sub>max</sub>-the frequency of peakflux density in a spectrum;spectral slope below f<sub>max</sub>;and spectral slope above f<sub>max</sub>,areparticularly valuable as a solar flare diagnostic,in particular for a dynamic spectrum.
