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数学钟时间顺序控制器的改进
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作者 丘双安 王荣 《电世界》 1993年第10期16-17,共2页
关键词 数学钟 时间顺序 控制器
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数学探究性学习一例
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作者 温上伟 李桂生 《数学学习与研究》 2010年第7期13-13,共1页
本文以新课程标准为导向,根据生活实际,提出钟面数学问题,并从学习内容、学习过程、课后练习、课后评价等方面入手,探讨探究性学习的学习方式。
关键词 探究性学习 数学问题 夹角 由大到小 数学实验 教学评价
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Realization of population inversion between 7S_(1/2) and 6P_(3/2) levels of cesium for four-level active optical clock 被引量:6
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作者 WANG YanFei WANG DongYing +5 位作者 ZHANG TongGang HONG YeLong ZHANG ShengNan TAO ZhiMing XIE XiaoPeng CHEN JingBiao 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2013年第6期1107-1110,共4页
We demonstrate experimentally the population inversion between 7S1/2 and 6P3/2 levels of cesium in thermal cesium cell with a 455.5 nm pumping laser.We calculate the relative population probabilities at each level the... We demonstrate experimentally the population inversion between 7S1/2 and 6P3/2 levels of cesium in thermal cesium cell with a 455.5 nm pumping laser.We calculate the relative population probabilities at each level theoretically with the density matrix method.In a steady state,5.8% atoms are at 7S1/2 level and 2.9% at 6P3/2 level,which builds up the population inversion between the two levels.We obtain the fluorescence spectra produced in thermal cesium cell in our experiment.The measured relative intensity of each available fluorescence spectral line in the experiment agrees very well with the theoretical result.The demonstrated population inversion between 7S1/2 and 6P3/2 levels can be used to construct an active optical clock of four-level system with a wavelength of 1469.9 nm. 展开更多
关键词 active optical clock four-level system population inversion
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Ding w-Flat Modules and Dimensions
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作者 Fuad Ali Ahmed Almahdi Mohammed Tamekkante 《Algebra Colloquium》 SCIE CSCD 2018年第2期203-216,共14页
The introduction of w-operation in the class of flat modules has been successful. Let R be a ring. An R-module M is called a w-fiat module if Tor1r(M, N) is GV-torsion for all R-modules N. In this paper, we introduc... The introduction of w-operation in the class of flat modules has been successful. Let R be a ring. An R-module M is called a w-fiat module if Tor1r(M, N) is GV-torsion for all R-modules N. In this paper, we introduce the w-operation in Gorenstein homological algebra. An R-module M is called Ding w-flat if there exists an exact sequence of projective R-modules ... → P1 → P0 → p0 → p1 → ... such that M Im(P0 → p0) and such that the functor HomR (-,F) leaves the sequence exact whenever F is w-flat. Several well- known classes of rings are characterized in terms of Ding w-flat modules. Some examples are given to show that Ding w-flat modules lie strictly between projective modules and Gorenstein projective modules. The Ding w-flat dimension (of modules and rings) and the existence of Ding w-flat precovers are also studied. 展开更多
关键词 w-fiat module and dimension Gorenstein projective module and dimension strongly Gorenstein flat module
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