共查询到20条相似文献，搜索用时 78 毫秒
1.
通过计算7M 转动恒星在三种不同初始金属丰度下的非守恒演化模型,并进行比较,结果发现：金属丰度的大小不仅对转动恒星的演化寿命和在HR图中的演化轨迹有较大的影响,而且恒星金属丰度越大,在氦燃烧阶段的蓝回绕的长度越长;较大的金属丰度还会使核反应的产能率增大,从而影响恒星内部的中心温度、密度等其它物理量。 相似文献
2.
湍流应力对中等质量转动恒星演化的影响 总被引：3，自引：0，他引：3
以恒星结构与演化理论中常用的混合程理论为基础,将湍流应力和自转离心力引入传统恒星结构模型中的流体静力学平衡方程,得到了考虑湍流应力作用下转动恒星的结构模型.并计算了一8M⊙恒星从主序星到早期AGB星的演化.研究表明:湍流应力对恒星的结构并无明显的影响,但使得恒星在各个演化阶段的寿命发生不同程度的改变;而且对流区域越大,恒星的演化寿命变化越大;对恒星在AGB星以前的演化轨迹也无明显的影响,使AGB星在赫罗图中的演化向有效温度降低、表面光度降低方向偏转,更加接近观测事实. 相似文献
3.
考虑湍流应力作用下恒星的结构与演化模型,计算7M⊙早期AGB星在三个不同混合长参数α下的演化．研究表明：采用不同的混合长参数使氦燃烧反应的速率发生变化,导致恒星中心与表面元素的化学丰度有明显差别;混合长参数还影响了对流的传能作用,使早期AGB星在HR图中的演化轨迹、寿命及氦壳层内各物理量均显著不同． 相似文献
4.
简要地介绍了各种不同质量的恒星演化进程中各个主要热燃烧的点火条件及当前关于恒星演化的若干热点问题．分析了致密星物质中自由电子系统的简并性对星体热核燃烧的主导作用以及爆炸性核燃烧的条件。 相似文献
5.
自转恒星中各向异性的星风物质损失的研究 总被引：1，自引：1，他引：0
通过介绍忽略自转效应的恒星结构的一维模型与一维模型下星风物质损失的成功与不足,给出了考虑自转效应下恒星结构的二维模型与二维模型下星风物质损失. 相似文献
6.
吴济廉 《中国现代教育装备》2022,(8):31-33
针对以太阳和恒星作为参照物的区别,以及地球自转公转叠加等理解难点,自制太阳日与恒星日演示仪,旨在为学生模拟地球在不同运动方向下的公转自转,并直观展示太阳日与恒星日的形成及其差异. 相似文献
7.
为证明主序前星向零龄主序星演化过程中自转加快的理论预期,创新性的由强X-ray源选取11颗弱发射线T Tauri型星,并进行了多波段的测光观测.应用PDM和付理叶分析两种方法获得了其中6颗的光变周期,且多数短于1天.结果证明主序前恒星随星龄的增加自转加快,及金牛-御夫恒星形成区其星云中心的恒星明显的较外侧的恒星更为年轻. 相似文献
8.
9.
由于地球的自转、月球的公转以及地球的公转 ,产生了日月年的现象 ,因此有些人认为地球自转和月球公转以及地球公转的周期就等于日月年的时间 ,实际上它们并不完全相等而是相差一点 ,下面介绍一下它们的区别 .1 日的概念以地球自转运动周期为基础的时间单位叫日 .根据参考点的不同 ,有不同的“日” .以恒星为参考点的计日单位为恒星日 ,以太阳为参考点的计日单位为太阳日 .地球自转一周 36 0°所需的时间是 2 3时 5 6分 4秒 ,这叫做一个恒星日 ,这是地球自转的真正周期 .1天是2 4ｈ ,是太阳连续两次经过上中天的时间间隔叫做一个太阳日 ,一… 相似文献
10.
胡长茶 《数理天地(高中版)》2002,(3)
题目太阳现在处于主序星演化阶段,它主要是由电子和|H、|He等原子核组成.维持太阳辐射的是它内部的核聚变反应,核反应方程是2e+4}H-4/2He+释放的核能.根据目前关于恒星演化的理论,若由于聚变反应而使太阳中的H核数目从现有数减少10%,太阳将离开主序星阶段而转入红巨星的演化阶段.为了简化,假定目前太阳全部由电子和H核组成. 相似文献
11.
12.
13.
《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
14.
《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
15.
Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
16.
Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
17.
18.
RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
19.
20.
唐芳 《读与写:教育教学刊》2008,5(6)
During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context. 相似文献