白矮星的结构特点

用Fowler提出的理论推导了白矮星的质量-半径关系和极限质量，并讨论了白矮星的内部压强和密度分布。     

白矮星的质量上限

本文讨论了恒星内部电子兼并压强的公式，然后在此基础上进一步研究白矮星，给出了白矮星质量上限的一个简化推导。     

浅谈白矮星和中子星的密度及由来

现用新编初中物理课本第一册“密度”一节中,以现代物理知识窗口的形式介绍了白矮星和中子星的密度:“水是地球上常见的物质,宇宙中的白矮星密度大约是水的100万倍,中子星的密度大约是白矮星的1亿倍。”地球上的水是以分子状态存在常压下的,典型密度是1克/厘米~3。白矮星中的物质主要是以原子核状态和电子简并态存在的。其典型密度为10~6克/厘米~3的数量级,理论上可达10~6～10~(11)克/厘米~3。     

迟到的诺贝尔奖

印度人苏布拉马尼扬·钱德拉塞卡聪慧过人,19岁时便奇迹般地演算出一个惊人的结果:当恒星质量超过某一上限时,它的最终归宿将不会是白矮星。这与当时天体物理学界的观点针锋相对。那时的科学家坚持,恒星的白矮星阶段被认为是一切恒星演化过程的最终阶段。后来,钱德拉塞卡以优异的成绩获得奖学金,到英国剑桥大学求学。     

恒星的演化与物理过程

在天文学的研究中,致密天体的研究成为20世纪最为活跃的研究领域,本文在恒星演化及物理过程的阐述中着重介绍了致密天体白矮星、中子星和黑洞的产生和演化.     

太阳会爆炸吗

太阳是银河系中的一颗恒星,是一个炽热的气体球。根据不同的体积和不同的质量,恒星的归宿也各不相同。质量较大的星球寿命比较短,当它们度过自己的一生后,就会以爆炸的形式自我毁灭。几十亿年后,太阳会变成一颗膨胀的红巨星,进入激烈活动的时代,但膨胀的程度并不会那么剧烈,就像天琴座的环状星云,扩展着肥皂般的气壳,然后变成白矮星,不久便会冷却下来。太阳会爆炸吗     

恒星演化

简单叙述了恒星的诞生、演化及衰亡 ,展示了恒星的存在历程 ,同时表明了恒星这类重要天体的起源及演化规律。描绘出了恒星在星际气体尘埃中诞生 ,在主星序阶段稳定演化 ,最后以白矮星 ,中子星或黑洞告终的一生经历轮廓。     

恒星演化

简单叙述了恒星的诞生、演化及衰亡，展示了恒星的存在历程，同时表明了恒星这类重要天体的起源及演化规律。描绘出了恒星在星际气体尘埃中诞生，在主星序阶段稳定演化，最后以白矮星，中子星或黑洞告终的一生经历轮廓。     

恒星的一生

恒星是由星际弥漫物质在万有引力作用下集聚形成的,由氢氦元素的聚变反应热维持其生命过程。在历经主序星、红巨星和白矮星或中子星后演化为致密星体而结束一生。这种演化过程对应着它在赫罗图上位置的规律性变动。     

恒星的一生

恒星是由星际漫物质在万有引力作用下集聚形成的，由氢氦元素的聚变反应热维持其生命过程，在历经主序星，红巨星和白矮星或中子星后演化为致密星体而结束一生。这种演化过程对应着它在赫罗图上位置的规律性变动。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

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?     

只要努力,不要后悔

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.     

浅谈移民问题

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.     

Sister Carrie, an Adherent of Desires

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.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

胡主席在印度,我却在中国

Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer.