“地球同步轨道”就是“地球静止轨道”吗?

人民教育出版社 1997年出版的高中《物理》第三册 (选修本 )第 96面关于通信卫星轨道的叙述中有这样一段话 :“通信卫星的轨道一般都采用‘地球静止轨道’,也称‘地球同步轨道’.即卫星转动的周期与地球自转的周期相同 ,相对于地球静止 .”这段话容易让人理解为 :地球同步轨道就是地球静止轨道 .处于同步轨道上的卫星相对于地球是静止的 .有的复习资料中亦有这样的练习题 :“简单说明地球同步卫星为什么只能在赤道平面内绕地球旋转 .”、“地球同步卫星相对于地球上的一点为什么是静止的 ?”,这也是将地球同步轨道与地球静止轨道混为一谈 .实际上 ,地球同步轨道与地球静止轨道不是一回事 ,它们之间有共同点也有较大区别 .地球同步轨道与地球静止轨道都是运行周期 ( 2 3小时 56分 0 4秒 )相同的人造地球卫星轨道 .这两种轨道的区别有三 :第一 ,轨道倾角有区别 .地球静止轨道是轨道倾角 (轨道平面和赤道平面的夹角 )为零的圆形地球同步轨道 .即地球静止轨道一定在赤道平面上 ;而地球同步轨道平面可与赤道平面成一不为零的夹角 .第二 ,观察者看到的现象不同 .在地球同步轨道上运行的卫星每天在相同时间经过相同地方的天空 ...     

有砟轨道和无砟轨道经济性研究分析

针对高速铁路,有砟轨道和无砟轨道各有优缺点.选取何种型式的轨道结构,考虑其经济性,是我国高速铁路建设中不可缺少的环节.本文分析了高速铁路轨道结构,尤其是无砟轨道与有砟轨道的经济性研究方法,并以实例加以说明.     

人造卫星的六个疑难问题

人造卫星是高科技的结晶,也是高考考查的热点.同学们复习时,应关注下列的六个疑难问题.一、人造地球卫星的运行轨道所谓人造地球卫星轨道就是人造地球卫星绕地球运行的轨道.这是一条封闭的曲线.这条封闭曲线形成的平面叫人造地球卫星的轨道平面,轨道平面总是通过地心,即可谓"两心重合,心心相映".     

浅谈分子轨道的对称性

1.分子轨道对称与反对称分子轨道是原子轨道的线性组合,除了在数学上用波函数表示外,通常用更形象的几何图形-分子轨道图形来表示,它能够更直观的显示出分子轨道的对称性.应用分子轨道对称守恒原理来说明反应机理时,通常是通过分析有关分子轨道图形的对称性来完成的.一个图形经过某些操作之后,能够完全恢复原来     

两种不能混为一谈的卫星轨道

现行高中物理 (选修本 )第三册 (人民教育出版社1 997年版 )第 96页指出 :“通信卫星的轨道一般都采用‘地球静止轨道’ ,也称‘地球同步轨道’ .即卫星转动的周期与地球自转的周期相同 ,相对于地球静止” .这段描述很容易让人们产生这样的错觉 :地球同步轨道就是地球静止轨道 ;处于同步轨道上的卫星相对地球是静止的 .另外一些文献[1] [2 ] [3] 中也将二者混为一谈 .其实 ,人造地球卫星的地球同步轨道与地球静止轨道除运行周期 (2 3小时 5 6分 0 4秒 )相同外 ,二者有较大的区别 .1　轨道倾角不同轨道倾角是卫星轨道平面与地球赤道平面的夹…     

高速铁路无砟轨道自密实混凝土施工研究

板式无砟轨道是一种全新的铁路轨道结构形式,它不同于传统有砟轨道,无须轨枕、散粒体碎石道床等结构支撑.自密实混凝土是板式无砟轨道结构的关键工程材料,其灌注施工质量直接决定板式无砟轨道结构整体质量.结合郑济铁路河南段现场施工经验,探讨了自密实混凝土和配制要求,总结了高速铁路无砟轨道自密实混凝土施工要点,希望对同类工程施工有一定参考和借鉴.     

人造探测器撞向彗星

彗星是什么 彗星是形状不规则的天体,由冰冻着的各种杂质、尘埃组成.其轨道有椭圆、抛物线、双曲线三种.椭圆轨道的彗星又叫周期彗星,另两种轨道的叫非周期彗星.     

氨基甲烷到氨基戊烷加、减电子对HOMO、LUMO的影响

采用HF方法,在最小基组条件下,研究了氨基甲烷到氨基戊烷加电子或减电子对其最高占据轨道和最低未占据轨道的影响.结果表明：该系列物质加电子是加载在最低非占据轨道上,减电子是减在最高占据轨道上.     

湿陷性黄土区客运专线沉降监测分析与工程应用

无碴轨道是保证高速铁路运行的一种轨道铺设形式,其铺设条件评估的重点是线下工程的沉降变形.郑西客运专线正是采用这种轨道铺设形式,要做好郑西客运专线施工期间的沉降观测,就必须对沉降观测资料进行分析,预测工后沉降,确定无碴轨道的铺设时间,确保无碴轨道结构的安全.     

如果小球放低点…(高一、高二、高三)

题如图1,小球质量为m,沿光滑的斜轨道由静止滑下.圆形轨道半径为R.要使小球沿光滑圆轨道恰能通过最高点.问小球应从斜轨道上何处开始滑下?解设小球从斜轨道上距最低点h高处滑下,取最低点为零势点,则所以h=-5/2R.这是一道很常见的题.如果小球放得再低点,情况     

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?     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

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.     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.     

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…