也谈经典力学的适用范围

现行高中物理课本说:“经典力学只适用于解决物体的低速运动问题,不能用来处理高速运动问题,经典力学只适用于宏观物体,一般不适用于微观粒子。”那么,怎样的物体是宏观物体?怎样的运动属于低速运动呢?     

经典力学的适用范围

在高一的物理课本中,学完牛顿运动定律后,总要提出它的适用范围——经典力学只适用于解决低速运动问题,不能用来处理高速运动的问题;经典力学只适用于宏观物体,一般不适用于微观粒子.宏观物体和微观物体     

混沌加密技术研究

混沌理论是近年来发展较快的非线性科学的重要分支,特别适用于数字通信和多媒体数据安全等领域。阐述了混沌的定义、混沌加密的应用以及几种典型的混沌加密模型。     

超混沌与保密通讯

阐明混沌与超混沌的主要区别,明确提出超混沌比混沌更适用于保密通讯的新观点     

动态力学

任何力均是两物体间的相互作用力,施力物体与受力物体并生并存,单独物体不能形成力,力必须依附于物体,不能凭空存在。光速不可超越是因为受力物体的速度不可能超过施力物体的速度,而施力物体受制于自身条件存在速度极限,就如一个人推车的速度不可能超过其跑步的最快速度。牛顿经典力学认为质量与速度无关是正确的,实验数据证明,当受力物体的速度接近施力物体的极限速度时,实际作用力变的非常小,使得速度很难进一步增加。动态力学的这一原理适用于任何力学现象,包括粒子加速器中的带电粒子,由于粒子加速器中的带电粒子不能超越光速并非因其质量增大,而是其实际受力随速度增加呈指数式衰减,故爱因斯坦狭义相对论的质能公式是错误的,牛顿经典力学认为能量与质量相互独立的理论是正确的。     

混沌现象在保密通信中的应用

简要介绍了混沌通信的发展概况,总结了混沌适用于保密通信的几个特点,重点阐述和分析了两大类混沌保密通信系统的应用方案。最后对混沌通信在实际应用中所需解决的问题进行了讨论。     

也谈“物体质量可变情况下的牛顿第二定律”

北京大学物理系蔡一坤等同志在《物理教学》1982年第2期上发表了一篇题为“物体质量可变情况下的牛顿第二定律”的文章。文中说:“……在经典力学范围内,讨论有关喷射、雨滴、滚雪球等所谓质量可变的物体时,把牛顿第二定律写成是错误的。”文中列举了伯克利物理学教程第一卷的公式(6—19)作为错误的一例。并且说:“这说明数学毕竟只是工具,只有了解物理过程的实质,才能正确地使用数学工具。”问题在于①式是否是错误的,是否不正确地使用了数学工具?或且是否如文中所说的“不是适用于变质量物体的一般公式。”让我们以该文中所列举的实验装置为例进行讨论(为便于对比,符号也尽可能用得一致),即:考虑一喷射机构,其质量是随时间减小     

关于加速度概念的地位意义

加速度是描述速度变化快慢的物理量。力学中二个最简单的积分,就可以充分说明它的重要性。这二个积分是: 根据①式,知道加速度(?)(t)和初速度(?)(o),就可以知道物体在任何时刻的速度(?)(t); 根据②式,知道(?)(t)和物体在初时刻的矢径(?)(o),就可以知道物体在任何时刻的矢径(?)(t),从而确定物体在任何时刻的位置。按经典力学的基本出发点:“知道物体在任一时刻的位置和速度”,就表示我们知道了物体的运动规律,或者说知道了物体的运动情况(见高中物理教科书上     

混沌同步的数字化信息保密通信方案设计

混沌同步应用于数字化信息保密通信中可提高通信安全。因此,对混沌保密通信技术进行分类阐述,设计基于统一混沌系统的同步控制器,并应用在混沌保密通信技术中,提出一种混沌保密通信方案。实验结果表明,该方案中同步控制器设计简单,同步速度快,恢复信号精度高,信道传输负担低,所设计的保密通信方案适用于数字化信息的适时保密通信。     

广义动能定理

§1 物体和物体系的广义功能在牛顿力学中,质点组的动能可以用下式来表示: K=∑1/2m_iu_i~2 (1)此式当然适用于若干粒子组成的热力学系统。若把分子作为质点看待,则一个物体便是     

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.     

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.     

团图为数的图中的闭团贯数

Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F.     

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?     

Social and Cultural Influence on Word Meaning

Different nations have different social cultures, and the social culture of every nation is developing with the development of the nation, language is greatly influenced by social culture, which enables language to possess national and historical characteristics. Word is the smallest, independent, meaningful linguistic unit of language. It can well reflect the national and historical characteristics. From synchronic aspect, the social and cultural influence on word meaning is mainly embodied in conceptual and associative meanings of word. The incorrespondence of word meaning is a phenomenon that exists in both conceptual and associative meanings of word among different languages. From diachronic aspect, the development of social culture causes some changes of word meaning to some extent. Therefore, social culture plays a key role in vocabulary learning and mastery of a language.     

汉字倒说

汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。     

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.