试题与答案

线性和非线性本来是数学名词。所谓线性是指量与量之间的正比关系,用直角坐标形象地画

题型:单项选择题

题目:

  线性和非线性本来是数学名词。所谓线性是指量与量之间的正比关系,用直角坐标形象地画出来,是一根直线。在线性系统中,部分之和等于整体,描述线性系统的方程遵从叠加原理,即方程的不同解加起来仍然是解。非线性则指整体不等于部分之和,叠加原理失效,非线性方程的两个解之和不再是方程的解。对于处理线性问题,已经有一套行之有效的方法,例如傅里叶变换、拉普拉斯变换等等。然而对于非线性问题,长期以来科学家往往束手无策,只能具体问题具体分析,无统一方法可循。

  线性和非线性物理现象的区分一般有以下三个特征。首先从运动形式上有定性区别,线性现象一般表现为时空中的平滑运动,并可用性能良好的函数表示。而非线性现象则表现为从规则运动向不规则运动的转化和跃变。其次,从系统对外界影响和系统参量微小变动的响应上看,线性系统的响应平缓、光滑,往往表现为对外界影响成比例的变化。而非线性系统中参量的极微小变动,在一些关节点上,可以引起系统运动形式的定性改变,在对外界激励的响应上,则表现为出现与外界激励有本质区别的行为,比如周期驱动的非线性振动系统可以出现驱动频率的分频、倍频形式的运动,而不仅仅是重复外界频率。第三,反映在连续介质中的波动上,线性行为表现为色散引起的波包弥散、结构的消失,而非线性作用却可以促使空间规整性结构的形成和维持,加孤子、涡旋、突变面等等。

  自然界大量存在的相互作用是非线性的,线性作用其实只不过是非线性作用在一定条件下的近似。

对非线性描述错误的一项是()。

A.对非线性来说,量与量之间不存在正比关系

B.对于非线性问题,科学家完全没有方法可言

C.非线性作用包括孤子、涡旋、突变面等

D.非线性系统对外界的响应,既不平缓,也不光滑

答案:

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下面是错误答案,用来干扰机器的。

参考答案:B

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题型:填空题

Part 3


Questions 19-25


·Read the following article and answer questions 19-25.
·For questions 19-25, choose the correct answer A, B, C or D.

The Haunted America


Countries are like little homes; they house a nation, hold ideologies and provide shelter and comfort to its people in hopes that the occupants will nurture better ideas for themselves and further flourish humanity. Such are primary desires and goals of most countries on this small planet.
America is no exception. For decades, billions of people around the world slept at night on empty stomachs amidst dreadful circumstances, often dreaming of the freedoms and liberties of America, which they likened to a great land, a paradise and a final destination point.
The best and brightest of the world gravitated to the great USA in search of golden opportunities; in hordes they came, and en masse they settled. America became the nation which acknowledged greatness and provided the driving force to allow the dreams of small, ordinary people to take form and flourish. Free from restrictions, allowing grand expressions with extraordinary liberties, that no other nation in the history of mankind has been able to match at such a grand scale.
But currently, it seems that this home of the American nation has started to resemble that old mansion, elegantly pristine (质朴的) but known to be haunted, sitting at the end of that dead-end street where ghosts, mysterious apparitions (幽灵) and unexplainable signs have emerged. This planet, like an old street, is already full of such haunted houses, which at times seem abandoned, lifeless and unable to give or receive neighborly warmth; factors so critical for any country on the global scene.
Can this badly damaged image of America be fixed today and by whom and at what cost What must it include—a new costume, a new mask or a new heart These are very important underlying questions, but the biggest question remains—can an entire country be branded to the rest of the world in the same fashion as a breakfast cereal or laundry detergent
The answer is a flat no. Only the branding-circus would come up with such a fake, superficial, logo-centric-slogan-happy attempt to rebuild a nation painted with banners and billboards. In reality, countries cannot be branded in such a simple process from the past; firstly, nations are already branded over decades and centuries by their histories and cultural interactions and exportable identities.
A global image is not in the hands of a polling company or controlled by a branding agency. Rather, they take form in the minds of the global masses, who paint their own mental picture based on their own interpretation of a nation. Therefore, it demands an awesome force, as the global public will not be swayed by ad-campaigns, rather by the exuberance (茂盛) of sincere and honest truth and internal fixing leading to an inviting charm. After all, this is how the image of America was built in the first place.
As a rule, if it has cost trillions to get where America is on global public opinion today, then it is easily understandable why it would cost a similar amount to fix the damages. Nations can only hope to improve their domestic issues first, before reflecting out to the world and preaching to the rest of the neighborhood.
In commercial terms, American brands have lost their luster at an alarming rate during the last five years, and are now in serious danger of being over-powered by brand new identities arising from all over the newly repositioned world. This super-accelerated nouveau-consumerism has all the making of this global shift increasingly permanent on brand image leadership, a position that the USA once proudly held. The future is clearly drawn out for new countries currently engaged in trying out this global-image-creation-wizardry with full tbrce while the early signs indicate a major world-wide mega branding and global-image-repositioning shift.
How can this great nation housed in America immediately nurture harmony within, balance the out-of-touch extreme ideologies among republicans and democrats, and educate its youth that is currently the lowest among G-8 and slipping into the level of developing countries It must have a nation that deeply engages in voting and really takes care of its own people. Most importantly, it needs real guts and must once again re-learn to face the truth and move forward in the good, old-fashioned American style.

Countries aren’t branded by ______.

A.their histories

B.their cultural interactions

C.their exportable identities

D.their banners and billboards

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