求微分方程变传递函数，详细过程，感激不尽

以一个二阶线性常微分方程为例说明求传递函数的过程：
系统的输入函数：x(t)；系统的输出函数为：y(t)；对应的微分方程为：
ay +by+cy = px +qx (1)
a,b,c,p,q 均为常数；一撇表一阶导数、两撇表二阶导数。
对微分方程(1)两边作拉氏内变换：
(as²+bs+c)Y(s) = (ps+q)X(s) (2)
其中Y(s)、X(s)分别为输出和输入函数的拉氏变换。
由(2)可以解出(1)的传递函容数：
H(s)＝Y(s)/X(s) = (ps+q)/(as²+bs+c) (3)
即微分方程输出的拉氏变换与输入的拉氏变换之比
即为传递函数。

什么是说课标，说教材

一、“说课标、说教材”活动的十个具体要求：
1、说本学科的课程总目标或学段目标。
2、说本学段或本册书或一个单元的内容标准。
3、说教材的编写特点、编排体例、内容结构。如有条件可把不同版本的教材进行比较。
4、说知识和技能的立体式整合。既能在横向上按照教材编排顺序说明逻辑序列，又能按照知识大类把整个学段（或相邻年级）的同类知识作简要纵向整合。
5、说教学建议。根据课程标准和所用教材的特点，谈具体的教学建议。
8、要能脱稿演讲（包括少看银幕和荧屏），内容熟练。
9、要语言流畅，简洁、生动，教态自然大方。
10、要以幻灯片制作以知识树为主，文字较少。清晰、大方、有新意。
二、说教材应注意的问题：
首先，教师要把握整个学段的教材。每个学段的教师，不管是教哪个年级的，都要把本学科的整个学段的教材拿到手，对照新课标认真的研读，在理解的基础上画出知识树，并写出教材分析。其次，要把握一册教材。一个真正有经验的教师首先要通读整册课本，对照新课标，了解编者的意图和知识的前后联系，画出整册书的知识结构图，写出教材分析。按照前边的路子仍然以备课组为单位进行研讨，共同设计出本册课本的知识结构图张贴于教室墙壁。在新学期的开始不要急于讲第一课，而是给学生讲整册课本的知识结构和学习计划。第三，要把握一个单元的教材。教师在备课时不要只备一节教材或一篇课文，而要备一个单元。新的课程标准指导下的各科教材基本都是按照主题的形式来编排的。教师在备课时首先要明确一个单元的主题，清楚编者围绕这一主题是如何选材和编排的。要提倡教师单元备课，集体备课，把一个单元的课时和活动整体安排。
通过“同课异构”活动，探讨高效的课堂模式，转变师生的教学方式，落实第二个支点。通过“导学教学案”的使用，引导学生自读文本，让学生“查、划、写、记、练、思”培养学生自学能力。在课堂上教师引导学生树立“八种意识”，培养“七种习惯”，教会学生学习的方法。学生自学能力的培养，科学的学习方法养成不是一日之功，需要教师不断地用心训练和指导。

如何用英语介绍赵州桥

Zhaozhou Bridge
The Zhaozhou Bridge (traditional Chinese: 赵州桥; simplified Chinese: 赵州桥; pinyin: Zhàozhōu Qiáo) is the worlds oldest open-spandrel stone segmental arch bridge.[1] Credited to a craftsman named Li Chun, the bridge was constructed in the years 595-605 during the Sui Dynasty. Located in the southern part of Hebei Province, it is the oldest standing bridge in China, although the Chinese had built bridges over waterways since the ancient Zhou Dynasty.
Name and location
The Zhaozhou Bridge is also known as the Safe Crossing Bridge (traditional Chinese: 安济桥; simplified Chinese: 安济桥; pinyin: An Ji Qiáo, englished as the Anji Bridge) and the Great Stone Bridge (Chinese: 大石桥; pinyin: Dà Shí Qiáo). It crosses the Xiao River (traditional Chinese: ; simplified Chinese: 洨河; pinyin: Xiào Hé, Jiao He) in Zhao County, approximately 40 km southeast of the provincial capital Shijiazhuang. It is named for the nearby Zhao County (赵县), which was formerly known as Zhaozhou (赵州).
Construction
The Zhaozhou Bridge is about 50 m long with a central span of about 37 m. It stands 7.3 m tall and has a width of 9 m. The arch covers a circular segment less than a semicircle and has a rise-to-span ratio of approximately 1:5 (7.3 to 37 m). This is considerably smaller than the rise-to-span ratio of 1:2 of a semicircular arch bridge and subjects the abutments of the bridge to large forces.
The central arch is made of 28 thin, curved limestone slabs which are joined with iron dovetails. This allows the arch to adjust to shifts in its supports, and prevents the bridge from collapsing even when a segment of the arch breaks. The bridge has two small side arches on either side of the main arch. These side arches serve two important functions: First, they reduce the total weight of the bridge by about 15.3% or approximately 700 tons, which is vital because of the low rise-to-span ratio and the large forces on the abutments it creates. Second, when the bridge is submerged during a flood, they allow water to pass through, thereby reducing the forces on the structure of the bridge.
Li Chuns innovative spandrel-arch construction, while economising in materials, was also of considerable aesthetic merit. An inscription left on the bridge by Tang officials seventy years after its construction reads:
“ This stone bridge over the Jiao River is the result of the work of the Sui engineer Li Chun. Its construction is indeed unusual, and no-one knows on what principle he made it. But let us observe his marvellous use of stone-work. Its convexity is so smooth, and the wedge-shaped stones fit together so perfectly... How lofty is the flying-arch! How large is the opening, yet without piers!.. Precise indeed are the cross-bondings and joints between the stones, masonry blocks delicately interlocking like mill wheels, or like the walls of wells; a hundred forms (organised into) one. And besides the mortar in the crevices there are slender-waisted iron cramps to bind the stones together. The four small arches inserted, on either side two, break the anger of the roaring floods, and protect the bridge mightily. Such a master-work could never have been achieved if this man had not applied his genius to the building of a work which would last for centuries to come.[2] ”
Later history and reputation
In the next 1400 years, the bridge survived at least eight wars, ten major floods and numerous earthquakes, the nearest of which being the 7.2 degree Xingtai Earthquake in 1966. Yet, the support structure remains intact and the bridge is still in use. Only the ornamental railings have been replaced every few hundred years.
The intriguing design of the bridge has given rise to many legends. According to one legend, the bridge was built by a master architect named Lu Ban in a single night. In another story, the bridge was put to the test by two immortals who crossed it at the same time and Lu Ban saved it by wading into the water and supporting the structure.
Although Ming Dynasty authors compared the bridge to "a new moon rising above the clouds" and "a long rainbow hanging on a mountain waterfall"[2], it later fell into obscurity. When Professor Liang Sicheng (梁思成) of Tsing Hua University rediscovered the bridge on a field exploration of ancient architecture in Hebei province, made detailed measurements, and published a report and drawing ("An Chi Chiao the Great Stone Bridge Chao Hsien, Hobei, Sui Dynasty AD 569-617, Li Chun Master Builder"), it became world famous.
Zhaozhou Bridge was dedicated as an International Historic Civil Engineering Landmark by the American Society of Civil Engineers in 1991. The Chinese authorities nominated it for incription on the World Heritage List as having "a very important place in the world bridge building history".[2]
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You can tell your friend to google it online--Zhaozhou Bridge.

培训方式有几种形式

为开展业务及培育人才的需要，采用各种方式对员工进行有目的、有计划的培养和训练的管理活动。
员工培训的9种形式
　　1、讲授法
　　属于传统的培训方式，优点是运用起来方便，便于培训者控制整个过程。缺点是单向信息传递，反馈效果差。常被用于一些理念性知识的培训。
　　2、视听技术法
　　通过现代视听技术(如投影仪、DVD、录像机等工具)，对员工进行培训。优点是运用视觉与听觉的感知方式，直观鲜明。但学员的反馈与实践较差，且制作和购买的成本高，内容易过时。它多用于企业概况、传授技能等培训内容，也可用于概念性知识的培训。
　　3、讨论法
　　按照费用与操作的复杂程序又可分成一般小组讨论与研讨会两种方式。研讨会多以专题演讲为主，中途或会后允许学员与演讲者进行交流沟通。优点是信息可以多向传递，与讲授法相比反馈效果较好，但费用较高。而小组讨论法的特点是信息交流时方式为多向传递，学员的参与性高，费用较低。多用于巩固知识，训练学员分析、解决问题的能力与人际交往的能力，但运用时对培训教师的要求较高。
　　4、案例研讨法
　　通过向培训对象提供相关的背景资料，让其寻找合适的解决方法。这一方式使用费用低，反馈效果好，可以有效训练学员分析解决问题的能力。另外，近年的培训研究表明，案例、讨论的方式也可用于知识类的培训，且效果更佳。
　　A、优点：
　　a.可以帮助学员学习分析问题和解决问题的技巧;
　　b.能够帮助学员确认和了解不同解决问题的可行方法。
　　B、局限性：
　　a.需要较长的时间;
　　b.可能同时激励与激怒不同的人;
　　c.与问题相关的资料有时可能不甚明了，影响分析的结果。
　　5、角色扮演法
　　授训者在培训教师设计的工作情况中扮演其中角色，其他学员与培训教师在学员表演后作适当的点评。由于信息传递多向化，反馈效果好、实践性强、费用低，因而多用于人际关系能力的训练。
　　A、优点：
　　a.能激发学员解决问题的热情;
　　b.可增加学习的多样性和趣味性;
　　c.能够激发热烈的讨论，使学员各抒己见;
　　d.能够提供在他人立场上设身处地思考问题的机会;
　　e.可避免可能的危险与尝试错误的痛苦。
　　B、局限性：
　　a. 观众的数量不宜太多;
　　b.演出效果可能受限于学员过度羞怯或过深的自我意识。
　　C、培训时应注意的问题：
　　a.要准备好场地与设施，使演出学员与观众之间保持一段距离;
　　b.演出前要明确议题所遭遇的情况;
　　c.谨慎挑选演出学员与角色分配;
　　d.鼓励学员以轻松的心情演出;
　　e.可由不同组的学员重复演出相同的情况;
　　f.可安排不同文化背景的学员演出，以了解不同文化的影响。
　　6、自学法
　　这一方式较适合于一般理念性知识的学习，由于成人学习具有偏重经验与理解的特性，让具有一定学习能力与自觉的学员自学是既经济又实用的方法，但此方法也存在监督性差的缺陷。
　　7、互动小组法
　　也称敏感训练法。此法主要适用于管理人员的人际关系与沟通训练。让学员在培训活动中的亲身体验来提高他们处理人际关系的能力。其优点是可明显提高人际关系与沟通的能力，但其效果在很大程度上依赖于培训教师的水平。
　　8、网络培训法
　　是一种新型的计算机网络信息培训方式，投入较大。但由于使用灵活，符合分散式学习的新趋势，节省学员集中培训的时间与费用。这种方式信息量大，新知识、新观念传递优势明显，更适合成人学习。因此，特别为实力雄厚的企业所青睐，也是培训发展的一个必然趋势。
　　9、个别指导法
　　师徒传承也叫“师傅带徒弟”、“学徒工制”、“个别指导法”，是由一个在年龄上或经验上资深的员工，来支持一位较资浅者进行个人发展或生涯发展的体制。师傅的角色包含了教练、顾问以及支持者。身为教练，会帮助资浅者发展其技能，身为顾问，会提供支持并帮助他们建立自信;身为支持者，会以保护者的身份积极介入各项事务，让资浅者得到更重要的任务，或运用权力让他们升迁、加薪。
　　优点：
　　a.在师傅指导下开始工作，可以避免盲目摸索;
　　b.有利于尽快融入团队;
　　c.可以消除刚刚进入工作的紧张感;
　　d.有利于传统的优良工作作风的传递;
　　e.可以从指导人处获取丰富的经验。