plecture4
lecture-4-英语词汇记忆与语法
Tense
Comments on writing
But in the past many years, children had another kind of lifestyle, they had several brothers and sisters. And their parents needed to take care of several children at the same time, so they couldn’t be looked after well like the children who live in the modern time, but they had fine childhoods what they thought of.
When I was a child, I always wear my mother clothes are done, or my brother wearing a small, not clothes. About one year to get a new clothes until my high school age in 1983.
pronoun
我 你 他 她 它 我们 你们 他们
主格
I you he she it we you they
宾格
me you him her it us you them
形容词性 所有格
my your his her its our your their
名词性 所有格
mine yours his hers its ours yours theirs
The postman is always putting your letters into my letter-box. (不满情 绪)；
Lecture 4. Comparative Statics of Demand 范里安版《中级微观经济学》ppt
y p1x1*
x2* 0
12
Examples of Income Changes
Perfect Substitutes
x2
Engel curve
y
for good 1
Choice with p1 < p2
y
x1*
Engel curve
for good 2
Income offer curve
x1 0
y
x2*
Engel curve
for good 1
x1
x1*
17
Income Effects
◊ Recall: If the demand for a good rises with income, it is a normal good.
◊ There are two kinds of normal goods. ◊ If the demand for a good goes up by a
6
Engel curve
◊ A plot of quantity demanded against
income is called an Engel curve.
x2
Fixed p1 and p2.
y’ < y’’ < y’’’ y
Income offer
curve
y’’’
y’’’ x’’’ y’’ x’’
18
Income Changes:
One Normal and One Inferior
x2
Income offer curve
y
Engel curve
for good 2
Luxury Good
新编大学英语(第四版)视听说教程3教学课件U4
like snowstorms, extremely strong winds and low temperatures. On top of that, we are often working in an environment where there’s very little oxygen available. Host: So the body is exposed to altitude sickness?
Name of explorer
Country of birth
Year of birth Major
exploration(s) Interesting facts
Warming up
12 Throughout human history, explorers have made discoveries that changed the way we viewed the world. Now you are going to learn about great explorers in history or modern times.
Step 2 Each of you comes up with three true / false questions or short answer questions about the explorer you described. Ask your group members the questions to check their understanding of your description.
Lecture 4 Phonology
4.What is minimal pairs
Minimal pairs: When two different forms are identical in every way except for one sound segment which occurs in the same place in the strings, the two sounds combinations are said to form a minimal pair. pit/bit; rapid/rabid; Cap/cab/
Pool, leaf Peak, speak
Allophones: The phones that can represent a phoneme are called allophones. (一个音位所代表 的两个或几个不同的音素,也就是同一个音位的各个音 称为该音位的音位变体.)e.g. “pill” and “spill”, in the word “pill” [p]需要吐气,因为这个音位在元
How many phones are there in the following words? feel ; like; pit; spit
A phoneme is a phonological unit . It is a unit of distinctive value. Look at the two words: ―pat‖ and ―bat‖, What is the difference between the two words? So in English the sounds (phones) that possess the distinctive value are called phonemes.Phonemes are said to be the distinctive sounds.
常微分方程及动力系统4
(2)As for Uniqueness of solution,we use Gronwall’s inequality through proof by contra-
diction.
For more details of the proof, see ref[1, 2]
1.1 The contraction Mapping Theorem
Proof:By integrating,we have
t
y(t) = y0 + f (y(s)) ds
t0
This
is
the
integral
form
of
the
differential
equation
dy dt
=
f (y)
sufficing
the
initial
condition
i.e y(t0) = y0.Thus the integral and differential forms of this equation are equivalent.To proof
the existence and uniqueness of Solution to Initial value problem of (1.1),we use the integral
form
(1)As for Existence of solution,we could construct Picard-iteration series.
3. M d=ef sup |f (y)(t)|
y∈[y0−b,y0+b]
4.
Choose
T
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b M
fluent12-lecture04-boundary-conditions_M
Boundary Conditions
建议(General Guidelines)
• 尽量将边界条件设置在流体充分流出
或流进计算域的位置.
– 并非必需, 但是具有更好的收敛效果.
Training Manual
Upper pressure boundary modified to ensure that flow always enters domain.
4-13
April 28, 2009 Inventory #002600
Boundary Conditions
压力出口(Pressure Outlet)
• 适用于可压缩及不可压缩流.
– 超音速出口时,忽略定义的压力. – 在外流或非受限流动中可作为自由边界使用.
Training Manual
• 需要输入的信息：
• 多孔介质是一种特殊的流体域
– 在 Fluid 面板中激活多孔介质域 – 通过用户输入的集总阻力系数来确定流动方向的压降
• 用来模拟通过多孔介质，或者流
动阻力均匀的物体内的流动
– 填充床 – 孔板 – 流动分布器
– 管束
• 输入粘性系数和惯性阻力系数.
ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved.
速度入口(Velocity Inlet)
• 均匀速度入口可通过以下方式定义：
– Magnitude, Normal to Boundary
Training Manual
– Components
– Magnitude and Direction
• 可使用UDF或profile定义非均匀流. • 速度入口主要用在不可压缩流中, 在 可压缩流中不推荐使用.
lecture用法最全详解(含习题)
2.lecturelecture /ˈlektʃə(r)/ 词频4n. 讲座；讲课；教训. vi. (开)讲座；讲课. vt. 训斥派：lecturer 词频2 n.演讲者；（大学）讲师①高义频vi.&n.（尤指大学中的）讲座；讲课；演讲go to/attend a lecture 听讲座deliver/give a lecture做讲座a lecture on/about 关于……的讲课/训斥e.g. He lectures on literature at Manchester University. 他在曼彻斯特大学教文学。
②低义频vi.&n.教训；训斥lecture sb. about/on...因……训斥某人give sb. a lecture 给某人一个教训e.g. He’s always lecturing me about the way I dress. 他总是对我的穿着说三道四。
e.g. I know I should stop drinking-don’t give me a lecture about it.我知道我该戒酒，别教训我了。
1.单词拼写（1）I went to the ___(讲座) he gave in the hall.(lecture)（2）He learned a ___(教训)from this thing-he should stop smoking for his health.(lecture)（3）Professor Smith will give a l___ in Fudan University this evening about the history of English.(lecture)（4）She suffered a bad cold. As a result, she missed the ___(讲座) she liked very much.(lecture)（5）She preferred that we should have the discussion right after the ___(讲座).(lecture)（6）Please stop___(lecture) me! I know I should quit smoking.2.语法填空（1）The ___ (lecture) spoke very clearly so that we could hear every word.(lecturer) 3. 完成句子（1）He ___ ___ ___ ___time management to first-year students___ ___ ___ ___.他在报告厅给一年级学生做关于时间管理的讲座。
TPO-40托福听力题目文本——对话部分（Conversation）【附答案】
TPO-40托福听力题目文本——对话部分(Conversation)【附答案】托福TPO，英文名为TOEFL Practice Online，中文直译为托福线上练习，TPO都是历年托福真题，对托福备考是非常有帮助的，今天为大家分享的是TPO-40托福听力题目文本——对话部分(Conversation)【附答案】。
TPO-40托福听力题目文本——对话部分(Conversation)【附答案】QUESTIONS1. Why does the student go to see the professor?a. To find out all the requirements for a projectb. To discuss a service gap at a restaurantc. To get help understanding concepts relevant to his projectd. To get help with designing a business plan2. Why does the professor mention a student in another class?a. To describe an interesting topic for a projectb. To explain the cause of her initial confusionc. To point out that she has not received e-mails from all her students yetd. To indicate that she has several students doing projects about restaurans托福听力主旨题的答题技巧新托福听力考试总共有六大技巧的测试与考核。
与这六大技巧相对，ETS有六大题型的测试，分别是：主旨题、细节题、句子功能题、态度题、结构题和推论题。
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第五节：五单元复相系的热力学平衡条件和稳定条件 平衡的稳定条件举例:利用内能的判据(其它判据也可以导出来相应的公式!):20,0,U U δδ=>i i i i i i iiiU U T S P V N δδδδμδ==-+∑∑2222i i i i i i i i i i i iiU T S P V N T S P V N δδδμδδδδδδμδ=-++-+∑0V S N δδδ===约束条件120V V V δδδ=+=利用等约束条件0,,i i i U T T P P δμμ=→===222121200V V V V V V δδδδδδ=+=⇒=+=()()()2221211211210;T T S P P V N δδμμδ⇒---+-=2;i i i i i i iU T S P V N δδδδδδμδ⇒=-+∑,;,.i i i i i i i i i i i i i i i i S N s S N s N s V N v V N v N v δδδδδδ==+==+()()2i i i i i i i i i i iiiU N T s P v s T v P N δδδδδδδδμδ⇓=-+-+∑∑0i i i i i s T v P δδδμ-+=热力学基本方程()2i i i i i iU N T s P v δδδδδ⇒=-∑i i i i T s P v δδδδ->故对任意指数i, 0T s P v δδδδ->简写为用T,v 做独力变量来表达上式：;;v v T vv Ts s c P s T v T v T v T T P P P T v T v δδδδδδδδ∂∂∂⎛⎫⎛⎫⎛⎫=+=+ ⎪ ⎪ ⎪∂∂∂⎝⎭⎝⎭⎝⎭∂∂⎛⎫⎛⎫=+ ⎪ ⎪∂∂⎝⎭⎝⎭()()22v Tc P T s P v T v T v δδδδδδ∂⎛⎫-=- ⎪∂⎝⎭0,0v TP c v ∂⎛⎫⇒>< ⎪∂⎝⎭0T s P v δδδδ->可以证明其它稳定条件(选择不同独立变量)，并证明这些条件是等价的. 如0,0P sv c P ∂⎛⎫>< ⎪∂⎝⎭20,0,0U U V S N δδδδδ=>===Remark:只能确定能量是不是极小, 不能确定是不是最小. 如果是极小,不是最小, 这些态是亚稳态.在系统涨落较小的情况下, 亚稳态也是稳定的. 如果系统涨落比较大, 亚稳态是有有限的寿命.课外思考：磁性系统的稳定性的讨论M. Plischke and B. Bergersen, Equilibrium Statistical Physics参考此书第一章第七节单元复相系平衡条件过去我们是研究物质处于一种物态, 我们称之为单相. 系统也可以同时处于多种物态(多种物态共存,比如冰和水),称为多相或复相.化学纯物质(只有一个组元或一种分子),只含有一个化学纯物质情况下称为单元系.考虑单元系系统处于复相. 相i 的内能,体积,粒子数为 ,,i i iU V N20,0;0;,,.i i i iiiS S U V N U U V V N N δδδδδ=<======∑∑∑我们下面利用熵判据得到系统的平衡条件:()1i i i i i i i i iS U P V N T δδδμδ=+-∑∑代入可以用拉氏乘子法考虑约束条件()1231230;i i i i iS U V N S U V N δλλλδλδλδλδ---=---=∑1231,,P T T Tμλλλ⇒===,,.i i i T T P P μμ⇒===,-00.i j i j i T T U U dS U dUδδδ>=<⇒>=如果虚过程变为实过程第六节：相变热力学平衡相变相：在不同温度和压强范围，一个单元系可以分别处在气相，液相，固相.不同物态或者相(phase):同一金属低温下铁磁体，高温是顺磁体.金属与合金在高温是正常态金属，低温是超导体.固相也可以有不同的晶体结构。
这些不同的晶体结构也是不同相。
如高压冰，迄今为止发现16种晶格态冰和三种非晶格态冰(/water/phase.html).水的简单相图C O相图2各种神奇形状的雪花水的p,v,T 面.P,T相图p,v相图T,V相图系统中物理性质均匀部分叫做相。
相是按物理性质不同来划分的.在不同的外界条件下, 物态呈现不同的相.热力学不能解释这些现象,这是统计力学要解决的问题.一般物态在低温下是有序态,比如晶格态.高温下是无序态, 比如气态和液态.在更加低温情况下, 有些系统会有超导现象发生.对简单PV 系统，不同相达到平衡时(既单元系2相共存).压强温度满足两相平衡方程：()();;,,i j i j i j T T P P T P T P μμ===水的相图, 存在固液(溶解线)共存线,气液(气化线)共存线,固气(升华线) 共存线,及其三条线的交点(三相点).1.在平衡曲线上,温度和压强两个参量只有一个可以独立改变.2.曲线上两相的化学势相等. 两相可按任意比例共存. 整个系统的吉布斯函数是相等的.水的p,v 相图平衡相变:当系统缓慢地从外界吸收或者放出热量时，物质将从一个相转变到另外一个相而始终保持平衡态。
故称为平衡相变.平衡相变潜热(一级相变.相变级数定义下面会讲到)一级相变的特点：1.相变过程中系统与外界有热交换. 1摩尔物质从i 相转变为j 相所吸收的热量. 由于过程是等温可逆, 故吸收的热量为:()j i L T s s =-L 称为潜热. 潜热的存在表明, 两相的摩尔熵不等. 2.从一个相转变为另外一个相时，物质的摩尔体积也发生变化。
如水100C,气压1.013×105Pℎ下变成蒸汽时，体积增加1600多倍. 克拉珀龙方程在两相平衡曲线的热上，相变平衡条件：()()()()()(),,,,,,,i j i j T P T dT P dP T P T P T dT P dP T dT P dT μμμμ++⇓=++=++如在相变曲线上()()()()()(),,,,,,i i i j j j T dT P dP T P d T P d T P T dT P dP d T P μμμμμμ++-===++-()(),,i i i j j j d T P s dT v dP d T P s dT v dPμμ=-+==-+⇓热力学方程()j i j i j i s s dP L dT v v T v v -==-- 克拉珀龙方程克拉珀龙方程适用于一级相变. 二级相变有类似方程(以后会再提到)。
克拉珀龙（Benoit Pierre Emile Clapeyron,1799～1864）法国物理学家和土木工程师。
主要从事热学、蒸汽机设计和理论、铁路工程技术方面研究。
他设计了法国第一条铁路线。
在设计计算中发明了以他命名的支撑力矩计算法。
1799年1月26日生于巴黎。
1818年毕业于巴黎工艺学院。
1820～1830年在俄国彼得堡交通工程部门担任工程师，在铁路部门有较大贡献。
回到法国后，1844年起任巴黎桥梁道路学校教授。
1848年被选为巴黎科学院院士。
1834年赋予卡诺理论以易懂的数学形式，使卡诺理论显出巨大意义。
1834年克拉珀龙还由气体的实验定律归纳出了理想气体的状态方程，这个方程1874年被门捷列夫推广，故称为克拉珀龙-门捷列夫方程。
相变级数的定义:在相变平衡曲线上各相化学势相等,但摩尔熵不等,摩尔体积也不等,;;.i j j i i j P P j i i j T Ts s T T v v P P μμμμμμ=∂⎛⎫∂⎛⎫≠⇒≠⎪ ⎪∂∂⎝⎭⎝⎭∂⎛⎫∂⎛⎫≠⇒≠⎪ ⎪∂∂⎝⎭⎝⎭即相变时,化学势相等,但其一级导数不连续.这种相变称为一级相变. 如果一级导数连续, 二级导数不连续,则称为二级相变, 等等.克拉珀龙方程应用举例 潜热沿相变曲线的变化(){}j i j i j i j j i i j i P T P T d T s s ds dL ds s s T dT dT dT dT s s dP s s dP s s T T P dT T P dT -⎛⎫==-+- ⎪⎝⎭⎛⎫∂∂⎡⎤⎛⎫⎛⎫∂∂⎛⎫⎛⎫=-++-+ ⎪ ⎪ ⎪ ⎪ ⎪⎢⎥∂∂∂∂⎝⎭⎝⎭⎝⎭⎝⎭⎣⎦⎝⎭饱和蒸汽j j ii P P T T j j ii P P P P j j ii P P P j iP s dL L s dP c c T dT T P P dT v L v dP c c T T T T dT v L v L c c T T T v v ⎛⎫∂⎛⎫∂⎛⎫=+-+- ⎪ ⎪ ⎪∂∂⎝⎭⎝⎭⎝⎭⎛⎫∂⎛⎫∂⎛⎫=+--- ⎪ ⎪ ⎪∂∂⎝⎭⎝⎭⎝⎭⎛⎫∂⎛⎫∂⎛⎫=+--- ⎪ ⎪ ⎪∂∂-⎝⎭⎝⎭⎝⎭导出的方程可用在饱和蒸汽：现在应用这些方程来研究饱和蒸汽. 饱和蒸汽是指和凝聚相(液相或者固相)达到平衡的蒸汽. 设蒸汽相为相1,凝聚相为相2. 由于v 1≫v 2, 我们可以忽略上式中含v 2项的公式.()1211121,=P P P dL L v L c c dT T T v dP L LdT T v v Tv ∂⎛⎫≈+-- ⎪∂⎝⎭≈-如果把水蒸汽近试为理想气体1121211;P P P P P RT v Pv dL L L c c c c dT T T v =⇒∂⎛⎫=+--=- ⎪∂⎝⎭()012120;TP P P P T dL c c L c c dT L dT =-⇒=-+⎰对上式积分:如果蒸汽压变化不大, 并且加上凝聚相c p 2对压强依赖不大, 可以认为只是温度的函数:()012222TPPT c c dT L dP L LP dP L dT dTdT Tv RT P RTRT-+≈≈→≈=⎰（上步用了理想气体方程）()0012002ln .T TP P T T L dT P c c dT A RT RT ⇒=-+-+⎰⎰如果温度也变化不大,则c p 1,c p2可以看成常数,上式可以积分为 ln ln .BP A C T T=-+,,A B C可以实验测定,从而得到相变曲线超导相变对正常态和超导态(Meissner 态, 不考虑二类超导体 )的吉布斯函数满足下列方程,.N N N S S S dG s dT B dH dG s dT B dH =--=--在正常态和超导态 平衡线上有：();.N S N S c N SN SG G dG dG dH T s s dT B B =→=⇓-=--超导体排斥磁场， 故B s =0， 而且B N ≈0H c (T)。