Bianisotropic route to the realization and matching of backward-wave metamaterial slabs

a r X i v :c o n d -m a t /0607120v 3 [c o n d -m a t .o t h e r ] 10 A p r 2007

Bianisotropic route to the realization and matching of backward-wave metamaterial

slabs

S.A.Tretyakov,1C.R.Simovski,1,2M.Hudliˇc ka 1,3

1

Radio Laboratory/SMARAD,Helsinki University of Technology,P.O.Box 3000,FI-02015TKK,Finland

2

Physics Department,State University of Information Technologies,Mechanics and Optics,Sablinskaya 14,197101,St.Petersburg,Russia

3

Faculty of Electrical Engineering,Czech Technical University,Technick′a 2,16627,Prague 6,Czech Republic

(Dated:February 6,2008)

A concept of backward-wave bianisotropic composite medium matched to free space is suggested.It is based on the use of a uniaxial bianisotropic structure embedded into a matrix with negative e?ective permittivity.Since bianisotropy is easier to achieve in the optical range than arti?cial magnetism,this concept is prospective for optical backward-wave metamaterials.As an example of possible realizations,a microwave ?-composite combined with a wire lattice is analytically studied.

PACS numbers:78.20.Ci,42.70.Qs,42.25.Gy,73.20.Mf,78.67.Bf

Design and studies of materials with negative electro-magnetic parameters supporting backward waves is cur-rently a very active ?eld of research.The concept of back-ward waves is not new:It goes back to the beginning of

the 19th century and is connected to the names of Lamb,Schuster,and Pocklington.In the middle of the 20th cen-tury,this concept was extended to waves in homogeneous materials and negative refraction e?ect was theoretically predicted (Mandelshtam,Sivukhin,Silin,Veselago).De-tailed reviews on the current status and on the history of this research ?eld can be found in e.g.[1–7].

The main application for backward-wave materials is in sub-wavelength imaging devices (“perfect lens”[8]-[10]),but a full range of other possibilities is expected,especially for optical frequencies,if low-loss and matched slabs of backward-wave materials are realized [6,11].The well-known design approach for the microwave range is based on the use of arrays of long thin metal conductors and split rings [12].This approach has been extended to terahertz [13]and even infrared frequency range [14].Realization of negative permeability with the use of split rings becomes very problematic at optical frequencies,and some alternative approaches have been proposed [18]-[21].Considerable progress has been reported along this route,but the samples realized so far su?er from high losses and poor matching with free space [13,14].There exist possibilities to realize backward waves also in anisotropic media [15,16]and in anisotropic waveguides [17],which do not necessarily require magnetic proper-ties of materials,but are restricted to strongly anisotropic structures.In addition,di?culties to realize backward-wave samples matched to free space inhibit potential ap-plications both in the microwave and in the optical re-gions.

Majority of researchers focus on the design of magneto-dielectrics,where the backward-wave regime is realized when both the permittivity ?and permeability μhave negative real parts.Following to paper [22],the bian-isotropy is usually considered as a factor that one should

avoid in the design of backward-wave materials,and ef-fort is often concentrated on the design of symmetrical variants of split rings which minimizes magnetoelectric coupling [23].However,backward waves can exist in more general linear media,namely in bianisotropic media (e.g.,in chiral media [24]-[26]).It was recently demon-strated that in chiral media it is possible to improve the characteristics of backward-wave regime [26,27].More-over,as we will show in this paper,there is a possibility to bene?t from more design freedom o?ered by additional material parameters.Here we will show that it is possi-ble to design a bianisotropic material in such a way that it supports linearly-polarized backward waves and a slab made of this material is perfectly matched to free space for the normal direction of propagation.

The material can be realized as a composite with ?-shaped metal inclusions,and can be called omega-medium [28].Since reliable analytical models of ?-particles and ?-media were developed and checked nu-merically and experimentally for the microwave range [29–31],we use these models (valid below 70?100GHz)for a demonstration of the concept having in mind an optical realization as one of targets.

Reciprocal uniaxial ?-media obey the following consti-tutive relations [30]:

D =?·

E +j

√

ε0μ0KJ ·E

(1)

Denoting the unit vector along the optical axis as z 0we can write the permittivity and permeability dyadics in the form:

?=ε0 εt I t +εz z 0z 0 ,μ=μ0 μt I t +μz z 0z 0

,(2)where I t is the two-dimension unit dyadic de?ned in the plane orthogonal to z 0:I t =x 0x 0+y 0y 0.The magneto-electric dyadic is antisymmetric:J =z 0×I t .Complex dimensionless parameter K measures the magnetoelec-tric coupling e?ect.Eigenwaves in such media are lin-

2 early polarized plane waves,similarly to simple magneto-

dielectrics.

In this paper we consider a slab of such composite ma-

terial with the optical axis orthogonal to the slab sur-

face.For simplicity of the analysis we concentrate on the

normal-incidence excitation.In this case both eigenwaves

in the slab have the same propagation constant[30]

β=k0

εt

1?K2

√

ε0/μ0is the free-space wave admittance. In[32]it was shown that omega composites can be used to realize absorbing layers which are matched to free space.Indeed,one can notice that if the material parameters satisfy the condition

K=

j

2

(εt+μt).(6) This result shows that the magnetoelectric coupling not only allows one to match the slab to free space,but also makes it easier to realize the backward-wave regime. From formula(6)we see that the refractive index in a matched?-slab is negative when

Re{εt+μt}<0,(7) which is easier to satisfy than the usual conditions

Re{εt}<0,Re{μt}<0.(8) In particular,it is not necessary to realize negative per-meability,which can be more di?cult at the optical fre-quencies than to satisfy(5).Composites with negative permittivity and acceptable losses,on the contrary,are available in optics and can be obtained,for example,us-ing dilute arrays of metal nanoparticles embedded in a dielectric matrix.Like metal split rings[13,14,23],metal bianisotropic particles can possess a resonance in the in-frared range and,possibly,in the visible.Resonant mag-netoelectric coupling of these particles can be su?cient even if the corresponding resonant magnetic polarizabil-ity is not high.This expectation is based on the fact that the e?ect of arti?cial permeability is of the order ofμ～O(k0d)2,while the e?ect of magneto-electric cou-pling is an order of magnitude stronger:K～O(k0d). Here d is the characteristic particle

size.

FIG.1:Geometry of the matched backward-wave structure and of an individual particle.The uniaxial structure has a second identical set of particles lying in the x?z plane(not shown),however that second set does not interact with the eigenwave with the electric?eld polarized along y.D c is the ??lattice unit cell size,a w is the period of the wire lattice. To study if a realization is possible with a particular realistic dimensions we will next consider an example for the microwave frequency region.Negative permittivity at microwaves can be obtained using a lattice of parallel wires(e.g.,[33]).A uniaxial omega composite can be re-alized as a lattice of pairs of?-particles.One particle in the pair is orthogonal to the other[30,32].In this paper we restrict our study by the case of the normal propaga-tion direction.Then,for the simpli?ed structure shown in Fig.1all the formulas written above for a uniaxial composite are valid.Our purpose is to show that con-ditions(5)and(7)correspond to physically achievable geometric parameters of?-particles and wires forming the composite medium shown in Fig.1.

The microwave electromagnetic model of an omega particle represents the particle as a connection of a short wire dipole antenna and a small loop antenna[29].Small bianisotropic particles can be characterized by dyadic electric and magnetic polarizabilities,which de?ne the relations between induced electric and magnetic dipole

3 moments p,m and external electric and magnetic?elds

E,H applied to the particle[28]–[30]:

p=αee·E+αem·H(9)

m=αme·E+αmm·H(10)

For electrically small particles a lumped-element equiv-

alent circuit models of such antennas give acceptable ac-

curacy[30],and the particle polarizabilities can be ex-

pressed in terms of equivalent circuit parameters.If the

loop radius a of an?-particle shown in Fig.1is equal to

or larger than the arm length l,the polarizability com-

ponents relevant in the case of the normal propagation

can be approximated as

αyy ee=A

L0

,(11)

αxx mm=Bω2

L0

,(12)

αxy me=jωD

L0C0

,(13)

whereω0=1/

√

ωμ0

r0

,L0=μ0a log 8a

log(2l/r0)

,(15)

whereσis the metal conductivity,and dimensions r0, a and l are de?ned in Fig.1.Here we have neglected the electric polarization of the ring compared to that of the dipole portion which is an acceptable approxima-tion for electrically small?-particles[30].However,the bianisotropy of the particle described by formula(13)is practically that of the split ring loaded by a lumped ca-pacitance C0.This approximation is suitable for the case a≥l.

For the relative transversal permittivity and perme-ability and for the magnetoelectric coupling the low-density approximation(the particles concentration N is such that the unit cell of the composite is signi?cantly larger than the particles sizes)gives in accordance with [32]:

εt=εr+Nαyy ee

ε0(ω20?ω2+jωΓ),(16)

μt=μr+

Nαxx mm

μ0(ω20?ω2+jωΓ),(17)

K=Nj

αxy me

ε0μ0

=?N

ωD

ε0μ0

,(18)

whereεr andμr are the relative e?ective permittivity and

permeability of the background material,respectively.In

formulas(16)-(18)we use a di?erent notation for the

background material permittivity than in(15)because

in our structureεr=εm.The background permittiv-

ity is,of course,a?ected by the presence of metal wires

shown in Fig.1.However,the capacitance C0is deter-

mined by the quasi-stationary electric?eld in the small

spatial domain of the particle.That is why the matrix

permittivityεm and notεr enters C0(see more on this

important issue in[34]and[35]).

Conditions(5)and(7)should be satis?ed at the same

operational frequencyω.Substituting(16)-(18)into(5)

we come to equations for the real and imaginary parts of

(5):

2D

ε0μ0

=

(1?εr)

N

(ω20?ω2)= Aμ0 .(20)

Substituting(16)-(18)into(7)together with(19)and

(20)it is possible to show that conditionεr

hold for simultaneous validity of conditions(5)and(7).

This inequality can be satis?ed with the negative back-

ground permittivity created by the wire medium.If the

wave propagates in the plane orthogonal to the wires and

the electric?eld is oriented along them,the wire array

behaves as a low-frequency plasma.The permittivity of

the wire lattice is then not spatially dispersive,and we

have[33,36]

εr(ω)=εm 1?ω2p

ε0μ0a2w log a w

a2wε0μ0log a2w

4

(a)

(b)

(c)

(d)

FIG.2:Parameters of the bianisotropic layer with the de-signed lattice geometry.E?ective permittivity (a),perme-ability (b),normalized propagation factor β/k 0(c),re?ection and transmission coe?cients in dB for a 32-mm thick layer (d).

Let us pick up some reasonable values of parameters Γ,εm ,a,l,r 0(so that a >l and a,l ?r 0)and calculate ω0.Then from (19)and (20)we ?nd (1?εr )/N and ω.At the frequency ωthe medium under design is perfectly matched.Then varying N we satisfy the condition εr

σ=

ωμ0

ΓL 0r 0 2

.(24)The results for the particle parameters should satisfy to the following physical conditions:

?E?ective medium condition:D c <λe?/2,where λe?=2π/Re(β)is the e?ective wavelength in the medium at the working frequency and D c =N ?1/3is the size of a unit cell of the ?-lattice.

?Low concentration condition:D p =max(2a,2l )

?Metal conductivity:σshould be that of a known metal or alloy.

If any of these conditions are violated,one can vary the initial parameters Γ,εm ,a,l,r 0and ?nally ?nd their proper combination.Then we put the wire medium pe-riod be equal to the unit cell size a w =D c and ?nd the wire medium plasma frequency and the wire radius r w from formula (21)together with (22)or (23).These for-mulas allow us to study the frequency properties of the designed structure.

A result obtained for the following design parameters:εm =10,l =3.5mm,a =3.9mm,r 0=0.05mm,is pre-sented in Fig.2for the frequency band centered at the particle resonant frequency f 0=2.4393GHz.The per-fect matching holds at the frequency f =2.4359GHz.The parameter Γ=0.02·ω0corresponds to the con-ductivity σ≈1.6·1061/Ohm ·m.With small metal losses (those of copper)we could not satisfy the e?ective medium condition.Other parameters were found as ex-plained above:N =2.34·1051/m 3that corresponds to D c =a w ≈16.23mm and r w =0.07mm that allows the backward-wave condition over the particle resonance band.One can see that the permeability is positive in the backward-wave region.The backward-wave regime is due to the bianisotropy.The layer thickness was cho-sen d =2D c (the number of particles across the layer is enough to use the e?ective medium approximation).The thickness resonances happen at much higher frequencies than f (in the region where εr >0).

To conclude,a bianisotropic composite supporting backward waves can be obtained with physically real-izable parameters of inclusions.This makes the bian-isotropic route to matching a backward-wave composite be prospective for microwave and hopefully for optical metamaterials.Although this matching is perfect for the normal incidence only,the mismatch for oblique in-cidence should be of the same order as for conventional isotropic slabs with μ/?=μ0/?0.It is also important to notice that the omega slab matching is totally thickness independent and holds even for a semi-in?nite lattice.This work has been supported in part by the Grant Agency of the Czech Republic under project 102/06/1106”Metamaterials,nanostructures and their applications”and by the Finnish Academy via its Center-of-Excellence program.

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实验四：路由器基本配置

实验四：路由器基本配置 一、实验目的 学习命令行方式配置路由器的基本方法，理解路由器工作原理 二、实验内容 1.路由器配置方式 2.路由器基本配置命令 三、相关知识 路由器常用模式有： ①用户模式：提示符 >，登录路由器时进入该模式，在这个模式下只能查看部分交换机的信息，但不能修改信息。 ②特权模式：提示符 #，该模式是进入各种配置状态的入口，在这个模式下也只能查看路由器的信息，但不能修改。这个模式通常设置密码保护。 ③全局配置模式：提示符 (config)#，可以配置路由器的一些全局性信息，如名字、密码等。 ④接口配置模式：提示符 (config-if)#，可以配置路由器的接口信息。 ⑤路由配置模式：提示符 (config-router)#，可以在路由器上配置路由协议。 ⑥线路配置模式：提示符 (config-line)# ，可以配置路由器连接线路的参数。

conf t 命令是 configure terminal 命令的简写。 interface 命令中需要指明要配置的接口，如：interface e0 表示配置以太网接口e0，interface s0 表示配置串行口s0。 line 命令中需指明要配置的登录线路，如：line console 0 表示配置控制台端口0，line vty 0 4 表示配置远程登录端口0~4。 router 命令中需指明配置的协议类型，如：router rip 表示配置RIP协议。 exit 命令用于退回到上一层模式。Ctrl+Z或end用于从深层模式直接退回特权模式。 logout 命令用于注销，结束会话。 四、实验内容 1、配置路由器名字 路由器的名字用于识别各路由器，默认名为Router。假如把路由器的名字改为R1，可用以下命令： Router(config)#hostname R1 R1(config)# 配置后，路由器的名字会出现在命令提示符前面。 2、设置控制台口令

独立主格with用法小全

独立主格篇 独立主格，首先它是一个“格”，而不是一个“句子”。在英语中任何一个句子都要有主谓结构，而在这个结构中，没有真正的主语和谓语动词，但又在逻辑上构成主谓或主表关系。独立主格结构主要用于描绘性文字中，其作用相当于一个状语从句，常用来表示时间、原因、条件、行为方式或伴随情况等。除名词/代词+名词、形容词、副词、非谓语动词及介词短语外，另有with或without短语可做独立主格，其中with可省略而without不可以。*注：独立主格结构一般放在句首，表示原因时还可放在句末；表伴随状况或补充说明时，相当于一个并列句，通常放于句末。 一、独立主格结构： 1. 名词/代词+形容词 He sat in the front row, his mouth half open. Close to the bank I saw deep pools, the water blue like the sky. 靠近岸时，我看见几汪深池塘，池水碧似蓝天。 2. 名词/代词+现在分词 Winter coming, it gets colder and colder. The rain having stopped, he went out for a walk.

The question having been settled, we wound up the meeting. 也可以The question settled, we wound up the meeting. 但含义稍有差异。前者强调了动作的先后。 We redoubled our efforts, each man working like two. 我们加倍努力，一个人干两个人的活。 3. 名词/代词+过去分词 The job finished, we went home. More time given, we should have done the job much better. *当表人体部位的词做逻辑主语时，不及物动词用现在分词，及物动词用过去分词。 He lay there, his teeth set, his hands clenched, his eyes looking straight up. 他躺在那儿，牙关紧闭，双拳紧握，两眼直视上方。 4. 名词/代词+不定式 We shall assemble at ten forty-five, the procession to start moving at precisely eleven. We divided the work, he to clean the windows and I to sweep the floor.

struggle的用法和短语例句

struggle的用法和短语例句 【篇一】struggle的用法 struggle的用法1：struggle的基本意思是“奋斗”,即为实现某一目的而尽力做某事。常指遇到有力的反抗而在逆境中拼搏或努力从 束缚中解脱出来。有时含有“挣扎”的意味。 struggle的用法2：struggle也可表示“(与某人)争斗,搏斗,打斗”,还可表示“艰难地(朝某方向)行进”。 struggle的用法3：struggle是不及物动词,与介词against连用,表示“同与之对立或对抗的人或物实行斗争”; 与介词for连用,表示“为…而斗争”。 struggle的用法4：struggle可接动词不定式作目的状语。 struggle的用法5：struggle的基本意思是“斗争”,表示抽象的行为,用作不可数名词; 表示具体的“打斗,搏斗,战斗,斗争”时,可用作可数名词。 struggle的用法6：struggle作“努力,奋斗”解时,一般用单数形式。 【篇二】struggle的常用短语 struggle against (v.+prep.) struggle along1 (v.+adv.) struggle along2 (v.+prep.) struggle for (v.+prep.) struggle in (v.+prep.) struggle on (v.+adv.)

struggle out (v.+adv.) struggle with (v.+prep.) 【篇三】struggle的用法例句 1. It's a constant struggle to try to keep them up to par. 要让他们达标，需要持续努力。 2. Curiously, the struggle to survive has greatly improved her health. 奇怪的是，她拼命求生的抗争使得她的健康状况大有好转。 3. He grandly declared that "international politics is a struggle for power". 他一本正经地宣称“国际政治是一场权力之争”。 4. This age-old struggle for control had led to untold bloody wars. 这场由来已久的对控制权的争夺已经引发了无数流血的战争。 5. It is only a hobby, not a life or death struggle. 这仅仅一项爱好，不需要拼死拼活地努力。 6. There is a ceaseless struggle from noon to night. 从中午到夜晚，争斗没有停歇。 7. He is currently locked in a power struggle with his Prime Minister. 他当前陷入了一场同的权力之争当中。 8. He praised her role in the struggle against apartheid.

(完整版)助动词用法及练习

be动词，情态动词，助动词do/does的用法区别及练习 助动词，顾名思义就是帮助动词完成疑问及否定的，本身没有什么含义。主要的助动词有be,do,will,have等，其用法详述如下： 一、⑴由连系动词am，is，are构成的句子：变一般疑问句时把am，is，are提到句子的前面，句尾用问号即可。变否定句时直接在am，is，are后面加not即可。例如： 肯定句:He is a student. 一般疑问句: Is he a student? 否定句: He is not a student. 画线提问: 对he提问: Who is a student? 对a student 提问: What is he? (2)was 是am,is的过去式，were是are的过去式，若句子中有以上两词时，变疑问句及否定句方法与（1）相同。 二、(1) 由情态动词can, may,will ，shall等构成的句子: 变一般疑问句时把can, may,will ，shall提到句子的前面,句尾用问号即可.变否定句时直接在can,may,后面加not即可. 例如: 肯定句: She can swim. 一般疑问句: Can she swim? 否定句: She can not swim. 画线提问: 对she提问: Who can swim? 对swim提问: What can she do? （2）could,might,would,should是can,may,will,shall的过去式，若句子中有以上两词时，变疑问句及否定句方法与（1）相同。 三、（1）由行为动词构成的句子: 需要加助词do或does. 变一般疑问句时把do/does放在句子前面. 变否定句时把don’t/doesn’t放在动词的前面。要注意观察动词的形式并对号入座。一般疑问句和否定句的动词三单式都要变回原型。 play-----do plays-----does 例如: 肯定句: They play football after school. He plays football after school. 一般疑问句: Do they play football after school? Does he play football after school? 否定句: They don't (do not) play football after school. He doesn’t’ play football after school. 画线提问: 对they/he提问: Who plays football after school? 对play football提问: What do they do after school? What does he do after school? 对after school提问: When do they play football? When does he play football? （2）did是do和did的过去式，变一般疑问句时把did放在句子前面. 变否定句时把didn’t 放在动词的前面, 要注意观察动词的形式并对号入座。一般疑问句和否定句的动词都要变回原型。

实验四、路由器基本配置

实验四路由器基本配置 一、实验目的 1.熟悉路由器开机界面； 2.掌握H3C路由器几种常用配置方法； 3.掌握H3C路由器基本配置命令。 二、实验环境 H3C路由器、标准Console配置线、双绞线、PC。 三、实验内容 1．预备知识 （1）MSR2600-30路由器规格说明 1:电源适配器插座2:电源开关3:千兆以太网接口GE 4:千兆以太网接口GE15:串行配置口CON/AUX6:USB配置口CON 7:USB接口 图A-2MSR26-30后视图

1:SIC接口模块32:SIC接口模块2 3:SIC接口模块14:接地端子 （2）H3C26-30结构 硬件组成： CPU(处理器） RAM(存储正在运行的配置文件、报文缓存) FLASH（负责保存OS的映像和路由器的微码） NVRAM（非易失，相当于硬盘，保存配置件） ROM（加载OS） 接口（完成路由器与其它设备的数据交换）

软件结构： BOOT ROM：主要功能是路由器加电后完成有关初始化工作，并向内存中加入操作系统代码。 COMWARE：华为路由器上运行的软件平台。 2.通过console口配置路由器 （1）搭建环境（类似配置交换机） （2）运行超级终端并设置通讯参数； （3）与路由器连接（按Enter键，将进入路由器视图）

3．路由器的各种视图 视图分类：用户视图、系统视图、路由协议视图、接口视图、用户界面视图。 路由器常用命令视图功能特性列表 视图名称功能提示符进入命令退出命令 系统视图配置系统参数[H3C]用户登录后即进入logout断开与路由器连接 RIP视图配置RIP协议参数[H3C-rip]在系统视图下键入rip quit返回系统视图 同步串口视图配置同步串口参数[H3C-Serial0] 在任意视图下键入 interface serial0 quit返回系统视图 异步串口视图配置异步串口参数[H3C-Async0] 在任意视图下键入 interface async0 quit返回系统视图 AUX接口 视图配置AUX接口参数[H3C-Aux0] 在任意视图下键入 interface aux0 quit返回系统视图 以太网接口 视图配置以太网口参数[H3C-Ethernet0] 在任意视图下键入 interface ethernet0 quit返回系统视图 ACL视图配置访问控制列表规则[H3C-acl-1]在系统视图下键入 acl1 quit返回系统视图 说明： (1)命令行提示符以网络设备名（缺省为H3C）加上各种命令视图名来表示，如“[H3C-rip]”。 (2)各命令根据视图划分，一般情况下，在某一视图下只能执行该视图限定的命令；但对于一些常用的命令，在所有视图下均可执行，这些命令包括：ping、display、debugging、reset、save、interface、logic-channel、controller。 (3)上表中有些视图需要首先启动相应功能，才能进入；有些视图需要首先配置相关限制条件，才能进入。 (4)在所有视图中，使用quit命令返回上一级视图，使用return命令直接返回系统视图。 4．系统的基本配置与管理 （1）路由器的名称配置（在系统视图下） 操作命令 配置路由器的名称sysname sysname

5种基本句型和独立主格结构讲解

英语中的五种基本句型结构 一、句型1：Subject (主语) ＋Verb (谓语) 这种句型中的动词大多是不及物动词，所谓不及物动词，就是这种动词后不可以直接接宾语。常见的动词如：work, sing, swim, fish, jump, arrive, come, die, disappear, cry, happen等。如： 1) Li Ming works very hard.李明学习很努力。 2) The accident happened yesterday afternoon.事故是昨天下午发生的。 3）Spring is coming. 4) We have lived in the city for ten years. 二、句型2：Subject (主语) ＋Link. V(系动词) ＋Predicate(表语) 这种句型主要用来表示主语的特点、身份等。其系动词一般可分为下列两类： (1)表示状态。这样的词有：be, look, seem, smell, taste, sound, keep等。如： 1) This kind of food tastes delicious.这种食物吃起来很可口。 2) He looked worried just now.刚才他看上去有些焦急。 (2)表示变化。这类系动词有：become, turn, get, grow, go等。如： 1) Spring comes. It is getting warmer and warmer.春天到了，天气变得越来越暖和。 2) The tree has grown much taller than before.这棵树比以前长得高多了。 三、句型3：Subject(主语) ＋V erb (谓语) ＋Object (宾语) 这种句型中的动词一般为及物动词, 所谓及物动词，就是这种动词后可以直接接宾语，其宾语通常由名词、代词、动词不定式、动名词或从句等来充当。例： 1) He took his bag and left.（名词）他拿着书包离开了。 2) Li Lei always helps me when I have difficulties. (代词)当我遇到困难时，李雷总能给我帮助。 3) She plans to travel in the coming May Day.（不定式）她打算在即将到来的“五一”外出旅游。 4) I don’t know what I should do next. (从句)我不知道下一步该干什么。 注意：英语中的许多动词既是及物动词，又是不及物动词。 四、句型4：Subject(主语)＋Verb(谓语)＋Indirect object(间接宾语)＋Direct object (直接宾语) 这种句型中，直接宾语为主要宾语，表示动作是对谁做的或为谁做的，在句中不可或缺，常常由表示“物”的名词来充当；间接宾语也被称之为第二宾语，去掉之后，对整个句子的影响不大，多由指“人”的名词或代词承担。引导这类双宾语的常见动词有：buy, pass, lend, give, tell, teach, show, bring, send等。如： 1) Her father bought her a dictionary as a birthday present.她爸爸给她买了一本词典作为生日礼物。 2）The old man always tells the children stories about the heroes in the Long March. 老人经常给孩子们讲述长征途中那些英雄的故事。上述句子还可以表达为： 1）Her father bought a dictionary for her as a birthday present. 2）The old man always tells stories about the heroes to the children in the Long March. 五、句型5：Subject(主语)＋Verb (动词)＋Object (宾语)＋Complement(补语) 这种句型中的“宾语＋补语”统称为“复合宾语”。宾语补足语的主要作用或者是补充、说明宾语的特点、身份等；或者表示让宾语去完成的动作等。担任补语的常常是名词、形容词、副词、介词短语、分词、动词不定式等。如： 1）You should keep the room clean and tidy. 你应该让屋子保持干净整洁。（形容词） 2) We made him our monitor.(名词)我们选他当班长。 3) His father told him not to play in the street.(不定式)他父亲告诉他不要在街上玩。

高中英语单词天天记struggle素材

· struggle · v. ['str?gl] ( struggles; struggled; struggling ) · · 双解释义 · vi.斗争,奋斗,努力fight; try to overcome difficulties, etc.; make great efforts · 基本要点 ? 1.struggle的基本意思是“奋斗”,即为实现某一目的而尽力做某事。常指遇到有 力的反抗而在逆境中拼搏或努力从束缚中解脱出来。有时含有“挣扎”的意味。 2.struggle也可表示“(与某人)争斗,搏斗,打斗”,还可表示“艰难地(朝某方向) 行进”。 3.struggle是不及物动词,与介词against连用,表示“同与之对立或对抗的人或物 进行斗争”; 与介词for连用,表示“为…而斗争”。 4.struggle可接动词不定式作目的状语。 ? · 词汇搭配 ? ?struggle bravely 勇敢地斗争 ?struggle desperately 拼命地斗争,绝望地挣扎 ?struggle furiously 激烈地搏斗 ?struggle successfully 成功地作斗争 ?struggle wildly 疯狂地挣扎 ?struggle on 勉强支持下去,竭力维持下去 ? ?struggle against 与…作斗争

?struggle against difficulties 同困难斗争 ?struggle against tyranny 与暴政作斗争 ?struggle for 为…而斗争 ?struggle for a living 为生计而挣扎 ?struggle for freedom 为自由而斗争 ?struggle for independence 为独立而奋斗 ?struggle for recognition 为获得承认而奋斗 ?struggle in sb's arms (小孩)在母亲怀里挣扎 ?struggle through the snowstorm 冒着暴风雪行进 ?struggle to one's feet 挣扎着站起来 ?struggle with 与…作斗争 ? · 常用短语 ? struggle against(v.+prep.) 为反对…而斗争 oppose sth with difficulty ▲struggle against sb/sth He struggled against those who opposed his plan.他与那些反对他计划的人进 行了斗争。 In Chinese history the peasants kept struggling against the rule of the feudal class.在中国历史上,农民不断地与封建阶级的统治作斗争。 What is the use of trying to struggle against the system?力图反对这种制度有什么用? The swimmer struggled against the tide.游泳者逆流而上。 We must struggle against this prejudice for a more tolerant attitude to our beliefs.我们必须反对这种偏见,以争得对我们的信仰采取更为宽容的态度。 The workers have been struggling against bad conditions for too long.很久以来,工人们就在为反对恶劣的工作条件而进行斗争。

助动词的用法

助动词在英语学习当中作了解，不需要重点把握，但是助动词也是很好理解的，希望回答能够帮到你。 1.助动词：Be 助动词不能作述语动词,要与本动词一起构成动词片语,表示时态、语态等。 1. BE作为本动词表示状态或客观存在等意思。 Your house is bigger and nicer than mine. 你的房子比我的又大又好。 2. BE+不定词连用,表示约定、义务、命令等未来的动作或状态。 I am to go abroad on business tomorrow. 明天我要去外国出公差。 表示未来的安排。 The meeting is to be held as scheduled. 会议将按原计划召开。 表示计划好的安排。 You are not to bark at my friend. 你不许对我的朋友叫。 表示命令或要求。 3. BE+现在分词构成各种进行时态。 Who are you talking to? 你在和谁说话？ I am talking to my dog. 我在和我的狗说话。 4. BE+过去分词构成被动语态。 That means I will be promoted as scheduled. 这就意味着我将要按原计划得到提升。 2. dare和used to 作为情态助动词的dare一般只能用于疑问句或否定句中,dare+原形动词表示敢。

I dare not say it is ugly. 我不敢说它丑。 How dare you say so? 你怎么敢这么说？ dare也可以作本动词,用于肯定句,后面要接带to的不定词;主词若是第三人称单数,简单现在式时,dare要变为dares。 You, you dare to talk to me like this! 你、你竟敢这样和我讲话！ used to+原形动词表示过去的习惯或状态,而现在已经不存在了。 You're not what you used to be. 你不是以前的你了。 used to构成疑问句时有两种形式。即used + 主词+ to + 其他成份？；Did + 主词+ use to+ 其他成份。 How used I to be? 我以前什么样？ How did you use to be? 你以前什么样？ used to构成否定句时有两种形式，即used not to和didn't use to。 You didn't use to say things like this. You used not to say things like this. 你以前不会说这样的话的。 be used to表示习惯于,其中used是形容词,to是介系词,后接名词、代名词或动名词等,可用于不同的时态。 You're used to hearing words of praise. 你是听好话听惯了。 3. 助动词：Do 1. DO作为助动词时的时态、人称和数的变化与它作为本动词相同,有do, does, did三种形式。 Yes, it seems he doesn't really want to have a haircut.

路由器实验报告1

路由器技术实验报告 ------------安徽工业大学计算机与科学技术学院

《路由器技术》实验指导书 一．实验总学时（课外学时/课内学时）：22 开实验个数： 7 二．适用专业：计算机专业 三．考核方式及办法：在规定实验时间内完成实验要求,依据实验过程、实验结果和实验报告综合考核。四．配套的实验教材或指导书：自编实验指导书 五. 实验项目： 实验一：Packet Tracer软件使用交换机的配置与管理 （内容一）：认识 Packet Tracer软件 Packet Tracher介绍 Packet Tracer 是 Cisco 公司针对CCNA认证开发的一个用来设计、配置和故障排除网络的模拟软件。Packer Tracer 模拟器软件比 Boson 功能强大，比 Dynamips 操作简单，非常适合网络设备初学者使用。学习任务： 1、安装 Packer Tracer； 2、利用一台型号为 2960 的交换机将 2pc机互连组建一个小型局域网； 3、分别设置pc机的ip 地址； 4、验证 pc 机间可以互通。 实验设备： Switch_2960 1 台；PC 2 台；直连线 配置信息： PC1 IP： Submask： Gateway： PC2 IP： Submask：：

（内容二）：交换机的基本配置与管理 1.实验目标： 掌握交换机基本信息的配置管理。 2.实验背景： 某公司新进一批交换机，在投入网络以后要进行初始配置与管理，你作为网络管理员，对交换机进行基本的配置与管理。 3.技术原理： 交换机的管理方式基本分为两种：带内管理和带外管理。 1.通过交换机的 Console 端口管理交换机属于带外管理；这种管理方式不占用交换机的网络端口，第一次配置交换机必须利用 Console端口进行配置。 2.通过Telnet、拨号等方式属于带内管理。 交换机的命令行操作模式主要包括： 用户模式 Switch> 特权模式 Switch# 全局配置模式 Switch(config)# 端口模式 Switch(config-if)# 4.实验步骤： 新建Packet Tracer 拓扑图 了解交换机命令行 进入特权模式(en) 进入全局配置模式(conf t) 进入交换机端口视图模式(int f0/1) 返回到上级模式(exit) 从全局以下模式返回到特权模式(end) 帮助信息(如、co、copy)

(完整版)独立主格结构用法全解

独立主格结构 独立主格结构（Absolute Structure）是由名词或代词加上分词等构成的一种独立结构，用于修饰整个句子。独立主格结构中的名词或代词与其后的分词等构成逻辑上的主谓关系。这种结构与主句不发生句法上的联系，它的位置相当灵活，可置于主句前、主句末或主句中，常由逗号将其与主句分开。需特别注意的是，独立主格结构与主句之间不能使用任何连接词。 二、独立主格结构基本构成形式 名词(代词)+现在分词（过去分词；形容词；副词；不定式；名词；介词短语） 1. 名词(代词)+现在分词 Night enshrouding the earth, nobody could make out what the dark mass was from a distance． 黑夜笼罩大地，谁也看不清远处黑压压的一片是什么东西。 There being no bus, we had to walk home. 由于没有公共汽车，我们只好走回家。 2. 名词(代词)+过去分词 The workers worked still harder, their living conditions greatly improved. 由于工人们的生活条件大大提高，他们工作得更起劲了。 He was listening attentively in class, his eyes fixed on the blackboard. 他上课专心听讲，眼睛紧盯着黑板。 3. 名词(代词)+不定式 在“名词/代词+动词不定式”结构中，动词不定式和它前面的名词或代词如果存在着逻辑上的主谓关系，动词不定式则用主动的形式；如果是动宾关系，则用被动形式。 The four of us agreed on a division of labor, each to translate a quarter of the book. 我们四人同意分工干，每人翻译全书的四分之一。 Many trees, flowers, and grass to be planted, our newly-built school will look even more beautiful. 种上许多的树、花和草后，我们新建的学校看上去将更美。 4. 名词(代词)+形容词 Computers very small, we can use them widely. 电脑虽小，我们却能广泛地利用它们。 5. 名词(代词)+副词 The meeting over, our headmaster soon left the meeting room. 散会了，校长很快就离开了会议室。 The lights off, we could not go on with the work. 灯熄了，我们不能继续工作了。 6. 名词(代词)+名词 His first shot failure，he fired again． 他第一枪没击中，又打了一枪。 Two hundred people died in the accident, many of them children. 两百人死于事故，其中有许多儿童。 7. 名词(代词) +介词短语

不定式用法详解

不定式用法详解 定义：在句子中充当除了谓语以外的各种句子成分的动词形式叫做非谓语动词。 非谓语动词有三种：不定式，动名词，分词。 注：非谓语动词具有时态和语态的变化，可以同否定词not连用，构成否定形式，可以带宾语，状语，补语。非谓语动词的名词，形容词，副词的特征；可用在句中做主语，宾语，补语，状语，和定语等。 —不定式（原形动词前加to, 构成动词不定式。不定式不做谓语，属于非谓语动词） 不定式的时态，语态 一般式：不定式所表示的动作和谓语动词所表示的动作或状态同时发生或几乎同时发生或存在。但多数情况下是在谓语动词所表示的动作之后发生。 e.g :They often watch us play football. (同时) She hopes to go there again. (之后发生) 完成式：不定式所表示的动作或状态发生在谓语动词所表示动作或状态之前。 e.g : I’m glad to have seen your mother yesterday 注：1）用在intended, expected, meant, hoped. promised, wanted, planned. wished. thought, desired, was, were等后，表示过去没有实现的愿望，期待或计划的等，也用来表示先于谓语动词发生的动作或状态。 e.g: He wanted to have met (=had wanted to meet) you at the airport,but he didn’t get there in time. 他原想去机场接你（事情已经发生），但他没及时赶到那儿。（没接成） e.g: We planned to have done (had planned to do) good deeds for the poor people last month. 我们原计划上个月为贫困的人们作些好事。（没作成）。

助动词的用法

助动词 协助主要动词构成谓语动词词组的词叫助动词（Auxiliary Verb）。被协助的动词称作主要动词（Main Verb）。构成时态和语态。助动词是语法功能词，自身没有词义，不可单独使用，它没有对应的汉译，例如：He doesn't like English. 他不喜欢英语。（does是助动词，无词义；like是主要动词，有词义) 最常用的助动词有：be, have, do, shall, will, should, would 他们表示时态，语态，构成疑问句与否定副词not合用，加强语气助动词半助动词 2 半助动词 功能介绍 在功能上介乎主动词和助动词之间的一类结构，称为半助动词。常见的半助动词有be about to, be due to, be going to, be likely to, be meant to, be obliged to, be supposed to, be willing to, have to, seem to, be unable to, be unwilling to等。......情态助动词 情态助动词1.情态助动词包括will(would), shall(should), can(could), may(might), must, need, dare, ought to, used to, had better后接原形不定词。2.情态助动词不受主语的人称和数的限制。3.两个情态助动词不能连用。中文:他将能够及时完成此事。(误)He will can finish it i...... 3 基本助动词 基本助动词基本助动词只有三个：be, do, have, 他们没有词汇意义，只有语法作用，如协助构成进行体，完成体，被动态，否定句，疑问句等。例如He is giving a lecture. 他在作报告He has made a plan. 他已经订了计划The small animals are kept in the cages. 小动物都关在笼子里。 助动词协助主要动词完成以下功用 a. 表示时态，例如： He is singing. 他在唱歌。 He has got married. 他已结婚。 b. 表示语态，例如： He was sent to England. 他被派往英国。 c. 构成疑问句，例如： Do you like college life? 你喜欢大学生活吗？ Did you study English before you came here? 你来这儿之前学过英语吗？ d. 与否定副词not合用，构成否定句，例如： I don't like him. 我不喜欢他。 e. 加强语气，例如： Do come to the party tomorrow evening. 明天晚上一定来参加晚会。 He did know that. 他的确知道那件事。 3）最常用的助动词有：be, have, do, shall, will, should, would 4 具体用法 have的用法 一、have作助动词 形式 主要变化形式：have，has，had 动名词/现在分词：having 1）have +过去分词，构成完成时态，例： He has left for London.他已去了伦敦。

路由器基本配置_实验报告

路由器基本配置_实验报告 《组网技术》实验报告 姓名学号教学班计算机网络 任课教师王丽娟指导教师王丽娟班主任 2013-6-3 实验地点广西某家具公司机房实验时间 实验项目名称:路由器基本配置 实验目标及要求: 通过CISCO路由器,了解路由器的各个接口的用途、配接方法，路由器配置命令、状态模式的功能，在此基础上通过超级终端完成对路由器的各种基本配置，如:路由器的命名、特权密码的设置、LAN接口的配置、WAN接口的配置、静态路由的配置等等。并用命令保存和查验配置信息。 实验环境及工具: CISCO路由器，PC机，网线，专用电缆(RS232，V35)，CONSOLE。 实验内容及过程: 实验内容: 观察CISCO路由器，了解路由器基本知识; 学习电缆连接; 查看CISCO路由器的操作，了解路由器工作原理; 学习基本的路由器配置。 实验步骤: 配置相应的IP参数 打开计算机的“超级终端”程序 此超级终端内输入的命令都是对路由器A的操作，超级终端窗口内所有输出都是路由器A的 输出。 键入“,”列入命令提示。 7-A>? Exec commands: <1-99> Session number to resume access-enable Create a temporary Access-List entry access-profile Apply user-profile to interface clear Reset functions connect Open a terminal connection disable Turn off privileged commands disconnect Disconnect an existing network connection

独立主格用法详解

一、 独立主格结构是一个名词或代词（作为逻辑主语），加上一个形容词、副词、介词短语、分词、不定式等在句中作状语。它有以下三个特点： (1)结构的逻辑主语与句子的主语不同，它独立存在。 (2)名词或代词与后面的形容词、副词、介词短语、分词、不定式等存在逻辑上的主谓关系。 (3)独立主格结构一般用逗号与主句分开，但与主句之间不能使用任何连接词。 二、 英语中，的形式是：名词或代词跟形容词、副词、介词短语、非谓语动词连在一起，构成。 1.名词/ 代词+ 不定式。如： A house to be built, we must save every cent. 由于要建一座房子，我们必须节省每一分钱。 Now here is Li Lei, Wei Fang to come tomorrow. 现在李蕾来了，魏方明天到。 2.名词/ 代词+ -ing分词。如： The bus coming here soon, we should get everything ready. 汽车很快就要来了，我们应该把一切事情准备好。 Mother being ill, Li Lei was very worried. 母亲病了，李蕾非常焦急。 3.名词/ 代词+ 动词的过去分词。如： His cup broken, he used his bowl instead. 茶杯破了，他就用碗来代替。 4.名词/ 代词+ 形容词。如： The ground muddy, we should be careful. 地面泞泥，我们应该小心。 5.名词/ 代词+ 副词。如： The class over, we all went out to play. 下课后，我们都出去玩。 6. Glasses in his hand, he asked where his glasses were. 手里拿着眼镜，他问他的眼镜哪去了。 三、 在句子中作状语，表示时间、原因、条件和伴随等情况。 1.作时间状语 School over, the students went home. 放学后，学生们都回家了。 The ceremony ended, the games began. 仪式结束后，比赛开始了。 2.作条件状语 It being fine tomorrow, we’ll go boating. 如果明天天气好的话，我们就去划船。

初中英语10大词类详解+用法+考点(总结详细篇)

2020年初中英语10大词类详解+用法+考点(总结详细篇) 一、词性得分类 词类又叫词性，英语单词凭据其在句子中得功用，可以分红十个大年夜类。 1.名词 noun n. student 学生 2.代词 pronoun pron. you 你 3.形容词 adjective adj. happy 雀跃得 4.副词 adverb adv. quickly 敏捷地 5.动词 verb v. cut 砍、割 6.数词 numeral num. three 三 7.冠词 article art. a 一个 8.介词 preposition prep. at 在... 9.连词 conjunction conj. and 和 10.慨叹词 interjection interj. oh 哦 前六类叫实词，后四类叫虚词。 二、名词 名词单数得规则改变

名词得格 在英语中有些名词可以加“‘s”来示意所有关系，带这种词尾得名词形式称为该名词得所有格，如：a teacher’s book。 名词所有格得规则如下： (1)单数名词词尾加“'s”，单数名词词尾没有s，也要加“'s”，如the boy‘s bag 男孩得书包，men’s room 男厕所。 (2)若名词已有单数词尾-s ，只加“'”，如：the workers’ struggle工人得斗争。 三、代词 大年夜少数代词具有名词和形容词得功用。 英语中得代词，按其意义、特征及在句中得作用分为：人称代词、物主代词、指导代词、反身代词、彼此代词、疑问代词、关系代词、毗邻代词和不定代词九种。 人称代词得用法：

指导代词 指导代词分单数（this / that）和单数（these / those）两种形式，既可作限制词又可做代词。 疑问代词 指人：who， whom， whose 指物：what 既可指人又可指物：which 四、冠词 冠词是位于名词或名词词组之前或以后，在句子里首如果对名词起限制作用得词。冠词是一种虚词。 不定冠词a (an)与数词one 同源，是“一个”得意思。 定冠词得用法 定冠词the与指导代词this，that同源，有“那（这）个”得意思。 (1)特指双方都熟悉打听得人或物：Take the medicine.把药吃了。 (2)上文提到过得人或事：He bought a house. I’ve been to the house. (3)指世上独一物二得事物：the sun， the sky， the moon， the earth（敲黑板，这个是常常会在选择题中考到得常识点） (4)单数名词连用示意一类事物，如：the dollar 美元；the fox 狐狸；