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Momentum-Transfer to and Elementary-Excitations of a Bose-Einstein Condensate by a Time-Dep

Momentum-Transfer to and Elementary-Excitations of a Bose-Einstein Condensate by a Time-Dep
Momentum-Transfer to and Elementary-Excitations of a Bose-Einstein Condensate by a Time-Dep

a r X i v :c o n d -m a t /0207749v 1 [c o n d -m a t .s o f t ] 31 J u l 2002

Momentum-Transfer to and Elementary-Excitations of a Bose-Einstein Condensate by

a Time-Dependent Optical Potential

Y.B.Band and M.Sokuler

Departments of Chemistry and Physics,Ben-Gurion University of the Negev,Beer-Sheva,Israel 84105We present results of calculations on Bose-Einstein condensed 87Rb atoms subjected to a moving standing-wave light-potential of the form V L (z,t )=V 0(t )cos(qz ?ωt ).We calculate the mean-?eld dynamics (the order paramter)of the condensate and determine the resulting condensate momen-tum in the z direction,P z (q,ω,V 0,t p ),where V 0is the peak optical potential strength and t p is the pulse duration.Although the local density approximation for the Bogoliubov excitation spectral distribution is a good approximation for very low optical intensities,long pulse duration and suf-?ciently large values of the wavevector q of the light-potential,for small q ,short duration pulses,or for not-so-low intensities,the local density perturbative description of the excitation spectrum breaks down badly,as shown by our results.

I.INTRODUCTION

Elementary excitations of a Bose-Einstein condensate (BEC)can be explored with matter-wave interference studies using two-photon Bragg pulse spectroscopy [1–10].In such studies,the momentum imparted to the BEC by a Raman scattering process can be studied as a function of the temporal duration of the optical pulses,t p ,the detuning of the Bragg pulses from atomic resonance,?,the intensity of the Bragg pulses,the di?erence of the Bragg pulse wavevectors which is denoted by the wavevector q ,and the di?erence of the central frequency of the two laser pulses ω.In the linear response limit,the response of the BEC to a weak perturbation with wavevector q and energy ˉh ωis given in terms of the dynamic structure factor S (q ,ω)[11],

S (q ,ω)=

1

2

z 2+

mω2x,y

intensities for the two Bragg pulses.When the Bragg pulses are switched on,the atoms are trapped at the antinodes of a vertically oriented,red-detuned optical moving standing-wave;the antinodes are separated by ?z =λ/(2sin(θ/2)).The momentum transferred to an atom upon absorbing a photon from the ?eld with wavevector k 1and emitting a photon with wavevector k 2is given by ˉh q =ˉh (k 1?k 2)=ˉh q ?z ,where the ˉh q =2ˉh k ph sin(θ/2),and ˉh k ph =2πˉh /λis the photon momentum.Here λ=780nm is the central wavelength of the Bragg pulses.The light-potential experienced by the atoms in the BEC as a result of the Bragg pulses is given by V L (z,t )=V 0(t )cos(qz ?ωt ).The well-depth of the optical potential,V 0(t ),is proportional to the intensity of the Bragg pulses and inversely proportional to the detuning

from resonance,?,i.e.,V 0(t )=ˉh

?1(t )?2(t )

?t

=(

p 2

m

is the atom-atom nonlinear interaction strength which is proportional to the s -wave

scattering length a 0and the total number of condensed atoms N .The wave function (order parameter)ψ(r ,t )is propagated with a split-operator fast Fourier transform method.Due to the large number of grid points necessary in the lattice direction (z ),we found it necessary to convert the 3D GPE into an e?ective 1D GPE with similar dynamics as described in Ref.[17].The wave function in momentum space,ψ(k z ,t ),is determined by taking the Fourier transform of ψ(z,t ).The net momentum of the BEC at any time t is given by

P z (t )= ∞

?∞

dk z ψ?(k z ,t )(ˉh k z )ψ(k z ,t ).(4)

The expectation values of all dynamical quantities (e.g.,energies, ?z ,etc.)can be easily determined using the

calculated wavepackets in either position or momentum space.

A perturbative estimate of the rate of momentum-transfer to the BEC by the Bragg pulses is given by [18]

dP z (t )

ˉ

h q V 0?(q )[?(q )+2gn ],

(6)

where ?(q )=(ˉh q )2/2m ,n is the density,and the dynamic structure factor is given by S (q ,ω)=

?(q )

2ˉh

t

dt ′V 20(t ′)

q?(q )?(q )[?(q )+2gn ]

δ(ˉh ω?E B (q )).(7)

Thus,the momentum transferred by a moving standing-wave excitation to a uniform condensate is non-vanishing

only when ω=?B (q ),and its magnitude is proportional to the product of the integral over time of V 20and q?(q )

For a non-uniform BEC with density pro?le that varies smoothly with position,one can de?ne a local Bogoliubov excitation energy,

E B(q,r)≡ˉh?B(q,r)=

δ(ˉhω?E B(q,r)).(9)

E B(q,r)

Hence,in perturbation theory(i.e.,small V0),the momentum transferred to the non-uniform condensate can be approximated by substituting S LDA(q,ω)for S(q,ω)on the right hand side of Eq.(5).Thus,momentum transfer of a non-uniform condensate via a moving standing-wave excitation is smeared over a range of frequencies around ω=?B(q),and its magnitude is determined by carrying out an average of q?(q)

ˉh mωz)and pulse duration t p=6ms.The calculations were performed for three di?erent laser intensities corresponding to potential well depths V0=0.0054,0.0162and0.054E R.The low intensity curve peaks near the Bogoliubov frequency?B(q)=8657s?1.This peak has a tail at lowerωwhich is due to the non-uniform density of the BEC;E B(q,r)for positions away from the center of the BEC is smaller than at the center and this can give rise to the tail,as can be understood from Eqs.(9)and(5).At intermediate and high V0,a power broadening of the spectral distribution P z(ω)is evident in Fig.1;at these values of V0,higher order (nonlinear)processes that populate±2q momenta take place(see Fig.2).These phenomena can not be understood from a perturbative treatment.At even higher values of V0,the spectral distribution becomes even wider and the peak structure becomes even more complicated and ragged.

Fig.2shows|ψ(k z,t)|2vs.k z for the low intensity case appearing in Fig.1forω=8945and9597s?1.The

net positive momentum,(P z(ω)>0)resulting at these frequencies in Fig.1is due to the fact that the peak at √

k z=q(≈0.390ˉh k ph=80

ˉh mωz;the origin of this feature is not clearly understood.The peaks at k z=±2q are almost two orders of magnitude reduced compared with the k z=±q peaks.As the intensity of the lasers(the potential well depths)increase,the size of the k z=±2q peaks grow in comparison with the k z=±q peaks, and|ψ(k z,t)|2grows at intermediate values of k z between the peaks at k z=±jq,where j is a positive integer. Fig.3is similar to Fig.1,except the pulse duration was taken to be1ms.The width of the distribution P z(ω)as a function ofωfor t p=1ms is considerably wider than for t p=6ms for the low and intermediate intensities.The shorter temporal duration and therefore larger bandwidth of the1ms Bragg pulses allows for a wider distribution in frequency of P z(ω)versusω.The width hides the tail of the distribution at lowerωdue to the non-uniform BEC density.For the high intensity case,the distribution does not change very much from the low and intermediate cases. Moreover,it is narrower than the high intensity6ms result shown in Fig.1because the pulse?uence is smaller,hence higher order processes do not signi?cantly broaden the distribution.However,for the ultrahigh intensity case,power broadening of the distribution is signi?cant.Note that the perturbation theory expression(5)can not account for the time-domain broadening shown in Fig.3(since it is derived assuming that the spectral width of V0is within that of S(q,ω)).Eq.(5)shoud be modi?ed to account for the bandwidth of the optical pulse:

dP z(t)

q 12π dωe?iωt|V0(ω)|2S(q,ω)+c.c. .(10)

2ˉh

This equation should then be integrated over time to obtain an expression that replaces(7)for P z(t).

We now consider smaller values of momentum-transfer q such that the excitation wavelengths of the optical potential

are comparable or larger than the size of the condensate.Fig.4shows P z versusωforθ=10o(q=0.174ˉh k ph=√

35.8

higher order nonlinear processes.Upon reducing the optical potential by a factor of0.3from the low intensity case

to V0=0.00162E R(the curve labeled ultralow),new features in the spectrum become clear.The small feature near ω=860s?1and the tail of the Bogoliubov peak at2411s?1,which was presumably due to an inhomogeneous density e?ect,become two ancillary peaks.The reason for the structure in the spectrum for the ultralow(and low)intensity

can be understood by looking at|ψ(k z,t)|2vs.k z for this case as shown in Fig.5.Peaks at k z=q=35.8

ˉh mωz),t p=6ms and potential well depths V0=0.00162,0.0054,0.0162and0.054E R.At ultralow,low and intermediate intensities,an additional peak appears atω≈400s?1.At all but ultralow intensity,the main peak in the spectrum is near the Bogoliubov frequency ?B(q)=2061s?1.At ultralow intensity the peak atω≈400s?1is even larger than that atω≈2000s?1and P z between these peaks becomes negative.Again,interference e?ects arising for reasons explained in connection with Fig.5are apparently responsible.A complicated interference pattern appears around the values of k z=±q in |ψ(k z,t)|2vs.k z(?gure not shown).This interference plays a role in the determination of the spectrum shown in Fig.6.The peaks in|ψ(k z)|2at k z=q forω=370and1687s?1are larger than the peak at k z=q forω=990s?1, and therefore maxima occur in the distribution shown in Fig.6atω=370and1687s?1and a minimum between

the peaks in the spectrum occurs forω=990s?1.

Fig.7shows P z versusωforθ=3o(q=5.24×10?2ˉh k ph=11

Foundation(grant No.98-421),Jerusalem,Israel,the Israel Science Foundation(grant No.212/01)and the Israel MOD Research and Technology Unit.

0.001

0.010.1110

-200

-150

-100-50050100150200

89459597

k (harmonic oscillator momentum units)|ψ(k )|2z

z FIG.2.|ψ(k z ,t )|2vs.k z for the low intensity case appearing in Fig.1at ω=8945and 9597s ?1

.The units of k z are in harmonic oscillator momentum units

ω (s )

-1M o m e n t u m (h a r m o n i c o s c i l l a t o r u n i t s )

FIG.4.Same as Fig.1except for 10o (q =0.174ˉh k ph ).Results for three laser intensities corresponding to potential well depths V 0=0.00162,0.0054and 0.054E R are shown.The arrow indicates the position of ?B (q ).

0.001

0.010.1110

-40

-30

-20-1001020

30

40

860

3807

k (harmonic oscillator momentum units)|ψ(k )|2

z

z FIG.5.|ψ(k z ,t )|2vs.k z ,for the ultralow intensity case shown in Fig.4at ω=860and 3807s ?1.The units of k z are in harmonic oscillator momentum units

ω (s )

-1M o m e n t u m (h a r m o n i c o s c i l l a t o r u n i t s )

FIG.6.Same as Fig.

1except for 5o (q =8.72×10?2ˉh k ph ).Results for four di?erent laser intensities corresponding to

potential well depths V 0=0.00162,0.00540.0162and 0.054E R are shown.The arrow indicates position of ?B (q ).

M o m e n t u m (h a r m o n i c o s c i l l a t o r u n i t s )

ω (s )

-1FIG.7.Same as Fig.1except for 3o (q =5.24×10?2ˉh k ph ).Results for four di?erent laser intensities corresponding to

potential well depths V 0=0.00162,0.0054,0.0162and 0.054E R are shown.The arrow indicates position of ?B (q ).

8

最新The_Monster课文翻译

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(工艺技术)电镀工艺基础知识

2、电镀新工艺介绍 2 .1合金电镀 合金电镀一直是电镀新工艺开发的重要领域。以往为取代昴贵的镀镍而开发的铜锡合金,就曾经是一种新工艺。现在的代镍和节镍镀层,也都是各种合金。因为合金可以综合单一金属的优点,并具有单一金属所不具备的新的特性,比如硬度、耐腐蚀性、功能性等。现在已经认识到,电镀作为一种湿法冶金技术,能生产出用电、热方法做不到的新合金。包括在制作非晶态材料和纳米材料方面,电镀技术都是有优势的。合金电镀的原理在传统的理论中是要求两种共沉积的金属的电极电位要接近,如果一个的电位较正,另一个的电位较负,就要采用络合剂将正电位的金属的离子络合,使之放电电位向负的方向移动,与另一金属的电位相近,达到共沉积的目的。这在现在也仍然对合金新工艺的开发有指导意义。但是现在越来越多的合金中的另一种成分的量非常小,就是这种少量的金属分散在另一金属中,却改变了金属的性能。用传统冶金学的观点是这些掺入的金属是占据在主体金属的某些晶格位上,从而改变了金属的物理性能。但实际上,用火法冶金很难把微量金属分散到另一金属中去,而采用电镀的方法则比较容易做到。不过电镀方法得到的合金的结构是否符合冶金学的原理,则是值得探讨的课题。现在已经得到应用的新合金工艺有锌系列,镍系列,铜系列,锡系列,银系列等。锌作为钢铁的优良廉价的防护性镀层被广泛地采用 , 但是自从日本汽车打进欧洲和北美市场,汽车的耐盐防护性就提到了议事日程。〈1〉在开展高耐蚀性镀层的研究中,锌合金的研究引人注目。最先出现的是锡锌合金,这种合金的含锌量在30%左右时耐盐水喷雾时间最长,出现红锈的时间可达1500个小时以上。最开始进入实用化的工艺是70年代末的有机羧酸的中性镀液,后来有柠檬酸镀液,现在我公司已经开发出硫酸盐光亮镀锡锌工艺。在锡锌工艺之后出现的是锌镍工艺。这种工艺由于含镍量在5-10%,成本比锡锌要低,因此很快得到普及。最先出现的是用于钢板连续电镀的硫酸盐工艺,这大约在1982年前后。以后开发出氯化铵型工艺,现在比较成熟的是碱性锌酸盐工艺。这种工艺的特点是抗腐蚀性能特别好,不经钝化的镀层耐盐雾到出现红锈的时间在150小时以上。在高温下也仍能维持其优良的防护性能。因此在汽车等行业有较多应用。 在锌镍开发之后两年,锌铁工艺就进入了实用化。锌铁与前面的工艺不同的是铁的含量很小,只在 0.2 到0.6 左右。虽然以前有用于钢板电镀的锌铁合金,其含铁量在10-20%,但现在进入实用的还是这种低铁含量的镀层。比较成熟的有锌酸盐工艺。其耐蚀性也很好,但一定要经过钝化才能有高的耐蚀性,当含铁量在 0. 4 左右时,出现红锈的盐水喷雾时间可达1500小时以上。现在,我公司已经开发出氯化钠型锌铁新工艺,并有黄色、彩色等高耐蚀性的钝化产品。 在欧洲还有用锌钴合金工艺的,这种工艺与锌铁一样,可以不用银盐做出黑色钝化膜。含钴量也仅在1%左右. 镍一直是电镀加工工业中的重要镀种,由于镍资源的紧张和价格昂贵,开发镍合金电镀是节镍的一种选择。同时,有些镍合金的功能性能也是市场所需要的,因此,镍基合金的应用也很广泛。镍铁合金不仅可节约部分镍,而且镀层性能也比纯镍镀层要好。这种镀层的含铁量在 7%-30% 左右,镀层中的含铁量与镀液中的镍铁比例成正比。也有采用镍锰铁合金电镀工艺的报导。 <2 >用于装饰的镍合金更多,特别是黑色镀层方面,不少是用的镍合金,比如镍锡,镍钴,镍镉等。铜镍合金更是在装饰电镀中有较多的应用。 <3 >铜合金如铜锡合金,铜锌合金,很早就有大量的应用。这方面的新工艺的主攻方向是以非氰化物络合物来取代氰化物,比如焦磷酸盐,柠檬酸盐镀铜合金等。锡作为钎焊性镀层主要是用在电子电镀行业,但也可以用在装饰和防护方面,比如代银的锡合金,用于罐头盒防腐的镀锡工艺等。但主要还是电子工业中有大量应用,现在用得最多的仍然是锡铅合金。也有锡铈,锡铋等。当前的趋势是采用无氟和无铅的新工艺取代老工艺。<4 >其它贵金属的合金主要是用在装饰和功能性方面,这里就不一一加以介绍。正如前面讲到的,由于合金电镀技术的开发可能产生出一些新的合金,这不仅在表面处理业有重要意义,对材料学科也有重要意义。因此,在新世纪,对合金电镀的研究仍会加紧进行。 特别是在多元合金,包括三元、四元合金等的开发上还有很大的空间 2.2电子电镀 如前所述,21世纪被称为高信息化世纪。所谓高信息化世纪就是以因特网为传播工具的信息爆炸的世纪。在这个世纪内,电子产品的品种和产量将有更快更大的发展,这给电子电镀业也带来很大的机遇和挑战。因此,现在新工艺的开发有很大的比重将放在电子电镀方面。 所谓电子电镀就是用于电子产品或电子工业的电镀技术。用于电子行业的镀层有很多,包括导电性镀层,钎焊性镀层,信息载体镀层,电磁屏蔽镀层,电子功能性镀层,印刷电路板电镀,电子构件防护性镀层,电子产品装饰性镀层等。电子电镀工艺除了少数是利用了传统的工艺以外,大多数是近几十年开发的新工艺。比如非金属电镀新工艺,化学镀新工艺,贵金属电镀新工艺,合金电镀新工艺等。 以印刷线路板的电镀为例,它是以孔金属化为中心的综合了前处理、化学镀、电镀、退镀等技术的工艺。印

新版人教版高中语文课本的目录。

必修一阅读鉴赏第一单元1.*沁园春?长沙……………………………………毛泽东3 2.诗两首雨巷…………………………………………戴望舒6 再别康桥………………………………………徐志摩8 3.大堰河--我的保姆………………………………艾青10 第二单元4.烛之武退秦师………………………………….《左传》16 5.荆轲刺秦王………………………………….《战国策》18 6.*鸿门宴……………………………………..司马迁22 第三单元7.记念刘和珍君……………………………………鲁迅27 8.小狗包弟……………………………………….巴金32 9.*记梁任公先生的一次演讲…………………………梁实秋36 第四单元10.短新闻两篇别了,“不列颠尼亚”…………………………周婷杨兴39 奥斯维辛没有什么新闻…………………………罗森塔尔41 11.包身工………………………………………..夏衍44 12.*飞向太空的航程……………………….贾永曹智白瑞雪52 必修二阅读鉴赏第一单元1.荷塘月色…………………………………..朱自清2.故都的秋…………………………………..郁达夫3.*囚绿记…………………………………..陆蠡第二单元4.《诗经》两首氓采薇5.离骚………………………………………屈原6.*《孔雀东南飞》(并序) 7.*诗三首涉江采芙蓉《古诗十九首》短歌行……………………………………曹操归园田居(其一)…………………………..陶渊明第三单元8.兰亭集序……………………………………王羲之9.赤壁赋……………………………………..苏轼10.*游褒禅山记………………………………王安石第四单元11.就任北京大学校长之演说……………………..蔡元培12.我有一个梦想………………………………马丁?路德?金1 3.*在马克思墓前的讲话…………………………恩格斯第三册阅读鉴赏第一单元1.林黛玉进贾府………………………………….曹雪芹2.祝福………………………………………..鲁迅3. *老人与海…………………………………….海明威第二单元4.蜀道难……………………………………….李白5.杜甫诗三首秋兴八首(其一) 咏怀古迹(其三) 登高6.琵琶行(并序)………………………………..白居易7.*李商隐诗两首锦瑟马嵬(其二) 第三单元8.寡人之于国也…………………………………《孟子》9.劝学……………………………………….《荀子》10.*过秦论…………………………………….贾谊11.*师说………………………………………韩愈第四单元12.动物游戏之谜………………………………..周立明13.宇宙的边疆………………………………….卡尔?萨根14.*凤蝶外传……………………………………董纯才15.*一名物理学家的教育历程……………………….加来道雄第四册阅读鉴赏第一单元1.窦娥冤………………………………………..关汉卿2.雷雨………………………………………….曹禹3.*哈姆莱特……………………………………莎士比亚第二单元4.柳永词两首望海潮(东南形胜) 雨霖铃(寒蝉凄切) 5.苏轼词两首念奴娇?赤壁怀古定风波(莫听穿林打叶声) 6.辛弃疾词两首水龙吟?登建康赏心亭永遇乐?京口北固亭怀古7.*李清照词两首醉花阴(薄雾浓云愁永昼) 声声慢(寻寻觅觅) 第三单元8.拿来主义……………………………………….鲁迅9.父母与孩子之间的爱……………………………..弗罗姆10.*短文三篇热爱生

todo与doing的区别

--- to do与doing的区另U 一般情况下,to do 是一般将来式,是打算去做什么(未做);doing是现在进行式,是现在正在做什么,或(此事已做过或已发生、正做) like to do 和like doing 的用法有什么区别 简单的记忆方法。当表示喜欢,用like doing ,如:He likes cooking in his house. She likes singing. 表示爱好。 当表示想要,欲做某事(但还没进行)用like to do ,例如:He likes to cook in his house.- 他想在自己家做饭吃。 She likes to stay with us.- 她想和我们带一块儿。(但还没进行) 2 forget doin g/to do forget to do 忘记要去做某事。(未做) forget doing 忘记做过某事。(已做) The light in the office is stil on. He forgot to turn it off. 办公室的灯还在亮着,它忘记关了。(没有做关灯的动作) He forgot turning the light off. 他忘记他已经关了灯了。(已做过关灯的动作) Don't forget to come tomorrow. 别忘了明天来。(to come动作未做) 3 remember doin g/to do remember to do 记得去做某事(未做) remember doing 记得做过某事(已做) Remember to go to the post office after school. 记着放学后去趟邮局。 Don't you remember see ing the man before? 你不记得以前见过那个人吗? 感官动词 see, watch, observe, notice, look at, hear, listen to, smell, taste, feel +doing表示动作的连续性,进行性 I saw him working in the garden yesterday. (强调”我见他正干活”这个动作) 昨天我见他正在花园里干活。

电镀工艺技术规范

精心整理1?目的本规范规定了零部件电镀层的选择和各镀种及化学处理的标注方法。?本规范适用于产品零部件设计时电镀层种类的选择。? 2?引用标准?GB1238-76?JB/288-75? 3?电镀层的主要目的? 3.1?保护金属零件表面,防止腐蚀。? 3.2?装饰零件外表,使外表美观。? 3.3?提高零件的工作性能。如提高表面硬度、耐磨性、导电性、导磁性、耐热性、钎焊性、反光能力;节约及代替有色金属或贵金属;提高轴承使用寿命;修复磨损零件;热处理时的局部保护以及其它特殊性能。? 4?决定电镀层种类和厚度的因素 4.1零件的工作环境; 4.2被镀零件的种类、材料和性质;? 4.3电镀层的性质和用途;? 4.4零件的结构、形状和尺寸的公差;? 4.5镀层与其互相接触金属的材料、性质;? 4.6零件的要求使用期限。? 5?镀层使用条件的分类? 5.1腐蚀性比较严重的工作环境:大气中含有较多的工业气体、燃料废气、灰尘和盐分以及相对湿度较大的地区。例如工业城市、离海较近的地区和湿热带地区等。或具有大量燃料废气和二氧化硫的室内,以及经常接触手汗的工作条件。? 5.2腐蚀性中等的工作环境:大气中含有少量的工业气体、燃料废气、灰尘和盐分以及相对湿度中等的地区。例如离海较远的一般城市和一般室内环境。?

5.3?腐蚀性轻微的工作环境:大气中工业气体、燃料废气、灰尘和盐分的含量很少,而且气候比较干燥。例如干热带地区、密封良好的设备的内部。? 从防腐蚀的要求来看,有些金属在腐蚀性轻微的条件下可以不加保护层而应用。在比较严重的工作环境下,大部分金属要求有一定形式的防护,而有些金属则不能使用。? 从保护基体金属免受腐蚀的要求来看,一般可考虑:? a.贵金属(金、铂)、含铬18%以上的不锈钢、轧制的磁性合金材料、以及镍铜合金等,一般不需再加防护层。? b.碳钢、低合金钢和铸铁制造的零件,在大气中容易腐蚀,应加保护层。由于工作条件的限制不能采用保护层时,应采用油封防锈。在油中工作的零件,可以不加防护层。? c.铜和铜合金制造的零件,根据不同的使用条件,采用光亮酸洗、钝化、电镀或涂漆保护等。用磷青铜或铍青铜制造的精密零件可以不进行表面处理。? d.铝和铝合金制造的零件,可以采用阳极氧化和封闭处理。不适于阳极氧化的小零件,可采用化学氧化处理。铸造铝合金可采用涂漆防护。用作通信机箱的铝合金须进行导电氧化。? e.锌合金制造的零件,可以采用磷化、钝化、电镀或涂漆防护。? 6?电镀层的选择? 6.1?各类电镀层的特性及用途?镀层按其用途可分下列三类:? a.防护性镀层:主要作用是保护基体金属免受外界腐蚀,不规定对产品的装饰要求。? b.防护-装饰性镀层:除保护基体金属外,还使零件表面美观。?

高中外研社英语选修六Module5课文Frankenstein's Monster

Frankenstein's Monster Part 1 The story of Frankenstein Frankenstein is a young scientist/ from Geneva, in Switzerland. While studying at university, he discovers the secret of how to give life/ to lifeless matter. Using bones from dead bodies, he creates a creature/ that resembles a human being/ and gives it life. The creature, which is unusually large/ and strong, is extremely ugly, and terrifies all those/ who see it. However, the monster, who has learnt to speak, is intelligent/ and has human emotions. Lonely and unhappy, he begins to hate his creator, Frankenstein. When Frankenstein refuses to create a wife/ for him, the monster murders Frankenstein's brother, his best friend Clerval, and finally, Frankenstein's wife Elizabeth. The scientist chases the creature/ to the Arctic/ in order to destroy him, but he dies there. At the end of the story, the monster disappears into the ice/ and snow/ to end his own life. Part 2 Extract from Frankenstein It was on a cold November night/ that I saw my creation/ for the first time. Feeling very anxious, I prepared the equipment/ that would give life/ to the thing/ that lay at my feet. It was already one/ in the morning/ and the rain/ fell against the window. My candle was almost burnt out when, by its tiny light,I saw the yellow eye of the creature open. It breathed hard, and moved its arms and legs. How can I describe my emotions/ when I saw this happen? How can I describe the monster who I had worked/ so hard/ to create? I had tried to make him beautiful. Beautiful! He was the ugliest thing/ I had ever seen! You could see the veins/ beneath his yellow skin. His hair was black/ and his teeth were white. But these things contrasted horribly with his yellow eyes, his wrinkled yellow skin and black lips. I had worked/ for nearly two years/ with one aim only, to give life to a lifeless body. For this/ I had not slept, I had destroyed my health. I had wanted it more than anything/ in the world. But now/ I had finished, the beauty of the dream vanished, and horror and disgust/ filled my heart. Now/ my only thoughts were, "I wish I had not created this creature, I wish I was on the other side of the world, I wish I could disappear!” When he turned to look at me, I felt unable to stay in the same room as him. I rushed out, and /for a long time/ I walked up and down my bedroom. At last/ I threw myself on the bed/ in my clothes, trying to find a few moments of sleep. But although I slept, I had terrible dreams. I dreamt I saw my fiancée/ walking in the streets of our town. She looked well/ and happy/ but as I kissed her lips,they became pale, as if she were dead. Her face changed and I thought/ I held the body of my dead mother/ in my arms. I woke, shaking with fear. At that same moment,I saw the creature/ that I had created. He was standing/by my bed/ and watching me. His

电镀工艺

电镀工艺目录

阳极泥 展开 复制搜索 编辑本段概述 电镀是指在含有欲镀金属的盐类溶液中,以被镀基体金属为阴极,通过电解作用,使镀液中欲镀金属的阳离子在基体金属表面沉积出来,形成镀层的一种表面加工方法。镀层性能不同于基体金属,具有新的特征。根据镀层的功能分为防护性镀层,装饰性镀层及其它功能性镀层。 电镀基本原理图 编辑本段电镀的基本原理 电镀是一种电化学过程,也是一种氧化还原过程.电镀的基本过程是将零件浸在金属盐的溶液中作为阴极,金属板作为阳极,接直流电源后,在零件上沉积出所需的镀层。 例如:镀镍时,阴极为待镀零件,阳极为纯镍板,在阴阳极分别发生如下反应: 阴极(镀件):Ni2++2e→Ni (主反应) 2H++e→H2↑ (副反应) 阳极(镍板):Ni -2e→Ni2+ (主反应) 4OH--4e→2H2O+O2+4e (副反应) 不是所有的金属离子都能从水溶液中沉积出来,如果阴极上氢离子还原为氢的副反应占主要地位,则金属离子难以在阴极上析出.根据实验,金属离子自水溶液中电沉积的可能性,可从元素周期表中得到一定的规律,如表1.1所示。 阳极分为可溶性阳极和不溶性阳极,大多数阳极为与镀层相对应的可溶性阳极,如:镀锌为锌阳极,镀银为银阳极,镀锡-铅合金使用锡-铅合金阳极.但是少数电镀由于阳极溶解困难,使用不溶性阳极,如酸性镀金使用的是多为铂或钛阳极.镀液主盐离子靠添加配制好的标准含金溶液来补充.镀铬阳极使用纯铅,铅-锡合金,铅-锑合金等不溶性阳极。 编辑本段工艺过程 一般包括电镀前预处理,电镀及镀后处理三个阶段。完整过程: 1、浸酸→全板电镀 五金及装饰性电镀工艺程序

人教版高中语文必修必背课文精编WORD版

人教版高中语文必修必背课文精编W O R D版 IBM system office room 【A0816H-A0912AAAHH-GX8Q8-GNTHHJ8】

必修1 沁园春·长沙(全文)毛泽东 独立寒秋, 湘江北去, 橘子洲头。 看万山红遍, 层林尽染, 漫江碧透, 百舸争流。 鹰击长空, 鱼翔浅底, 万类霜天竞自由。 怅寥廓, 问苍茫大地, 谁主沉浮。 携来百侣曾游, 忆往昔峥嵘岁月稠。

恰同学少年, 风华正茂, 书生意气, 挥斥方遒。 指点江山, 激扬文字, 粪土当年万户侯。 曾记否, 到中流击水, 浪遏飞舟。 雨巷(全文)戴望舒撑着油纸伞,独自 彷徨在悠长、悠长 又寂寥的雨巷, 我希望逢着 一个丁香一样地

结着愁怨的姑娘。 她是有 丁香一样的颜色, 丁香一样的芬芳, 丁香一样的忧愁, 在雨中哀怨, 哀怨又彷徨; 她彷徨在这寂寥的雨巷,撑着油纸伞 像我一样, 像我一样地 默默彳亍着 冷漠、凄清,又惆怅。她默默地走近, 走近,又投出 太息一般的眼光

她飘过 像梦一般地, 像梦一般地凄婉迷茫。像梦中飘过 一枝丁香地, 我身旁飘过这个女郎;她默默地远了,远了,到了颓圮的篱墙, 走尽这雨巷。 在雨的哀曲里, 消了她的颜色, 散了她的芬芳, 消散了,甚至她的 太息般的眼光 丁香般的惆怅。 撑着油纸伞,独自

彷徨在悠长、悠长 又寂寥的雨巷, 我希望飘过 一个丁香一样地 结着愁怨的姑娘。 再别康桥(全文)徐志摩 轻轻的我走了,正如我轻轻的来; 我轻轻的招手,作别西天的云彩。 那河畔的金柳,是夕阳中的新娘; 波光里的艳影,在我的心头荡漾。 软泥上的青荇,油油的在水底招摇; 在康河的柔波里,我甘心做一条水草! 那榆荫下的一潭,不是清泉, 是天上虹揉碎在浮藻间,沉淀着彩虹似的梦。寻梦?撑一支长篙,向青草更青处漫溯, 满载一船星辉,在星辉斑斓里放歌。

todoanddoing用法

加to do 的动词 attempt企图enable能 够 neglect忽视afford负担得 起 demand要求long渴 望 arrange安排destine注 定 mean意欲,打算begin开 始 expect期望omit忽略,漏 appear似乎,显得determine决定manage设 法cease停止 hate憎恨,厌恶pretend假装 ask问dread害 怕 need需要agree同 意

desire愿望love 爱 swear宣誓volunteer志愿 wish希望bear承 受 endeavor努力offer提 供 beg请求fail不 能 plan计划 bother扰乱;烦恼forget忘 记 prefer喜欢,宁愿care关心,喜欢happen碰 巧prepare准 备decide决 定learn学 习 regret抱歉,遗憾choose选择hesitate犹 豫profess表明

claim要求hope希 望 promise承诺,允许start开始undertake承 接want想要 consent同意,赞同intend想要refuse拒 绝decide决定 learn学习vow起contrive设法,图谋incline有…倾向propose提议seek 找,寻觅 try试图 2)下面的动词要求不定式做宾补:动词+宾语+动词不定式 ask要求,邀请get请,得 到 prompt促使allow允 许 forbid禁止prefer喜欢,宁愿announce宣 布force强

迫 press迫使bride 收 买 inspire鼓舞request请求 assist协助hate憎 恶 pronounce断定,表示advise 劝告exhort告诫,勉 励pray请求 authorize授权,委托help帮 助recommend劝告,推荐bear容 忍implore恳 求remind提醒 beg请求induce引 诱 report报告compel强 迫 invite吸引,邀请,summon传 唤command命 令intend想要,企

(完整版)Unit7TheMonster课文翻译综合教程四

Unit 7 The Monster Deems Taylor 1He was an undersized little man, with a head too big for his body ― a sickly little man. His nerves were bad. He had skin trouble. It was agony for him to wear anything next to his skin coarser than silk. And he had delusions of grandeur. 2He was a monster of conceit. Never for one minute did he look at the world or at people, except in relation to himself. He believed himself to be one of the greatest dramatists in the world, one of the greatest thinkers, and one of the greatest composers. To hear him talk, he was Shakespeare, and Beethoven, and Plato, rolled into one. He was one of the most exhausting conversationalists that ever lived. Sometimes he was brilliant; sometimes he was maddeningly tiresome. But whether he was being brilliant or dull, he had one sole topic of conversation: himself. What he thought and what he did. 3He had a mania for being in the right. The slightest hint of disagreement, from anyone, on the most trivial point, was enough to set him off on a harangue that might last for hours, in which he proved himself right in so many ways, and with such exhausting volubility, that in the end his hearer, stunned and deafened, would agree with him, for the sake of peace. 4It never occurred to him that he and his doing were not of the most intense and fascinating interest to anyone with whom he came in contact. He had theories about almost any subject under the sun, including vegetarianism, the drama, politics, and music; and in support of these theories he wrote pamphlets, letters, books ... thousands upon thousands of words, hundreds and hundreds of pages. He not only wrote these things, and published them ― usually at somebody else’s expense ― but he would sit and read them aloud, for hours, to his friends, and his family. 5He had the emotional stability of a six-year-old child. When he felt out of sorts, he would rave and stamp, or sink into suicidal gloom and talk darkly of going to the East to end his days as a Buddhist monk. Ten minutes later, when something pleased him he would rush out of doors and run around the garden, or jump up and down off the sofa, or stand on his head. He could be grief-stricken over the death of a pet dog, and could be callous and heartless to a degree that would have made a Roman emperor shudder. 6He was almost innocent of any sense of responsibility. He was convinced that

电镀工艺

电镀工艺 一、目的: 电镀的目的是在底层铜上加厚镀铜(图形电镀将在加厚镀铜之后再镀上一层抗蚀镀层Sn,以保护所需铜在蚀板时不被蚀去,形成所需图形)。 二、流程简介: 1.板面电镀: PTH—→上/下板—→预浸—→镀铜—→水洗—→下板—→焜棍—→水 洗—→上板。 2.图形电镀: 前工序(D/F)—→上/下板—→除油—→双水洗—→微蚀—→水洗—→预 浸—→镀铜—→喷水洗—→预浸—→镀锡—→双水洗—→下板—→焜棍—→水洗—→上板。 三、流程的功能: 1.除油: 作用:①清洁铜面,除去包括手指印,显影后残留的有机和无机污染物等。 ②润湿铜面,特别是孔壁。 控制参数:H2SO4:4~6% V/V 温度:35±5℃ 除油剂SE–250 22~28% V/V 影响:除油剂浓度太低或温度太低可能会导致甩铜、孔内无铜及线路凹痕等缺陷。 2.水洗: 作用:清洁、去除生产板上除油剂等杂污,避免带入下一流程而造成污染,影响品质。 影响:水流量太小,水质差会有较多的线路凹痕产生。水流量要求>2000L/hr。

3.微蚀: 作用:①粗化待镀底层铜表面,以增大其表面积而增大结合力。 ②进一步清洁板面与孔壁铜层。 控制参数:过硫酸钠(NPS):40~60g/l H2SO4:1~3% Cu2+:<15g/l 温度:30±2℃ 影响:NPS浓度太低或温度太低会引起甩铜缺陷,NPS浓度太高或微蚀时间过长会导致孔内无铜。 基本要求:①打气②过滤③冷却 4.水洗: 作用:将微蚀后生产板上残留的药水洗去以避免带入下一流程而造成污染。 5.预浸缸: 作用:①将微蚀后底层铜产生的Cu氧化物蚀去,保证镀铜前底层铜面清洁。 ②保护酸铜缸,使液中H2SO4浓度维持相对稳定。 控制参数:H2SO4:8~12% V/V 影响:H2SO4浓度太低会导致板面粗糙。 6.铜缸: ①基本要求: a. 打气 b. 循环过滤 c. 冷却 d. 摇摆 ②镀铜原理: 阳极Cu–2e—→Cu2+ 阴极Cu2++2e—→Cu↓ ③操作条件: A.电流密度: 对一般的生产而言,阴极的电流密度应为1.0~3.5A/dm2(9.3~ 32.6A/ft2),在低电位会有比较好的厚度分布和整平作用,但对 于添加剂中的Brightener会造成较大的用量,而高电位的情况则 相反。

人教版高中语文必修一背诵篇目

高中语文必修一背诵篇目 1、《沁园春长沙》毛泽东 独立寒秋,湘江北去,橘子洲头。 看万山红遍,层林尽染;漫江碧透,百舸争流。 鹰击长空,鱼翔浅底,万类霜天竞自由。 怅寥廓,问苍茫大地,谁主沉浮? 携来百侣曾游,忆往昔峥嵘岁月稠。 恰同学少年,风华正茂;书生意气,挥斥方遒。 指点江山,激扬文字,粪土当年万户侯。 曾记否,到中流击水,浪遏飞舟? 2、《诗两首》 (1)、《雨巷》戴望舒 撑着油纸伞,独自 /彷徨在悠长、悠长/又寂寥的雨巷, 我希望逢着 /一个丁香一样的 /结着愁怨的姑娘。 她是有 /丁香一样的颜色,/丁香一样的芬芳, /丁香一样的忧愁, 在雨中哀怨, /哀怨又彷徨; /她彷徨在这寂寥的雨巷, 撑着油纸伞 /像我一样, /像我一样地 /默默彳亍着 冷漠、凄清,又惆怅。 /她静默地走近/走近,又投出 太息一般的眼光,/她飘过 /像梦一般地, /像梦一般地凄婉迷茫。 像梦中飘过 /一枝丁香的, /我身旁飘过这女郎; 她静默地远了,远了,/到了颓圮的篱墙, /走尽这雨巷。 在雨的哀曲里, /消了她的颜色, /散了她的芬芳, /消散了,甚至她的 太息般的眼光, /丁香般的惆怅/撑着油纸伞,独自 /彷徨在悠长,悠长 又寂寥的雨巷, /我希望飘过 /一个丁香一样的 /结着愁怨的姑娘。 (2)、《再别康桥》徐志摩 轻轻的我走了, /正如我轻轻的来; /我轻轻的招手, /作别西天的云彩。 那河畔的金柳, /是夕阳中的新娘; /波光里的艳影, /在我的心头荡漾。 软泥上的青荇, /油油的在水底招摇; /在康河的柔波里, /我甘心做一条水草!那榆阴下的一潭, /不是清泉,是天上虹 /揉碎在浮藻间, /沉淀着彩虹似的梦。寻梦?撑一支长篙, /向青草更青处漫溯, /满载一船星辉, /在星辉斑斓里放歌。但我不能放歌, /悄悄是别离的笙箫; /夏虫也为我沉默, / 沉默是今晚的康桥!悄悄的我走了, /正如我悄悄的来;/我挥一挥衣袖, /不带走一片云彩。 4、《荆轲刺秦王》 太子及宾客知其事者,皆白衣冠以送之。至易水上,既祖,取道。高渐离击筑,荆轲和而歌,为变徵之声,士皆垂泪涕泣。又前而为歌曰:“风萧萧兮易水寒,壮士一去兮不复还!”复为慷慨羽声,士皆瞋目,发尽上指冠。于是荆轲遂就车而去,终已不顾。 5、《记念刘和珍君》鲁迅 (1)、真的猛士,敢于直面惨淡的人生,敢于正视淋漓的鲜血。这是怎样的哀痛者和幸福者?然而造化又常常为庸人设计,以时间的流驶,来洗涤旧迹,仅使留下淡红的血色和微漠的悲哀。在这淡红的血色和微漠的悲哀中,又给人暂得偷生,维持着这似人非人的世界。我不知道这样的世界何时是一个尽头!

常见的todo与doing

常见的“to do”与“doing”现象 有些动词后既可接to do,也可接doing,它们后接to do与doing在意思上有时有较大的差别。因为它们也是中考的常考点之一,因而我们应该搞清楚它们的区别。 1. stop to do/stop doing sth。 解析:stop to do sth.意为“停下来(正在做的事)去做(另外的)某事”,to do sth.在句中作目的状语。而stop doing sth.意为“停止做(正在做的)某事”。如Mary stopped to speak to me.玛丽停下(手头的工作)来跟我讲话。 When the teacher came in. the students stopped talking.老师进来时,学生们停止讲话。 2. remember to do/remember doing sth 解析:remember to do sth.意为“记住要去做某事”(还没有做)。而remember doing sth.意为“记得(已经)做过某事”如: Please remember to send the letter for me.请记住为我发这封信。 I don’t remember eating such food somewhere.我不记得在哪里吃过这种食物 3. forget to do/forget doing sth 解析:forget to do sth.意为“忘记做某事”(动作还没有发生)。而forget doing sth.意为“忘记做过某事”(动作已发生)。如: Don’t forget to bring your photo here.别忘了把你的相片带来。 I have forgotten giving the book to him.我忘记我已把书给了他。 4. go on to do/go on doing sth 解析:go on to do sth.意为“做完一件事,接着做另外一件事”,两件事之间有可能有某种联系。而go on doing sth.意为“继续做下去”。如: After reading the text, the students went on to do the exercises.学生们读完课文后,接着做练习。 It’s raining hard, but the farmers go on working on the farm.虽然天正下着大雨,但农民们继续在农场干活。 5. try to do/try doing sth 解析:try to do sth.意为“尽力去做某事”,而try doing sth.意为“(用某一种办法)试着去做某事”。如: Try to come a little early next time, please.下次请尽量早点来。 You can try working out the problem in another way.你可以试试用其它的方法解答这道题目。 6. can’t help to do/can’t help doing sth 解析:can’t help to do为动词不定式结构;can’t help doing sth.意为“身不由己地去做某事”或“情不自禁地去做某事。”如: We can’t help to finish it.我们不能帮忙完成此事。 I couldn’t help laughing when I saw her strange face.当我看到她奇怪的脸时,我情不自禁地笑了。 7. hear sb. do/hear sb. doing sth 解析:hear sb. do sth.意为“听见某人做某事”,指听到了这个动作的全过程;hear sb. doing sth.意为“听到某人做某事”,指听到时候,这个动作正在发生。如: I often hear him sing in the classroom.我经常听见他在教室里唱歌。 Do you hear someone knocking at the door?你听见有人在敲门吗? 应该说明的是:和hear的用法一样的还有see、watch、notice等。

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