个人整理 外贸假发发帘相关知识
各种分类介绍https://www.360docs.net/doc/9716684799.html,/human-hair-exetensions.html
Double drawn:双档齐发Great Lengths hair is double-drawn. This is a laborious manual process whereby shorter strands are removed. Great Lengths perform this process twice- hence the term ‘Double Drawn' which ensures that the volume and thickness of the Great Lengths Hair Extensions strand is consistent all throughout its length.
DOUBLE DRAWN头发是比较饱满的，尾巴的头发比较多
SINGLE DRAWN头发尾部会比较少
Double Weaved: 和片缝利于缝制卡子
Single Weaved：单片缝
是的，卡子发一般会用合片错边的，这样才方便缝卡子
合片的帘子会厚点，单片的比较薄
我们所有的卡子发都是double weaved的WEFT也是合片的
Remy:Great Lengths Hair Extensions uses only ‘Remy hair' from the French word "remis" which means that the hair is collected with the cuticle layer facing the same direction from root to tip just as they do in your natural hair. This collection process is a critical part of ensuring that the hair does not tangle when made into hair extensions.
Remy hair顺发，是人发中的高档货。人的头发是分根部和末梢，顺发就是根部和末梢都在一个方向。
Bonds: The bond is the site where the extension is attached to the natural hair. Great Lengths keratin protein is not a glue. It is a polymer compound whose molecular structure mimics human hair. Many other inferior hair extension methods use other polymers that do not behave like human hair which often lead to the deterioration of the bond and cause the hair to fall out. The Great Lengths Hair Extensions keratin bonds allow the hair to move naturally while at the same time having a strong hold on the hair without causing any damage to the hair shaft.
Cuticle: The cuticle of the hair is the hard, outer layer which acts as a protective barrier for the softer inner structure.
Virgin Hair: The hair is sourced from Indian temples in virgin condition- meaning that the hair has never been treated, bleached or coloured.
Chemically treated : Chemically treated refers to processes such as colouring, bleaching, perming or straightening hair which weakens and damages natural hair structure.
Depigmentation: The process of removing the colour pigment from the hair. Great Lengths uses a gentle osmosis method to remove the colour particles from the hair. No other hair extension company uses this method. Other hair extension companies bleach the hair in order to get the colour out, this destroys the cuticle and overall condition of the hair.
Clip In Hair Extensions: Clip in extensions are temporary extensions that are quick to apply for special occasions. The size of the clip in extensions can vary from one inch wide to a weft that contains 3-5 clips. They're an option of cheaper hair extensions as they're generally made with low quality human hair or synthetic hair. Clip in's can be harder to maintain as they can't be styled as part of your own hair, they need to be washed and dried completely separately. They should be avoided if your hair is too fine - the clips will be visible.
Tape Hair Extensions: Tape weft extensions are semi permanent and very quick to apply. See Great Lengths Fast Track. Application takes between 15-30 minutes and will last up to 12 weeks. Great Lengths Fast Track is the latest innovation in tape hair extensions and is manufactured with a transparent keratin tape bond. The width of each Fast Track strip is similar to a weft (4-5 strips are the equivalent to a full head of prebonded Great Lengths strands) but can be cut in smaller sections by your trained Great Lengths technician. Fast Track wefts lay flat and comfortably in your own hair and are effortless to maintain. Fast track hair is the same premium, ethically sourced ,A-grade hair that you have come to know Great Lengths by.
Micro Links: Also known as Micro Loop or Micro bead hair extensions.Micro Links are beads that are clamped onto the hair shaft. The inside of the bead has grooves (like a screw) which grip onto the hair. This can be damaging to your natural hair. Some micro links are metal which is particularly bad and damaging to your natural hair. When heat is applied to the metal rings, such as a blow dryer or hair straightener, the metal amplifies the heat on the hair inside it resulting in breakage.
Weft: A weft is a continuous hair extension that is either sewn or clipped into the hair. Typically it runs from one ear to the other and falls like a curtain of hair from the attachment area. Unfortunately most wefts are made from artificial hair which is cheaper or low quality human hair.
Weave Hair Extensions: Several sections of your own hair are tightly braided close to the scalp. A weft of hair is then sewn into the braid with a needle and cotton. If braids are made too tightly they can hurt and put strain on your scalp. Weaves are
best for thicker hair because the braids take up a lot of your natural hair. Wefts can be obvious in very fine hair as there is not enough hair left to hide the weft. Weaves are generally made of wefts of artificial hair or low quality human hair. Prebonded Hair Extensions: Also known as fusion hair extensions, iTip,UTip,VTip. Prebonded hair extensions , such a Great Lengths, are the most discrete hair extensions. Great Lengths patented bonds are keratin protein, keratin is the same protein that forms your hair, skin and nails. Because Great Lengths' patented keratin bond mimics the human hair's molecular structure, it makes it compatible with elements such as heat, water and sunlight. Prebonded or fusion hair extensions are the easiest to maintain, you care for them much the same as you would your natural hair. The added benefit is that you have wonderfully thick hair with volume every day for up to six months. If not applied and removed by a trained technician you could risk damage to your natural hair.
https://www.360docs.net/doc/9716684799.html,/faqs.htm巴西发印度发等各种发质优劣的对比
外贸函电复习资料
1.We now have a good demand for the captioned item and therefore write to you _____ establishing trade relations. A.In accordance with B.in the hope of C.for the hope at D.against the hope of 2.Any information you kindly give us will be treated in strict confidence and_____on you part A.without any responsibility B.hasn’t any responsibility C.is no responsibility D.is not to have responsibility 3.we take the liberty of writing to you ____a view to establishing business relations with you A.in B.with C.to D.for 4.pens are packed 12 pieces____a box and 200 boxes___a wooden case. A.to,in B.in,to C.to,to D.to ,of 5.This container can be easily opened___both ends A.By B.on C.at D.in 6.We will refund the premium____you____receipt of your debit note. A.to,upon B.with,upon C.to,at D.with,at
外贸函电期末试题
1.We have established an irrevocable letter of credit (in) your favor with Bank of China, Guangdong. 2.We are glad to enter (into) business relations with your corporation． 3.We are awaiting your revised draft (with) keen interest． 4.Our foreign trade policy is based (on) equality and mutual benefit． 5.We shall book a trial order with you, if goods are competitive (in) price and good (in) quality． 6.As we are heavily committed, we are sorry that we are not in a (position) to accept new orders. 7.We prefer payment by D/P (at) sight to D/P at 60 days． 8.Your quotation happens to be exactly the same (as) we have received from Australia． 9.We hereby register a claim (with) you for shortage． 10.Since we are well connected (with) the department stores here, we can obtain a number of orders for you. 11. You know this is a popular brand, which will sell (well) in your market. 12.We hope that you will look (into) the cause of the defective goods． 13.There is no question (about) getting the necessary import license from our authorities． 14.Please take the necessary steps (without) delay． 15.Your immediate reply should reach us not later (than) the end of this month． 16.If the first shipment is satisfactory, we can (place) with you some repeat orders． 17. We hope this unfortunate incident will not affect the friendly relations (with) us. 18.Please cable us as soon as (possible) , giving us all necessary information． 19.We acknowledge receipt of your letter of March 15, (which) reached us yesterday． 20. (In) view of the long-standing business relations with you, we wish to settle this dispute amicably． 21.We can cover All Risks and War Risk can be covered if the extra premium is borne (by) the buyer． 22.Please do everything necessary (so) as to enable us to send you the relevant documents at an early date． 23.We trust the above-mentioned shipment will reach you (in) sound condition． 24.As to chemical products we are well connected (with) the major producers in America．
外贸函电重点句型
Warm-up exercises Warm-up exercises One 1.我们无意催促你们作出决定，为你方利益着想，建议你们尽快利用此次报盘We have no intention of urging you to make the decision, thinking about for the interests of you, advise you to utilize this offer as soon as possible 2.将我们的报价与其他公司比较后，相信你们会赞同我们所提供的商品价廉物美。 After comparing our quotation with other companies, it is believed that it is good and cheap that you will agree to the goods that we offer. 3.我方欣然接受你们A103号订单订购1，000件“英雄”牌男式衬衣，请按合同规定的条款开立以我方受益人的即期信用证。 We accept your order No. A103 and order 1,000 " hero " brand shirts in men's style joyfully, the clause that please stipulate according to the contract is opened with our beneficiary's sight letter of credit. 4.依照随函附上的详细情况，我们向贵公司订购中国面料。请注意，货物必须与样品完全相符。如果第一份试购单令人满意，我们将继续大量订购。According with the details enclosed, we purchase the Chinese surface fabric from your company. Please note, the goods must be in full conformity with the samples. If the first trial order is satisfactory, we will continue ordering in a large amount. 5.抱歉，不能接受你们的还盘，因我衬衣的报价与当前市场价格相符。 I am sorry, can't accept your counter offer, because the quotation of my shirt is in conformity with market price at present. Warm-up exercises TWO 1.要求定购我们产品的人越来越多。The demand for our products has kept rising. 2.这些报价比其他任何地方都要低得多。 They are still lower than the quotations you can get elsewhere. 3.我想了解一下贵国的投资环境。 I"d like to know some information about the current investment environment in your country. 4.我们相信双方都有一个光明的前景。We are sure both of us have a brighter future. 5.我们的对外贸易政策一向是以平等互利、互通有无为基础的。 Our foreign trade policy has always been based on equality and mutual benefit and exchange of needed goods. Warm-up exercises 3 我认为你推销时不会有任何困难。I don"t think you"ll have any difficulty in pushing sales. 一般你们报盘的有效期是多长？How long will your offer hold good?
芯片是什么 芯片的工作原理 芯片基础知识介绍
芯片是什么芯片的工作原理芯片基础知识介绍 芯片是什么芯片的工作原理芯片基础知识介绍一、芯片基础知识介绍我们通常所说的“芯片”是指集成电路,它是微电子技术的主要产品.所谓微电子是相对'强电'、'弱电'等概念而言,指它处理的电子信号极其微小.它是现代信息技术的基础,我们通常所接触的电子产品,包括通讯、电脑、智能化系统、自动控制、空间技术、电台、电视等等都是在微电子技术的基础上发展起来的。我国的信息通讯、电子终端设备产品这些年来有长足发展,但以加工装配、组装工艺、应用工程见长,产品的核心技术自主开发的较少,这里所说的'核心技术'主要就是微电子技术.就好像我们盖房子的水平已经不错了,但是,盖房子所用的砖瓦还不能生产.要命的是,'砖瓦'还很贵.一般来说,'芯片'成本最能影响整机的成本。微电子技术涉及的行业很多,包括化工、光电技术、半导体材料、精密设备制造、软件等,其中又以集成电路技术为核心,包括集成电路的设计、制造。集成电路(IC)常用基本概念有:晶圆,多指单晶硅圆片,由普通硅沙拉制提炼而成,是最常用的半导体材料,按其直径分为4英寸、5英寸、6英寸、8英寸等规格,近来发展出12英寸甚至更大规格.晶圆越大,同一圆片上可生产的IC 就多,可降低成本;但要求材料技术和生产技术更高。前、后工序:IC制造过程中, 晶圆光刻的工艺(即所谓流片),被称为
前工序,这是IC制造的最要害技术;晶圆流片后,其切割、封装等工序被称为后工序。光刻:IC生产的主要工艺手段,指用光技术在晶圆上刻蚀电路。线宽:4微米/1微米/0.6微未/0.35微米/035微米等,是指IC生产工艺可达到的最小导线宽度,是IC工艺先进水平的主要指标.线宽越小,集成度就高,在同一面积上就集成更多电路单元。封装:指把硅片上的电路管脚,用导线接引到外部接头处,以便与其它器件连接。存储器:专门用于保存数据信息的IC。逻辑电路:以二进制为原理的数字电路。二、电脑芯片的工作原理是什么？是怎样制作的？芯片简单的工作原理：芯片是一种集成电路，由大量的晶体管构成。不同的芯片有不同的集成规模，大到几亿；小到几十、几百个晶体管。晶体管有两种状态，开和关，用1、0 来表示。多个晶体管产生的多个1与0的信号，这些信号被设定成特定的功能（即指令和数据），来表示或处理字母、数字、颜色和图形等。芯片加电以后，首先产生一个启动指令，来启动芯片，以后就不断接受新指令和数据，来完成功能。最复杂的芯片（如：CPU芯片、显卡芯片等）生产过程：1.将高纯的硅晶圆，切成薄片；2.在每一个切片表面生成一层二氧化硅；3.在二氧化硅层上覆盖一个感光层，进行光刻蚀； 4.添加另一层二氧化硅，然后光刻一次，如此添加多层； 5.整片的晶圆被切割成一个个独立的芯片单元，进行封装。一个是电源灯（绿色），一个是硬盘灯（红色），你的电脑开机，
外贸函电复习资料
外贸函电A 一、单项选择题（本大题共20小题，每小题1分，共20分） 在每小题列出的四个备选项中只有一个是符合题目要求的,请将其代码填写在答题纸相应的位置上。错选、多选或未选均无分。 1. We _ __c___ be glad if you could send us samples and quotations. A. shall B. will C. should D. could 2. We have received your enquiry of October 15 __B____ we learn that you are interested in our black tea. A. in which B. from which C. which D. at which 3. We shall appreciate __A____ us your most competitive prices. A. you r quoting B. you quoting C. you to quote D. quote 4. ____C__ your enquiry of 6 September, we are pleased to quote as follows. A. Replying for B. Replying C. Replying to D. To be replied to 5. We agree to the amendments to the contract ___A___ requested in your letter of May 5. A. as B. like C. to be D. when 6. Our offer will remain ___D___ August 31, that is, two weeks from today. A. valid for B. expire C. expiration D. valid till 7. If you find our price ____D__ , please send us an email for our final confirmation. A. acceptance B. accepted C. accepting D. acceptable 8. As soon as we have studied your catalog, we shall ___C___ you by fax. A. contact with B. be contacted with C. contact D. contact to 9. We are sending you by separate airmail a complete set of samples, ___D___ you will find them satisfactory. A. to hope B. hopefully C. in hoping D. hoping 10. To give you a general idea of various goods now available for export, we ____C__ a brochure and a sample. A. enclose you B. enclose C. enclose to you D. enclose for you 11. We would make you the following offer subject to your reply ___A___ us not later than November 25. A. reaching B. arriving C. to reach D. to arrive 12. The Bill of Lading is to be made out ____C__ order. A. to place B. to entertain C. to 按照吩咐 D. for
外贸函电常用语法汇总
(1)贵函YourletterYourfaouryouresteemedletterYouresteemedfaourYouraluedletterYouraluedfaourYournote YourcommunicationYourgreatlyesteemedletterYoureryfriendlynoteYourfriendlyadiceYours. (2)本信，本函Our(my)letterOur(my)respectsOurs(mine)ThislettertheselinesThepresent. (3)前函ThelastletterThelastmailThelastpostthelastcommunicationThelastrespects(自己的信)Thelastfaour(来信) (4)次函ThenextletterThenextmailThenextcommunicationTheletterfollowingthefollowing. (5)贵函发出日期Yourletterof(the)5thMayYourfaourdated(the)5thJuneYoursofthe3rdJulyYoursunderdate(of)the5thJ ulyYourletterbearingdate5thJulyYourfaourofeendate(AE)YourletterofyesterdayYourfaourofyesterd ay''sdateYourletterdatedyesterday. (6)贵方来电、电传及传真YourtelegramYourwireYourcablegram(从国外)Yourcodedwire(密码电报)YourcodemessageYourciphertelegramYourwirelesstelegramYourTELEXYourFax. (7)贵方电话YourtelephonemessageYourphonemessageYourtelephoniccommunicationYourtelephonecallYourri ng. (8)通知(Noun)AdiceNoticeInformationNotificationCommunicationAreportNewsIntelligenceMessage.(erb )(通知，告知)Tocommunicate(afact)toToreport(afact)to...onToapprise(aperson)ofTolet(aperson)knowToacqu aint(aperson)withTointimate(afact)toTosendwordtosendamessageTomailanoticetowrite(aperson)in formationTogienotice(预告)Tobreakanewsto(通知坏消息)Toannounce(宣布). (9)回信(Noun)AnanswerAreplyAresponse.(erb)ToanswerToreplyTogieareplyTogieone''sanswer TomakeananswerTosendananswerTowriteinreplyToanswerone''sletter.(特此回信)ReplytoAnsweringtoInanswertoInreplytoInresponseto.(等候回信)ToawaitananswerTowaitforananswer.(收到回信)TogetananswerTofaouronewithananswerTogetaletteranswered. (10)收讫，收到(Noun)Receipt(收到)Areceipt(收据)Areceier(领取人，取款人)Arecipient(收款 人)(erb)ToreceieTobeinreceiptofTobeto(at)handTocometohandTobeinpossesionofTobefaouredwith TogetTohaeTohaebefore(aperson)Tomakeoutareceipt(开出收据)Toacknowledgereceipt(告知收讫). (11)确认ToconfirmConfirmingConfirmationInConfirmationof(为确认...,为证
2019年自考外贸函电考试重点自考小册子最新版
一、外贸函电的写作要领：completeness（完整）、concreteness（具体）、clarity（清楚）、 conciseness（简洁）、courtesy（礼貌）、consideration（体谅）以及correctness（正确）。 二、信息可以分为四大类：肯定信息（positive message）、中性信息（neutral message）、 否定信息（negative message，也称负面信息）和说服信息（persuasive message）. 三、布局可以分为平铺直叙法（Direct Plan or Approach）和曲折迂回法（Indirect Plan or Indirect Approach）。 四、书信的组成部分 （必备部分）（可选部分） 1.信头（The Heading） 8、事由( The Subject Heading Or Caption) 2.日期（Date Line） 9、经办人（Attention line） 3.封内地址（The Inside Address） 10、附件（The Enclosure）简写Encl. or Enc. 4.称呼（The Salutation） 11、抄送（Carbon Copy）简写C.C. 5.信的正文（The Body of the Letter） 12、再启（The Postscript）简写P.S. 6.结束语（The Complimentary Close） 7.签名（The Signature） 五、打信格式 1.缩行式：封内地址和其需要分行的地址的后一行，都比前一行缩进两格或三格；信的正 文，每一段的开始一行都缩进若干格（一般与称呼末一字母取齐）。 2.平头式：需要分段的地方，及每段的开始一行都与前一行取齐，一律不缩行。平头式各 段之间要用double space以示分段。 3.混合式：封内地址和称呼采用平头式（从左边的空白边缘打起），其他部分采用缩行式， 两种格式的混合采用所以称之为混合式。 八、撰写询函的理由通常包括： （1）获取信息（如价格和技术数据） （2）获得印刷品（如商品目录本、说明书、公司介绍等） （3）索取样品 （4）取得帮助（如得到特别允许，帮助或建议等）
晶片相关知识
晶片相关知识讲述
第一节：LED 制程简介； 第二节：晶片的制做原理及组成原料； 第三节：晶片的特性及发光原理； 第四节：常用晶片的种类； 第五节：晶片的分片方式； 第六节：晶片的正确使用及影响因素。
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第一节：LED 制程简介
发光二极体：Light Emitting Diode（LED）是一种具有两个电极端 子、在电子间施加电压，通过电流会立即发光的光电元件。 由于 LED 是自体发光，用手触摸并不会有热的感觉，且寿命可达 十万个小时以上。 LED 依制作流程可分为上、中、下游与应用四个部份。 上游制程主要是单晶棒经由切割、研磨、抛光，而形成单晶片。 单晶片为磊晶成长用基板。 磊晶片透过不同磊晶成长法，制造Ⅲ Ⅴ族化合物半导体，如：磷 化镓 （GaP） 砷化镓 、 （GaAs） 磷砷化镓(AsGaP) 、 、 砷化铝镓 （AlGaAs） 、 磷化铝铟镓（AlGaInP） 、氮化铟镓（GaInN）等磊片，然后进入中游制 程。 下游制程主要是封装完成 LED 成品。将晶粒粘著（Dice Bond） 、打 线（Wire Bond）后，置入树脂的模具中，封装完成不同基本零件或模组， 等树脂硬化后取出剪脚，完成 LED 成品。若依封装成品可分为灯泡型 (Lamp) 、 数 字 / 字 元 显 示 型 (Digital/Character) 、 表 面 粘 著 型 (Surface Mount) 、点矩阵型 (Dot Matrix) 、集束型(Chuster)等。而使用 LED 成 品制作成显示器材，则属于应用层面。 应用：户外显示屏幕、第三煞车灯、交通记号等。 LED 具有低耗电量、低发热量、使用寿命长、反应速率快、耐震性 高等特性、是符合环保要求的光电元件。应用于资讯、通讯、消费性电 子等方面。
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外贸函电复习词汇
外贸英语函电复习资料 1、general merchandise杂货 2、trade terms贸易条款、条件（常用复数） 3、under separate cover 另函附上 4、for your reference 以供参考 5、receive our immediate attention 得到立即处理 6、our mutual benefit 相互利益 7、in duplaicate一式两份（duplicate 副本、复制品） triplicate三份、quadruplicate四份、quintuplicate五份、sextuplicate六份 8、terms of payment 付款方式 9、firm offer实盘、不能撤销的发价 10、an inquiry sheet 一份询价单 11、most favorable prices最优惠的价格 12、place large orders 大量订购 13、delivery date 交货期 14、specific inquiry 具体询价 15、subject to our final confirmation 以我方最后确认为准 16、attractive price 具有吸引力的价格 17、international market price 国际市场价 18、retail price零售价 19、wholesale price 批发价 20、net operating income营业净收入 21、longstanding business relations 长期的业务关系 22、out of line 不一致23、purchase the goods elsewhere 到他处订货 24、accept your quotation 接受你方报价 25、purchase order购货订单 26、in your favor 以你方为抬头 27、prompt shipment 迅速装船 28、shipping marks运输标志，俗称唛头 29、certificate of origin原产地证明书 30、gross weight 毛重，即商品本身的重量加包装的重量 31、trial order初试订货 32、effect delivery发运 33、up to our expectation 合乎我方要求 34、ready for delivery（货已备妥）待发 35、shipping advice 装运通知，装船通知 36、documents against payment 付款交单 37、arrange shipment 安排装运 38、not correspond to不符合 39、a special accommodation 特殊照顾 40、partial shipment 分装 41、transshipment转船 42、suitable for ocean transportation 适合于海运 43、take into account 珍惜 44、opening the L/C 开立信用证 45、extension of L/C 信用证延期 46、shipping document = export document 运输单据 47、packing list 装箱单 48、advance shipment 提前转运
外贸函电重点整理
Unit 1 Business Letter Writing 商业书信撰写 1.The Salutation 称呼 这是写信人对收信人的一种称呼，其位置是在封内地址的下面空两行，目前外贸书信中一般通用的称呼语有：Dear sir , Dear Madam, Dear Sirs,Dear Mesdames, Gentlemen(不能用单数),Dear Mr.xxx https://www.360docs.net/doc/9716684799.html,plimentary Close 结束客套语 结束语是一种客套用语它应与前面的称呼相呼应，后面加逗号。如： Dear Sir(s): Yours faithfully,or Faithfully yours, Gentlemen: Truly yours,or Yours truly, Dear Mr.xx, Yours sincerely or Sincerely yours, 3.Enclosure 附件 如信中有附件时，应在签名下注明Encl.或Enc.如附件不止一件应注明2 Encls or 3 Encls,或详细列明如下： Encls: 2 Invoices Enc: 1 Photo 1 Certificate 4.
5. 6. Unit 2 Establishing Business Relations 建立业务关系1．说明信息来源（The source of information） Your company has been kindly introduced to us by… we learn from…that… 简单介绍自己公司（brief introduction to your own company ） We wish to introduce ourselves to you as… Our lines are mainly …
7107芯片相关知识
ICL7107电路图 ICL7107 安装电压表头时的一些要点：按照测量＝±199.9mV 来说明。 1.辨认引脚：芯片的第一脚，是正放芯片，面对型号字符，然后，在芯片的左下方为第一脚。 也可以把芯片的缺口朝左放置，左下角也就是第一脚了。 许多厂家会在第一脚旁边打上一个小圆点作为标记。 知道了第一脚之后，按照反时针方向去走，依次是第 2 至第40 引脚。（1 脚与40 脚遥遥相对）。 2.牢记关键点的电压：芯片第一脚是供电，正确电压是DC5V 。第36 脚是基准电压，正确数值是100mV，第26 引脚是负电源引脚，正确电压数值是负的，在－3V 至－5V 都认为正常，但是不能是正电压，也不能是零电压。芯片第31 引脚是信号输入引脚，可以输入±199.9mV
的电压。在一开始，可以把它接地，造成“0”信号输入，以方便测试。 3.注意芯片27,28,29 引脚的元件数值，它们是0.22uF,47K,0.47uF 阻容网络，这三个元件属于芯片工作的积分网络，不能使用磁片电容。芯片的33 和34 脚接的104 电容也不能使用磁片电容。 4.注意接地引脚：芯片的电源地是21 脚，模拟地是32 脚，信号地是30 脚，基准地是35 脚，通常使用情况下，这 4 个引脚都接地，在一些有特殊要求的应用中（例如测量电阻或者比例测量），30 脚或35 脚就可能不接地而是按照需要接到其他电压上。－－本文不讨论特殊要求应用。 5.负电压产生电路：负电压电源可以从电路外部直接使用7905 等芯片来提供，但是这要求供电需要正负电源，通常采用简单方法，利用一个+5V 供电就可以解决问题。比较常用的方法是利用ICL7660 或者NE555 等电路来得到，这样需要增加硬件成本。我们常用一只NPN 三极管，两只电阻，一个电感来进行信号放大，把芯片38 脚的振荡信号串接一个20K －56K 的电阻连接到三极管“B”极，在三极管“C”极串接一个电阻（为了保护）和一个电感（提高交流放大倍数），在正常工作时，三极管的“C”极电压为 2.4V － 2.8V 为最好。这样，在三极管的“C”极有放大的交流信号，把这个信号通过 2 只4u7 电容和 2 支1N4148 二极管，构成倍压整流电路，可以得到负电压供给ICL7107 的26 脚使用。这个电压，最好是在－3.2V 到－4.2V 之间。 6.如果上面的所有连接和电压数值都是正常的，也没有“短路”或者“开路”故障，那么，电路就应该可以正常工作了。利用一个电位器和指针万用表的电阻X1 档，我们可以分别调整出50mV,100mV,190 mV 三种电压来，把它们依次输入到ICL7107 的第31 脚，数码管应该对应分别显示50.0,100.0,190.0 的数值，允许有 2 －3 个字的误差。如果差别太大，可以微调一下36 脚的电压。 7.比例读数：把31 脚与36 脚短路，就是把基准电压作为信号输入到芯片的信号端，这时候，数码管显示的数值最好是100.0 ，通常在99.7 －100.3 之间，越接近100.0 越好。这个测
外贸函电复习资料
I. Choose the best (Choices are provided when exam is taken - Advisable to have the blanks filled with proper words by consulting your dictionary or other reference books NOW.) 01 Although (much as)_ we would like to close the business with you, we find your bid unacceptable. 02 _If (in case)_ you like other items, kindly let us know and we shall be only too pleased to make you offers direct. 03 According to the contract stipulation, shipping marks are _ at the buyer's option_. 04 According to the nature of the cargo, this cover _ is subject to _ a 5% franchise. 05 According to the shipping _schedule____ it will be impossible for us to ship the goods in October. 06 After inspection of the above shipment we found 5 cases _missing_. 07 As agreed upon in our negotiations, payment __ is to be made by __ L/C. 08 As it _involves____ only a small quantity, we hope you will have no difficulty in settling this matter. 09 As we are in the market for auto parts, we should _ be pleased___ if you would send us your best quotations. 10 Before shipment, the buyers generally send their __ shipping requirements __ to the sellers, informing them of the packing and mark, mode of transportation, etc. 11 By joint efforts we can _promote___ both friendship and business. 12 Fifty cases of Green Tea you sent us were found to be badly damaged. This was apparently attributable to _ inferior _ packing. 13 Generally we cover insurance _ in the absence of _ definite instructions from our clients. 14 If our salutation is "Dear Mr. White", our complimentary close should be _ Yours sincerely (BrE)/Yours truly (AmE) __. 15 If you fail to make punctual shipment, we will have to ask you to compensate us for any loss arising _ therefrom _. 16 It is up to you to _see that___ the job’s properly done. 17 In reply _to___ your fax of October 16, we would like to give you the following information. 18 Necessary certificates __ in regard to_ the quality and quantity of the shipment will be provided. 19 Our goods are __of__ fine quality and __of__ attractive designs, we believe you will have no difficulty in _disposing____ them at our price. 20 Our offer is subject __to_ your acceptance promptly. 21 Payment is to be made by letter of credit payable _against___ shipping documents. 22 Please amend the credit as allowing transshipment. 23 Please be informed that the quotation _is subject to _ change without previous notice. 24 Referring to Contract No. 11, we are agreeable _to___ D/P payment terms. 25 Since the premium varies with the scope of _ insurance_, extra premium is for buyer’s account, should additional risks be covered? 26 The analysis of the first shipment is not satisfactory _as is_ certified by the China Commodity Inspection Bureau. 27 The lid was broken and the case with its contents crushed. It looks __ as if __ the case was not strong enough to stand the voyage.
晶体相关基础知识
石英晶体基本常识 一、基础概念 1、石英晶体谐振器:利用石英晶体的逆电压效应制造具有选择频率和稳定频率的无线电元件。 电介质由于外界的机械作用，(如压缩?伸拉)而在其內部产生变化，产生表面电荷的现象，叫压电效应，如果将具有压电效应的介质至于外电场中，由于电场的作用，会引起介质內部正负电荷中心位移，而这一位移产生效应为逆压电效应 2、晶片的主要成分SiO2（二氧化硅）密度：2.65g/cm3分子量：60.06 3、振动模式晶体分为以下两类： AT 基频：BT 在振动模式最低阶次的振动频率 CT DT 3次 泛音：5次晶体振动的机械谐波，泛音频率与基频频率之比， 7次接近整倍数，又不是整倍数。 9次 AT与BT如何区分 1)通过测量晶片厚度 AT厚度t=1670/F0 F0-晶体标称频率 BT厚度t=2560/F0 2)通过温选根据晶片的拟合曲线来确定 3)通过测量晶体的C0、C1、TS、L、T来确定 4、按规格分为：HC-49S，HC-49U，HC-49S/SMD，表晶(3*8、2*6)，UM系列等 HC-49S HC-49U HC-49S/SMD 表晶 陶瓷SMD 钟振UM系列 5、标称频率：晶体技术条件中所给定的频率，如4.000MHz，12.000MHz，25.000MHz等 6、调整频差：在规定条件下，基准温度时，工作频率相对于标称频率所允许的偏离值(如： ±30ppm、±25ppm)
7、串联谐振频率(FR)：晶体本身固有的频率 8、负载谐振频率(FL)：在规定条件下，晶体与一负载电容相并联或相串联，其组合阻抗呈现 出来的谐振频率。 9、负载电容：在振荡电路中晶体两脚之间所有的等效电容量之和.在通常情况下IC厂家在规格书中都会给出推荐的晶体匹配电容. 说明：负载电容CL是组成振荡电路时的必备条件。在通常的振荡电路中，石英晶体谐振器作为感抗，而振荡电路作为一个容抗被使用。也就是说，当晶体两端均接入谐振回路中，振荡电路的负阻抗-R和电容CL即被测出，这时，这一电容称为负载电容。负载电容和谐振频率之间的关系不是线性的，负载电容小时，频率偏差量大，当负载电容提高时，频率偏差量减小。当振荡电路中的负载电容减少时，谐振频率发生较大的偏差，甚至当电路中发生一个小变化时，频率的稳定性就受到巨大影响。负载电容可以是任意值，但10-30PF会更佳。 10、温度频差(F/T)：在规定条件下，工作温度范围内，相对于基准温度时工作频率允许的偏离 值 11、基准温度：25±2℃，湿度：50%±10% 12、谐振电阻(RR)：在规定条件下，晶振在谐振频率时的等效电阻 13石英晶体谐振器等效电路 石英晶体谐振器的振动实质上是一种机械振动。实际上，石英晶体谐振器可以被一个具有电子转换性能的两端网络测出。这个回路包括L1、C1，同时C0作为一个石英晶体的绝缘体的电容被并入回路，与弹性振动有关的阻抗R1是在谐振频率时石英晶体谐振器的谐振阻抗。(见图1)