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IF的使用--零条件,第一条件,第二条件,第三条件

IF的使用--零条件,第一条件,第二条件,第三条件
IF的使用--零条件,第一条件,第二条件,第三条件

语法要点2

if使用小窍门

在"if"引导的从句中,我们通常谈论不确定的事件和情况。

我们使用"if"来强调事情发生的条件。

另一种通常的用法是表明"if it is true that"。

特殊的时态能用于"if"之后来表示事情是想象中的。

最后,一个"if-clause"经常是这样的情形--一些事情必须在此之前发生,以后的事才能发生。

Zero Conditional: certainty

We use the so-called zero conditional when the result of the condition is always true, like a scientific fact.

第一种情况我们称为“零条件”,在这种情况下由条件引起的结果通常都是事实,比如科学现象。

IF condition result

present simple present simple

If you heat ice it melts.

First Conditional: real possibility

We are talking about the future. We are thinking about a particular condition or situation in the future, and the result of this condition.

There is a real possibility that this condition will happen. For example, it is morning. You are at home. You plan to play tennis this afternoon. But there are some clouds in the sky. Imagine that it rains. What will you do?

第二种情形,我们称之为“第一条件”,表示在将来某个条件或前提下,会产生某个结果。这个发生在将来的前提条件确实可能发生。

IF condition result

present simple WILL + base verb

If it rains I will stay at home.

Second Conditional: unreal possibility or dream The second conditional is like the first conditional. We are still thinking about the future. We are thinking about a particular condition in the future, and the result of this condition. But there is not a real possibility that this condition will happen. For example, you do not have a lottery ticket. Is it possible to win? No! No lottery ticket, no win! But maybe you will buy a lottery ticket in the future. So you can think about winning in the future, like a dream. It's not very real, but it's still possible.

第三种情形,我们称之为“第二条件”,表示在将来某个条件或前提下,会产生某个结果。这个发生在将来的前提条件不太可能发生,但仍有发生的可能性。

IF condition result

past simple WOULD + base verb

If I won the lottery I would buy a car.

Third Conditional: no possibility

The first conditional and second conditionals talk about the future. With the third conditional we talk about the past. We talk about a condition in the past that did not happen. That is why there is no possibility for this condition. The third conditional is also like a dream, but with no possibility of the dream coming true.

Last week you bought a lottery ticket. But you did not win.

第四种情形,我们称之为“第三条件”,表示在过去某个条件或前提没有发生,只是想象在这样的前提下会产生某个结果。

IF condition result

Past Perfect WOULD HAVE + Past Participle If I had won the lottery I would have bought a car.

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标准件选用手册(2015版)

标准件选用手册

目次 1紧固件产品分类 (1) 1.1按大类分 (1) 1.2螺栓连接的分类 (1) 1.2.1按受力形式分类 (1) 1.2.2根据安装状态分类 (1) 1.2.3按产品等级分类 (2) 1.3按采用产品的螺纹分类 (2) 1.4按螺栓材料与性能等级分类 (2) 1.5高强度螺栓简单分类 (2) 2紧固件常用螺纹 (2) 2.1基本尺寸 (2) 2.2普通螺纹公差与配合的选用 (2) 2.3普通螺纹的标记 (5) 2.4自攻(含锁紧)螺钉用螺纹、螺杆螺纹 (5) 2.4.1自攻螺钉用螺纹 (5) 2.4.2自攻锁紧螺钉的螺杆粗牙普通螺纹系列 (6) 3紧固件的机械性能 (6) 3.1螺栓、螺钉、螺柱的机械性能 (6) 3.1.1适用范围 (6) 3.1.2 螺栓、螺钉、螺柱的性能等级 (6) 3.1.3 材料和热处理、回火温度 (6) 3.1.4 螺栓、螺钉和螺柱的机械和物理性能 (7) 3.1.5 粗牙螺纹最小拉力载荷 (8) 3.1.6 粗牙螺纹保证载荷 (9) 3.1.7 细牙螺纹最小拉力载荷 (10) 3.1.8 细牙螺纹保证载荷 (11) 3.2螺母(粗牙、细牙)的机械性能 (12) 3.2.1 适用范围 (12) 3.2.2 螺母粗牙螺纹的性能等级 (12) 3.2.3 螺母细牙螺纹的性能等级 (17)

3.3 自攻螺钉 (20) 3.3.1金相与硬度 (20) 3.3.2机械性能 (21) 3.4抽芯铆钉 (21) 3.4.1机械性能等级 (21) 3.4.2机械性能 (22) 3.5 蝶形螺母保证扭矩 (22) 4 紧固件的连接方式选用 (22) 4.1紧固件的连接特性及基本要求 (22) 4.1.1紧固件连接的受力和传力方式 (22) 4.1.2紧固件连接的失效形式 (23) 4.1.3紧固件连接设计的基本要求 (23) 4.2螺栓连接的预紧 (23) 4.2.1预紧的目的 (23) 4.2.2预紧力的确定 (23) 4.2.3拧紧力矩 (24) 4.2.3.1拧紧力矩的计算 (24) 4.2.3.2紧固件的拧紧扭矩 (24) 4.2.4预紧力的控制方法 (27) 4.3螺纹连接的防松 (27) 5紧固件的选用原则 (27) 5.1正确选择紧固件的外形 (27) 5.2选用适合的精度等级 (28) 5.3选择适用的紧固件材料 (28) 5.4选用合适的表面处理方法 (29) 6标准件选用范围及标注 (29) 6.1标准件分类 (29) 6.2标准件明细 (29) 6.3标准件的选用范围 (29)

标准件编码规则

标准件编码规则: 4.7标准零件及材料按照下列方法执行 ●用六位数字代表; ●前两位数字是代表每种零件及材料的类别; ●后四位数字是代表该类零件及材料的顺序号。 例如:电源线的物料编码是“020001”, 物料编码的前两位数字“02”表示材料的类别, 后四位代表材料的顺序号。 物料编码前两位数字代表的类型如下: 4.7.1“01”代表电器类,包括以下几种零件及材料: ●碳刷用零件及材料; ●接线用零件及材料; ●焊丝、焊条; ●离心开关的零件及材料; ●电工用零件及材料(如:永磁铁、换向器、集电环等); ●热敏电阻; ●继电器。 4.7.2“02”代表电线电缆类,主要包括以下几种: ●电动机用引出线(JBQ、JFEM等电线、电缆); ●电源线用电线、电缆; ●单支线。 4.7.3“03”代表化工类,主要包括以下几种: ●漆类(电动机表面漆、绝缘漆、马路漆等); ●油类(机油、柴油等); ●理化化验用材料; ●脂类(硅脂、树脂、锂基脂等); ●电工用化工材料(水银、松香等); ●剂类(稀释剂、固化剂、脱漆剂等); 4.7.4“04”代表有色金属,主要包括以下几种; ●铜材料类(板、棒、管) ●铝材料类(锭、板、棒、管);

4.7.5“05”代表黑色金属,主要包括以下几种: ●钢材类(不锈钢、键钢、模具钢、弹簧钢、碳素钢等板、棒、管等); ●角钢类。 4.7.6“06”代表五金紧固件,主要包括以下几种: ●螺栓类; ●螺钉类; ●螺母类; ●垫圈类; ●挡圈类; ●铆钉类; ●销类; ●弹簧类(压力弹簧、波形弹簧); ●键类; ●铁钉类。 4.7.7“07”代表绝缘材料,主要包括以下几种: ●绝缘板类(环氧酚醛布板、层压板、胶版); ●绝缘薄膜类; ●绝缘纸类; ●绝缘布类; ●绝缘管类; ●绝缘套类; ●电工用绑扎带类; ●工业油毛毡。 4.7.8“08”代表塑料制品,主要有以下几种: ●密封类(O形密封圈、密封圈、引线胶圈、油封等); ●电动机塑料风扇; ●塑料套类(轴套、线帽、螺套等); ●管类(塑料管、热缩管等); ●袋类(文件袋、密实袋等)。 4.7.9“09”代表漆包线。 4.7.10“10”代表轴承,主要有以下几种:

if可以引导真实条件句和虚拟条件句

Unit 4 一. if 条件句 if可以引导真实条件句和虚拟条件句。真实条件句表示在假设的条件下,能够实现的情况。在这种情况下,主句和从句的谓语动语随各自的人称和时态发生变化,同时if条件句遵循“主将从现”的原则,即主句用一般将来时,从句用一般现在时表将来。 If it doesn’t rain tomorrow, we will go for a picnic. 如果明天不下雨,我们去野餐。 如果if条件句用来描述说话人认为与事实相反的内容,或仅是一种愿望,假设、猜测等,我们称为虚拟条件句。 If I got rich , I would travel around the world. 如果我有钱了,我将周游全世界。 1. —I often get nervous when I have an English class. What should I do?

—If I were you, I . (ask the English teacher for help) 2. —What would the earth be like if there ?(is no air or water on it) —It could be like the moon without any living things. 3. If it ,the crops would be saved. (is to rain tomorrow) 4. If we had found him earlier, we .(solve the problem more easily) 5. If I hadn’t been so busy, I .(take part in the party) 四、单选。 ( )1. If my father here now, he tell me what to do. A. were, would B. were, will C. is would D. is will ( )2. If I a bee, I work much harder. A. were, would B. were, shall C. had, will D. have, should ( )3. If I much money, I buy a house. A. have, will B. had, would C. had, will D. have, should ( )4. He learn more quickly if he harder. A. will, work B. would , worked C. would, work D. will, worked ( )5. If I you, I do that. A. was, wouldn’t were, wouldn’t C. am, won’t D. were, won’t ( )6. It’s quite impossible that it will rain tomorrow. But if it ,I would still go to the park. A. should rains B. would rain C. rained D. had rained 五、汉泽英 1. 如果我是你,我会帮助她。If I you, I her. 2. 如果我以前去过那个地方,我就认识路了。(和相反) If I to the place before, I the way. 3. 万一你明天迟到了,我们就不等你了。(和相反) If you tomorrow, we for you.=If you late tomorrow, we for you. 4. 如果没有空气,地球上就不存在生物。 If there no air, there no living things.

润滑油管理制度

润滑油管理制度 一、润滑油的工作任务 设备部对润滑管理方面担负的工作任务有下列项目: 1、建立并完善各项润滑管理工作制度和办法。 2、组织编制润滑工作所需的各种基础技术管理资料; 3、指导有关人员按润滑要求搞好在用设备的润滑工作; 4、实行定额用油管理,按期向采购部提出年、季度润滑油品需用量的申请计划,并按月把指标分解落实到车间、班组及单台设备; 5、实施进厂油品的质量检验,禁止发放不合格油品; 6、组织编制年、季、月设备清洗换油计划和储油箱油质化验计划。实施按油质情况确定最佳换油时间; 7、做好设备润滑状态的定期检查与加油,及时采取改善措施,完善润滑装置,防止油料变质,治理漏油,消除油料浪费; 8、组织油品的回收与再生利用工作; 9、收集油品生产厂家研制新油品的信息,逐步做好进口设备用油国产化,做好短缺油品的代用与掺配工作; 10、组织润滑工作人员的技术培训,学习国内外先进经验,推广应用润滑新技术,新材料和新装置,不断提高企业润滑管理工作的水平。 二.润滑材料供应管理制度

1、采购部根据生产设备部提出的年度、季度及月份润滑材料申请计划,如期按牌号、数量、质量采购供应; 2、进厂油品一定要经化验部门检验其主要质量指标,合格后方可发放使用,对不合格油品,要求供应厂家退换或采取技术处理措施; 3、采购部门对供应紧缺的油品,应提前与设备管理部门研究采取代用油品,以免供应脱节,影响使用; 4、入库油料必须专桶专用,标明牌号,分类储存,转桶时应过滤,所有油桶都要将盖子盖好。露天存放时,桶盖部位应抬高一些,以防止雨水和杂质进入桶内; 5、润滑站发现领到的油品质量有问题时,应立即通知润滑工程师和采购部门到现场处理,不得随意发放; 6、润滑材料在库存放一年以上者,油库应送化验部门重新检验油品质量,未取得合格证者禁止发放使用,并应及时采取计划处理措施。 三.润滑油站管理制度 润滑油站按照任务分工,负责各种油料的收发保管,废油的回收再生与利用,切削液等工艺用油的配制与发放。 对润滑站的管理作如下规定: 1、油库的各种设施必须符合有关安全规程,严格遵守安全防火制度,按特级防火区要求设置防火设施,对消防检查中提出的问题要限期解决;

if条件句和should的用法

If 引导条件句的用法 1、真实条件句用于陈述语气,假设的情况可能发生,其中if 是如果的意思。时态关系 句型:条件从句主句 一般现在时shall/will + 动词原形 If he comes, he will bring his violin. 典型例题 The volleyball match will be put off if it ___. A. will rain B. rains C. rained D. is rained 答案B。真实条件句主句为将来时,从句用一般现在时。 注意: 1)在真实条件句中,主句不能用be going to表示将来,该用shall, will. (错) If you leave now, you are never going to regret it. (对) If you leave now, you will never regret it. 2)表示真理时,主句谓语动词便不用shall (will) +动词原形,而直接用一般现在时的动词形式。 2 非真实条件句 1)时态:可以表示过去,现在和将来的情况。它的基本特点是时态退后。 a. 同现在事实相反的假设。 句型:条件从句主句 一般过去时should( would) +动词原形 If they were here, they would help you. b. 表示于过去事实相反的假设。 句型:条件从句主句 过去完成时should(would) have+ 过去分词 If she had worked harder, she would have succeeded. The rice would not have been burnt if you had been more careful. If my lawyer had been here last Saturday, he would have prevented me from going. If he had come yesterday, I should / would have told him about it. 含义:He did not come yesterday, so I did not tell him about it. If he had not been ill and missed many classes, he would have made greater progress. 含义:He was ill and missed many lessons, so he did not make greater progress. c. 表示对将来的假想 句型:条件从句主句 一般过去时should+ 动词原形 were+ 不定式would + 动词原形 should+ 动词原形

英语专项 语法 时态 14 条件句之第二条件 讲解+练习+答案 second conditional

Second Conditional 第二条件句 主谓模块 ? If I won the lottery, I would buy a big house. 要是我(哪天)中了彩票,我就会买一个大房子。 ? If I were you, I wouldn’t eat that. 要是我(现在)是你的话,我就不会吃那个东西。 用法总结 First, we can use it to talk about things in the future that are probably not going to be true. Maybe I'm imagining some dream for example. 首先,我们可以用它来谈论将来不太可能会发生的事情,好像在做白日梦一样。? If I met the Queen of England, I would say hello. 要是我(哪天)碰到了英格兰女王,我就会跟她打个招呼。 ? She would travel all over the world if she were rich. 她会环游世界,如果她(哪天)有钱了的话。 We can use it to talk about something in the present which is impossible, because it's not true. 第二,我们可以用它来谈论与现在的实际情况相反的假设,有点不满现状或想改变现状的感觉。 ? If I had his number, I would call him. (I don't have his number now, so it's impossible for me to call him). 如果我(现在)有他的电话号码,我就给他打电话。 (我现在没有他的电话号码,所以我不可能给他打电话)。 ? If I were you, I would go out with that man. (I am not you now, so it's impossible for me to go out with that man). 如果我(现在)是你的话,我就会和那个人出去。 (我现在不是你,所以我不可能和那个人出去)。

制图标准件题库答案

高职版《机械制图》期末考试试题库 第八章标准件和常用件 一.读螺纹标记并填表 螺纹标记螺纹 种类内外 螺纹 公称 直径 螺 距 导 程 线 数 旋 向 旋合 长度 公差带代号 中径顶径 M24×1.5-5g6g-S 三角外24 1.5 1.5 1 右短5g 6g M20×2LH-6H-L 三角内20 2 2 1 左长6H 6H Tr40×14(P7)-8H 梯形内40 7 14 2 右中等8H / 二.螺纹填空 三.写出螺纹规定的标记 1、粗牙普通螺纹公称直径16毫米,右旋,中径顶径6g,中等旋合长度。 M16-6g 2、普通螺纹公称直径20毫米,螺距2毫米,左旋,中径公差带5H,顶径公差带6H,长旋合长度。 M20×2LH-5H6H-L 3、梯形螺纹公称直径52毫米,导程14毫米,螺距7毫米,双线,左旋,中径公差带7H,中等旋合长度。 Tr52×14(P7)LH-7H 4、梯形螺纹公称直径40毫米,螺距7毫米,单线,右旋,中径公差带8e,长旋合长度。 Tr40×7-8e-L 5、普通螺纹公称直径10毫米,螺距1毫米,右旋,中径6g,顶径7g,中等旋合长度。 M10×1-6g7g 6、梯形螺纹公称直径28毫米,螺距5毫米,单线,右旋,中径公差带8f,中等旋合长度。 Tr28×5-8f 四.螺纹画法 1、将螺纹画法错误的地方在下面改正 2、将螺纹画法错误的地方在下面改正 螺纹标记 螺纹 种类内外 螺纹 公称 直径 螺 距 导 程 线 数 旋 向 旋合 长度 公差带代号 中径顶径 M20×1.5-5H-L 三角内20 1.5 1.5 1 右长5H 5H M16×1.5LH -5g6g- L 三角外16 1.5 1.5 1 左长5g 6g Tr40×14(P7)LH-7e 梯形外40 7 14 2 左中等7e / 螺纹标记螺纹 种类内外 螺纹 公称 直径 螺 距 导 程 线 数 旋 向 旋合 长度 公差带代号 中径顶径 M24×2-6g 三角外24 2 2 1 右中等6g 6g M20×1.5-6h7h-S 三角外20 1.5 1.5 1 右短6h 7h Tr52×16(P8)-8H 梯形内52 8 16 2 右中等8H /

切削液使用管理规定

内部 切削液使用管理规定

2016年4月8日

发放:一车间、五车间、九车间、经营管理处、质量检验处 编制: 校对: 审核: 批准:

合理选用冷却润滑液,可以有效地减小切削过程中的摩擦,改善散热条件,而降低切削力,切削温度和刀具磨损,提高刀具耐用度,切削效率和已加工表面质量及降低产品的加工成本。随着科学技术和机械加工工业的不断发展,特别足大量的难切削材料的应用和对产品零件加工质量要求越来越高,这就给切削加工带来了难题。为了使这些难题获得解决,除合理选择别的切削条件外,合理选择切削液也尤为重要。 2 切削的分类 2.1水溶液 其主要成分是水。由于水的导热系数是油的导热系数三倍,所以它的冷却性能好。在其中加入一定量的防锈和汕性添加剂,还能起到一定的防锈和润滑作用。 2.2 乳化液: 2.2.1普通乳化液:它是由防锈剂,乳化剂和矿物油配制而成。清洗和冷却性能好,兼有防锈和润滑性能。 2.2.2防锈乳化液:在普通乳化液中,加入大量的防锈剂,其作用同上,用于防锈要求严格的工序和气候潮湿的地区。 2.2.3极压乳化液:在乳化液中,添加含硫,磷,氯的极压添加剂,能在切削时的高温,高压下形成吸附膜,起润滑作用。 2.3切削油: 2.3.1矿物油:有5#、7#、10#、20#、30#机械油和柴油,煤油等,适用于一

2.3.2动,植油及复合油:有豆油、菜子油、棉子油、蓖麻油、猪油等。复合油是将动、植、矿三种油混合而成。它具有良好地边界润滑。 2.3.3 极压切削油:它是以矿物油为基础,加入油性,极压添加剂和防锈剂而成。具有动,植物油良好地润滑性能和极压润滑性能。 3 切削液的作用 3.1 冷却作用 它可以降低切削温度,提高刀具耐用度和减小工件热变形,保证加工质量。一般的情况下,可降低切削温度50~150℃。 3.2 润滑作用 它可以减小切屑与前刀面,工件与刀具后刀面的摩擦,以降低切削力,切削热和限制积屑瘤和鳞刺的产生。一般的切削油在200℃左右就失去润滑能力。如加入极压添加剂,就可以在高温(600~1000℃)、高压(1470~1960MPa)条件下起润滑作用。这种润滑叫做极压润滑。 3.3 清洗作用 它可以将粘附在工件,刀具和机床上的切屑粉末,在一定压力的切削液作用下冲洗干净。 3.4 防锈作用 防止机床、工件、刀具受周围介质(水分、空气、手汗)的腐蚀。 4 冷却润滑液中的添加剂 4.1 油性添加剂

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