Lesson 5 lathe, shaper, grinding and
milling machine
1, lathes and lathe operations
Lathes are generally considered to be the oldest machine tools . although woodworking lathes were originally developed during the period 1000-1 B.C., metalworking lathes with lead screws were not built until the late 1700s .the most common lathe (figure 2.1) was originally called engine lathe because it was powered with overhead pulleys and belts from nearby engines . today these lathes are set up with individual electric motors.
1)Lathe components
Lathes are equipped with a variety of components and accessories . the basic components of a common lathe are described below.
i)Bed
The bed supports all major components of the lathe. Beds have a large mass and are rigidly built ,usually from gray or nodular cast iron . the top portion of the bed has two ways , with various cross-sections ,that are hardened and machined for wear resistance and dimensional accuracy during use .
ii)Carriage
The carriage ,or carriage assembly ,slides along the ways and consists of an assembly of the cross-slide , tool post ,and apron .the
cutting tool is mounted on the tool post ,usually with a compound rest that swivels for tool positioning and adjustment . the cross-slide moves radially in and out ,controlling the radial position of the cutting tool in operations such as facing. The apron is equipped with mechanisms for both manual and mechanized movement of the carriage and the cross-slide by means of the lead screw .
iii)Headstock
The headstock is fixed to the bed and is equipped with motors , pulleys , and V-belts that supply power to the spindle at various rotational speeds . the speeds can be set through manually-controlled selectors .most headstocks are equipped with a set of gears ,and some have various drives to provide a continuously variable speed range to the spindle. Headstock have a hollow spindle to which workholding devices ,such as chucks and collets ,are attached , and long bars or tubing can be fed through for various turning operations .
iv)Tailstock
The tailstock ,which can slide along the ways and be clamped at any position ,supports the other end of the workpiece . it is equipped with a tailstock center that may be fixed (dead tailstock center) or may be free to rotate with the workpiece (live tailstock center ) . drills and reamers can be mounted on the tailstock quill(a hollow cylindrical part with a tapered hole ) to drill axial holes in the
workpiece.
v)f eed rod and lead screw
the feed rod is powered by a set of gears from the headstock .it rotates during the operation of the lathe and provides movement to the carriage and the cross-slide by means of gears ,a friction clutch , and a keyway along the length of the rod . closing a split nut around the lead screw engages it with the carriage . it is also used for cutting threads accurately.
vi)Workholding devices
Workholding devices are particularly important in machine tools and machining operations .in a lathe , one end of the workpiece is clamped to the spindle by a chuck , collets , face plate , or mandrel.
vii)Accessories
Several devices are available as accessories and attachments for lathes. Among these devices are the following:
Carriage and cross-slide stop with various designs to stop the carriage at a predetermined distance along the bed.
Devices for turning parts with various tapers or radii
Milling , sawing, gear-cutting, and grinding attachments ,and various attachments for boring ,drilling ,and thread cutting .
2)Lathe turning
In a typical turning, the workpiece is clamped by any workholding
devices described. Long and slender parts should be supported by a steady rest and follow rest placed on the bed ,otherwise, the part will deflect under the cutting forces. These rests are usually equipped with three adjustable fingers or rollers , which support the workpiece while allowing it to rotate freely . steady rests are clamped directly on the ways of the lathe , whereas follow rests are clamped on the carriage and travel with it .
The cutting tool ,attached to the tool post , which is driven by the lead screw ,removes material by traveling along the bed , a right-hand tool travels toward the headstock , and a left-hand tool toward the tailstock. Facing cutting are done by moving the tool radially with the cross-slide, and clamping the carriage for better dimensional accuracy. 2,milling machine and milling
Milling includes a number of highly versatile machining operations capable of producing a variety of configurations (figure 2.2) with the use of a milling cutter , a multitoothed cutter that produces a number of chips in one revolution .
1)Milling operations
i)slab milling
in slab milling ,also called peripheral milling , the axis of cutter rotation perpendicular to the workpiece surface to be machined (figure2.2(a)) . the cutter ,generally made of high-speed steel , has a
number of teeth along its circumference, each tooth acting like a single-point cutting tool called a plain mill
ii)face milling
in face milling ,the cutter is mounted on a spindle having an axis of rotation perpendicular to the workpiece surface(figure 2.2(b)) . because of the relative motion between the cutting teeth and the workpiece , a face-milling cutter leaves feed marks on the machined surface similar to those left by turning operations . note that surface roughness of the workpiece depends on insert corner geometry and feed per tooth.
iii)End millng
Flat surfaces as well as various profiles can be produced by end milling . the cutter in end milling is shown in figure 2.2(c) . it has either straight or tapered shanks for smaller and larger cutter sizes , respectively . the cutter usually rotates on an axis perpendicular to the workpiece ,although it can be tilted to machine-tapered surfaces.
In conventional milling ,also called up milling ,the maximum chip thickness is at the end of the cut (figure 2.3(a )). The advantages to conventional milling are that (a ) tooth engagement is not a function of workpiece surface characteristics , and (b) contamination or scale on the surface does not affect tool life . this is the more common method of milling . the cutting process is smooth , provided that the cutter teeth are sharp . however , there may be a necessitating proper
clamping.
In climb milling ,also called down milling ,cutting starts at the surface of the workpiece. Where the chip is at its thickest(figure 2.3(b)) . the advantage is that the downward component of the cutting forces holds the workpiece in place, particularly for slender parts. Because of the resulting high-impact forces when the teeth engage the workpiece , however ,this operation must have a rigid setup, and backlash must be eliminated in the table feed mechanism . climb milling is recommended, in general , for maximum cutter life in using computer numerical controlled (CNC) machine tools.
2)types of milling machine
i)column-and-knee type machines
used for general-purpose milling , column-and-knee type machines are the most common milling machines , the spindle on which the milling cutter is mounted may be horizontal for slab milling , or vertical for face and end milling , boring , and drilling operations . The basic components of these machines are as follows:
A work table ,on which the workpiece is clamped using t-slots .the table moves longitudinally relative to the saddle .
A saddle ,which supports the table and moves in the transverse direction.
A knee , which supports the saddle and gives the table vertical
movement so that the depth of cut can be adjusted.
An overarm in horizontal machines , which is adjustable to accommodate different arbor lengths .
A head, which contains the spindle and cutter holders. In vertical machines , the head may be fixed or it can be vertically adjustable, and it can be swiveled in a vertical plane on the column for cutting tapered surfaces .
ii)bed-type machines
in bed-type machines .the work table is mounted directly on the bed ,which replaces the knee and can move only longitudinally . these milling machines are not as versatile as other types ,but they have great stiffness and are used for high-production work . the spindles may be horizontal or veritical , and of duplex or triplex types—that is ,with two or three spindles ,respectively , for the simultaneous machining of two or three workpiece surfaces.
iii)other types of milling machines
planer-type milling machines, which are similar to bed-type machines , are equipped with several heads and cutters to mill various surfaces. They are used for heavy workpieces and are more efficient than planers when used for similar purposes. Rotary-table machines are similar to vertical milling machines and are equipped with one or more heads for face-milling operations.
Various milling-machine components are being rapidly replaced by computer numerical control machines . these machine tools are versatile and capable of milling ,drilling ,boring , and tapping with repetitive accuracy.
Reading material
1,planting and shaping
Planing is a relatively simple cutting operation by which flat surfaces ,as well as various cross-sections with grooves and notches, are produced along the length of the workpiece. Planing is usually done on large workpieces-as large as 25mx 15m(75ftx 40ft).
In a planer, the workpiece is mounted on a table that travels along a straight path. A horizontal cross-rail , which can be moved vertically along the ways in the column ,is equipped with one or more tool heads . the cutting tools are attached to the heads, and machining is done along a straight path. Because of the reciprocating motion of the workpiece, elapsed noncutting time during the return stroke is significant .
Consequently , these operations are neither efficient nor economical , except for low-quantity production . the efficiency of the operation can be improved by equipping planers with tool holders and tools that cut in both directions of table travel .
In order to prevent tool cutting edges from chipping when they
rub along a workpiece during the return stroke , tools are either tilted away or lifted mechanically or hydraulically . because of the length of the workpiece, it is essential to equip cutting tools with chip breakers . otherwise , the chips produced can be very long , interfering with the operation as well as becoming a safety hazard .
Shaping is used to machine parts , which is much like planing , unless the parts are smaller . cutting by shaping is basically the same as by planing . in a horizontal shaper , the tool travels along a straight path , and the workpiece is stationary . the cutting tool is attached to the tool head , which is mounted on the ram .
The ram has a reciprocating motion . in most machines , cutting is done during the forward movement of the ram (push cut ). But in others ,it is done during the return stroke of the ram (draw cut ). Vertical shapers (slotters) are used to machine notches, keyways , and dies. Because of low production rates , only special-purpose shapers , such as gear shapers , are in common use today .
2,grinding operations and machines
Grinding is carried out with a variety of wheel-workpiece configurations . the selection of a grinding process for a particular application depends on part shape and size , ease of fixturing , and the production rate required .
The basic types of grindings—surface, cylindrical , internal , and
centerless grinding—are described in this section. The relative movement of the wheel may be along the surface of the workpiece (traverse grinding , through feed grinding , cross-feeding ), or it may be radially into the workpiece (plunge grinding ) . surface gringers are comprised the largest percentage of grinders used in industry , followed by bench grinders (usually with two wheels at each end of the spindle ), cylindrical grinders , and tool and cutter grinders . the least common are internal grinders.
Grinding machines are available for various workpiece geometries and sizes . modern grinding machines are computer controlled , with features such as automatic workpiece loading and unloading , clamping , cycling , gaging , dressing , and wheel shaping . grinders can also be equipped with probes and gages for determining the relative position of the wheel and workpiece surfaces as well as with tactile sensing features whereby diamond dressing-tool breakage , if any , can readily be detected during the dressing cycle .
1)surface grinding
surface grinding involves grinding flat surfaces and is one of the most common grinding operations . typically , the workpiece is secured on a magnetic chuck attached to the work table of the grinder . nonmagnetic materials generally are held by vises , special fixtures, vacuum chucks ,or double-sided adhesive tapes.
A straight wheel is mounted on the horizontal spindle of the grinder . traverse grinding occurs as the table reciprocates longitudinally and feeds laterally after each stroke . in plunge grinding , the wheel is moved radially into the workpiece ,as it is grinding
a groove
2). cylindrical grinding
in cylindrical grinding ,also called center-type grinding, the external cylindrical surfaces and shoulders of the workpiece are ground . typical applications include crankshaft bearings , spindles , pins, bearing rings , and rolls for rolling mills .
the rotating cylindrical workpiece reciproca t es laterally along its axis. In grinders used for large and long workpieces , the grinding wheel reciprocates ; called a roll grinder , it is capable of grinding rolls as large as 1.8m (72in) in diameter for rolling mills .
the workpiece in cylindrical grinding is held between centers or in a chuck , or it is mounted on a faceplate in the headstock of the grinder . for straight cylindrical surfaces , the axes of rotation of the wheel and workpiece are parallel. Separate motors drive the wheel and workpiece at different speeds . long workpieces with two or more diameters are also ground on cylindrical grinders . cylindrical grinding can produce shapes (form grinding and plunge grinding) in which the wheel is dressed to the form to be ground.
In universal grinders, both the workpiece and the wheel axes can be moved and swiveled around a horizontal plane , permitting the grinding of tapers and other shapes. These machines are equipped with computer controls , reducing labor and producing parts accurately and repetitively.
3)internal grinding
in internal grinding , a small wheel is used to grind the inside diameter of the part , such as to bushings and bearing races . the workpiece is held a rotating chuck and the wheel rotates at 30000 rpm or higher . internal profiles can also be ground with profile- dressed wheels that move radially into the workpiece . the headstock of internal grinders can be swiveled on a horizontal plane to grind tapered holes .
4)centerless grinding
centerless grinding is a high-production process for continuously grinding cylindrical surfaces in which the workpiece is supported not by centers(hence the term “centerless”) or chucks , but by a blade . typical parts made by centerless grinding are roller bearings , piston pins , engine valves, camshafts, and similar components. This continuous production process requires little operator skill.
In internal centerless grinding , the workpiece is supported between three rolls and is internally ground . typical applications are sleeve-shaped parts and rings.
三年级英语朗读材料 One Hello, boys and girls. I’m Li Yan. I’m 9 years old. I’m a student. This is my new friend, Ann. She is 10 years old. She is from Canada. She is a good student. Two Hi, I’m Sam. I’m six years old. I’m a pupil. I have a happy family. My father is a teacher. My mother is a teacher, too. My sister is Sarah. She’s a pupil, too. She is ten years old. I love my family. Three My name is Mike. I’m a boy. I’m from Canada. Look! This is my family. This is my father. He is tall and thin. He’s a teacher. This is my mother. She is short and thin. She’s a teacher, too. This is my sister. She’s short and fat. She has big eyes. She’s cute. She’s a pupil. Four ’m Sarah. I’m from the USA. Look! This is my new bag. It’s on my desk. My pencil box is in my bag. My chair is under my desk. Oh, where’s my book? It’s in my bag. Five ’m Tom. I’m from the USA. I’m thirteen years old. I’m a student. I like strawberries. I don’t like oranges. My father is a teacher. He is short and fat. He likes bananas. My mother is thin. She likes watermelons. I have a brother. He has big eyes. He’s cute. He likes pears.
Passage 1 There are some very good things about open education. This way of teaching allows the students to grow as people develop their own interests in many subjects. Open education allows students to be responsible for their own education, as they are responsible for what they do in life. Some students do badly in a traditional classroom. The open classroom may allow them to enjoy learning. Some students will be happier in an open education school. They will not have to worry about grades or rules. For students who worry about these things a lot, it is a good idea to be in an open classroom. But many students will not do well in an open classroom. For some students, there are too few rules. These students will do little in school. They will not make good use of open education. Because open education is so different from traditional education, these students may have a problem getting used to making so many choices. For many students it is important to have some rules in the classroom. They worry about the rules even when there are no rules. Even a few rules will help this kind of student. The last point about open education is that some traditional teachers do not like it. Many teachers do not believe in open education. Teachers who want to have an open classroom may have many problems at their schools. You now know what open education is. Some of its good points and bad points have been explained. You may have your own opinion about open education. The writer thinks that open education is a good idea, but only in theory. In actual fact, it may not work very well in a real class or school. The writer believes that most students, but of course not all students, want some structure in their classes. They want to have rules. In some cases, they must be made to study some subjects. Many students are pleased to find subjects they have to study interesting. They would not study those subjects if they did not have to. 1.Open education allows the students to ____. A.grow as the educated B.be responsible for their future C.develop their own interests D.discover subjects outside class 2. Open education may be a good idea for the students who ____. A.enjoy learning B.worry about grades C.do well in a traditional classroom D.are responsible for what they do in life 3. Some students will do little in an open classroom because ____. A.there are too few rules B.they hate activities C.open education is similar to the traditional education D.they worry about the rules 4. Which of the following is NOT mentioned in the passage?____ A.Some traditional teachers do not like it.
《分析化学》阅读材料03 摘自Analytical Chemistry (FECS) ●In the Br?sted-Lowry theory, an acid is a proton donor and a base is a proton acceptor. Each acid is related to its conjugate base and vice versa: Acid = base + proton Therefore, the conjugate base of a strong acid must be a weak base and the conjugate base of a weak acid must be a strong base. Together they form a couple, and an acid without its conjugate base is a meaningless concept. In order to release a proton, the acid must find a base to accept it. In an aqueous solution, the proton, H+, having an extremely small ionic radius, cannot exist as such. It is hydrated, forming the hydronium ion H3O+ and higher hydrates. Thus, an acid-base equilibrium is not a simple dissociation equilibrium, but the result of a proton transfer reaction in which there are at least two reagents and two products. Such a process is also called protolysis. The overall reaction is expressed by: HX + H2O = H3O+ + X-. The overall equilibrium constant is K = [H3O+][X-]/[HX][H2O]. The acid dissociation constant Ka is given by: Ka = K[H2O] = [H3O+][X-]/[HX]. Ka reflects not only the acid strength of HX, but also the base strength of water. This why different acid dissociation constants are observed for the same acid in different solvent. ●Similar proton transfer reactions exist in all solvents possessing proton donor and acceptor properties. Proton transfer reactions are extremely fast. This makes them very suitable for analytical applications and acid-base reactions have found wide use in volumetric methods and other analytical techniques. ●The pH value is a measure for the acidity or basicity of a solution, aqueous or nonaqueous. ●Acid-base indicators are chemical substances with acid-base properties, having different colors in their protonated and deprotonated forms. ● A most important application of acid-base systems is related to the property of such a system to act as a buffer. Many chemical reactions produce protons (in aqueous solutions hydroniums) or hydroxide ions. If these products remain in the system, a corresponding pH change is observed. However, if a buffer is present in the solution it reacts with the liberated hydrogen or hydroxide ions so that only a relative small change of pH occurs. Buffer consist of a mixture of a weak acid and its conjugate base. The most efficient buffer for a given pH consists of a 1:1 ratio of the protonated and deprotonated forms of a weak acid (with pKa = pH). This cannot always be achieved, but if we wish to prepare a solution of a certain pH, we select a weak acid with a pKa value close to the desired pH. Buffer solution resists changes in pH upon adding of strong acids or strong bases. Depending on the relative concentrations of the acid and base forms of the buffer, the system can resist small or large additions of strong acid or base. This buffer capacity is defined as the number of moles of strong acid of base required to change the pH of 1 L of buffer solution by one pH unit. Solutions with high or low pH values, formed as a result of dissolution of large quantities of a strong base or acid, are characterized by a large buffer capacity, although the electrolyte practically consists of only one of the conjugate forms (e.g., HCl or NaOH solutions). ● A general requirement for all volumetric methods is that the titration process is fast and that it proceeds in a definite stoichiometric ratio, the endpoint of the reaction must by easy to detect and the reaction should be specific and not influenced by other constituents of the solution, i.e., there should be no interference. Question: 1. A H3PO4 solution is brought to pH = 7.00 by the addition of NaOH. Calculate the concentration of the various forms of orthophosphate if the total phosphate concentration in buffer is 0.200 mol /L. pKa1 = 2.16, pKa2 = 7.21, pKa3 = 12.32. 2. A buffer solution is prepared from acid, HA, Ka = 5 10-5, and its salt. The concentration of HA in the buffer is 0.25 mol / L. To 100 mL of the buffer added 5.0 mmol of NaOH, and the pH of the resulting solution is 5.60. What was the pH of the original buffer? 3.It is desired to change the pH of 100 mL of 0.100 mol / L HCl from 1.00 to 4.40 by the addition of sodium acetate, CH3COONa3H2O. How much solid sodium acetate salt must be added in grams? Assume no volume change for the solution as the result of the addition. 4.What is the buffer capacity of a solution which is 0.100 mol / L of NH3 and 0.200 of NH4Cl? 5.Calculate the pH of each of the following solution: (a) Water in equilibrium with CO2 of the air; pKa1 = 6.38, pKa2 = 10.25. (b) Water as in part (a) brought to pH = 7.00 with NaOH and allowed to regain equilibrium with CO2. 6. Derive the following expression for the pH at the first stoichiometric point in the titration of a mixture of two weak acid: HA, the stronger, Ka1, concentration C1; HB, the weaker, Ka2, concentration C2: pH = 1/2 (pKa1 + pKa2) – 1/2 lg (C1/C2)
教科版科学二年级上册第二单元材料测试卷 姓名:________ 班级:________ 成绩:________ 小朋友，带上你一段时间的学习成果，一起来做个自我检测吧，相信你一定是最棒的！ 一、选择题 1 . 铁球只能沉在水下面，这是因为它排开的水量（）。 A．特别的小 B．特别的大 C．没有关系 2 . 汽车前挡风玻璃属于（）。 A．透明材料B．半透明材料C．不透明材料 3 . 在检验不同形状的纸抗弯曲能力的时候，下列分析正确的是（）。 A．纸抗弯曲的能力随着纸的厚度增加而减小 B．纸抗弯曲的能力与纸被垫的高度有关 C．纸抗弯曲的能力与纸的形状有关 4 . 下面各种工具不能测量头围的是（）。 A．线绳 B．软尺 C．硬塑料尺 5 . 下列制成物品的主要材料中属于天然材料的是（）。 A．塑料桶B．玻璃杯C．木头椅子 二、判断题 6 . 我们可以用瓶盖和竹签做陀螺。（____）
7 . 火车是人工制造的。（______） 8 . 人类利用材料制造了人工世界，让生活更方便。（______） 9 . 电视机属于自然世界里的物品。（______） 10 . 吸水性是指材料对水的渗透能力与材料的组成有关，与结构无关。（______） 11 . 各种船能浮在水面上的原理是船内都有很大的空间。（_____） 12 . 人类做书的材料始终没有变化。（______） 13 . 可以根据玩具车的特征进行分类。（______） 14 . 绵线的柔韧性比铝线强。（_________） 15 . 垃圾都是无用的、有害的。（_________） 三、连线题 16 . “废物”回收后，分别可以做成哪种物品？ 废作业本铁栏杆 废铁罐平板玻璃 废塑料瓶报纸 废玻璃塑料盆 17 . 判断物品在水中的沉浮情况并用线连起来。 木块 玻璃块浮 泡沫块 铜钥匙 塑料块沉 铁钉
小学四年级英语阅读材料狗狗的故事【五篇】 导读：本文小学四年级英语阅读材料狗狗的故事【五篇】，仅供参考， 如果觉得很不错，欢迎点评和分享。 a. Hi, I'm Emily. On Saturday, my dog Clifford takes me to visit my Grandma. After lunch, the radio says a big storm is coming. 嗨，我是Emily!星期六，我的狗狗Clifford带我去看望奶奶。午 饭后，收音机说一场大暴风雨即将来临。 b. We have to move to a safer place. 我们不得不搬去一个较安全的地方。 c. Now we are safe. But Clifford knows Grandma is worried about her house. 现在我们安全了。但是Clifford知道奶奶在担心她的房子。 d. He hurries back to Grandma's hous e. The storm is too big. Trees are falling down. But it can't stop him. 他匆忙往奶奶家赶。暴风雨太大，树都倒了，但是这并不能阻止他。 e. Grandma's house is in great danger. Clifford has to do something. 奶奶的房子处在极大的危险中，Clifford必须做点什么。 f. First he picks up some trees.
首先，他捡起一些树。 g. Then he puts the trees behind Grandma's house. He covers them with sand. He builds a sand hill to save Grandma's house. 然后，他把树放在奶奶的房子后面，再用沙把树盖住。他堆起了一座沙山来保住奶奶的房子。 h. The storm stops. Grandma and I go back to the house. We are so happy to be together again. 暴风雨停了。我和奶奶回到了家。我们又在一起了，真高兴啊! 【第二篇：狗狗超极大营救】Clifford to the rescue 大红狗来救援 小学四年级英语阅读材料：狗狗超极大营救 a: Hi, I'm Emily. My dog Clifford likes to eat and to play. And he likes to help. 嗨!我叫Emily。我的狗狗Clifford喜欢吃和玩，他还喜欢帮助人。 b: One day, Clifford and I are walking. A car passes us quickly. 有一天，我和Clifford在散步的时候，一辆汽车从我们身旁飞快驶过。 c: A police car comes right behind it. The police are chasing robbers. 一辆警车紧随其后，警察在追强盗。
最牛英语口语培训模式：躺在家里练口语，全程外教一对一，三个月畅谈无阻！ 洛基英语，免费体验全部在线一对一课程：https://www.doczj.com/doc/ee3638698.html,/wenkxd.htm（报名网址）Passage 14 Attention to detail is something everyone can and should do-especially in a tight job market. Bob Crossley, a human-resources expert notices this in the job applications that come cross his desk every day. “It’s amazing how many candidates eliminate themselves,”he says. “Resumes arrive with stains. Some candidates don’t bother to spell the company’s name correctly. Once I see a mistake, I eliminate the candidate, ”Crossley concludes. If they cannot take of these details. “Why should we trust them with a job?” Can we pay too much attention to detail? Perfectionists struggle over little things at the cost of something larger they work toward. “To keep from losing the forest for the trees,”says Charles Garfield, associate professor at the University of California, San Francisco, “we must constantly ask ourselves how the details we’re working on fit into the larger picture they don’t, we should drop them and move to something else.” Garfield compares this process to his work as a computer scientist at NASA. “The Apollo II moon launch was slightly off-course 90 percent of the time,”says Garfield. “But a successful landing was still likely because we knew the exact coordinates of our goal. This allowed us to landing was still likely because we knew the exact coordinates of our goal. This allowed us to make adjustments as necessary.”Knowing where we want to go helps us judge the importance of every task we undertake. Too often we believe what accounts for other’s success is some special secret or a lucky break. But rarely is success so mysterious. Again and again, we see that by doing little things within our grasp well, large rewards follow. 66. According to the passage, some job applicants were rejected________ A) because of their carelessness as shown in their failure to present a clean copy of a resume B) because of their inadequate education as shown in their poor spelling in writing a resume C) because they failed to give a detailed description of their background in their applications D) because they eliminated their names from the applicants list themselves 67. The word “perfectionists”(Line 1, Para 3)refers to those who________ A) demand others to get everything absolutely right B) know how to adjust their goals according to the circumstances C) pay too much attention to details only to lose their major objectives D) are capable of achieving perfect results in whatever they do 68. Which of the following is the author’s advice to the reader? A) Although too much attention to details may be costly, they should not be overlooked B) Don’t forget details when drawing pictures
计算机专业英语阅读材料 计算机英语（1） Desktop Pattern In the graphical user interface of Microsoft Windows 98,a graphical pattern-called wallpaper-displayed on the desktop (the background "beneath" windows, icons, and dialog boxes). The pattern or picture in the screen background that can be chosen by the user. To change the desktop pattern, choose Display from the Control Panel. 桌面图案 在Microsoft Windows 98的图形用户界面中,一种显示在桌面上称为壁纸(Wallpaper )的图形图案(窗口、图标和对话框后面的背景),屏幕背景可由用户选择图案样式或画面。要改变桌面图案时,从控制面板上选择显示方式。 计算机英语（2） Federated Database In scientific networking ,a collaborative database (part of a collaborator) in which scientists pool their knowledge and discoveries .Federated databases are one proposed solution to the Grand Challenges——problems that are so complex that they far outstrip the capabilities of individual scientists ,or even individual research institutions ,to tackle them independently. 联合式数据库 在科学联网中,科学家们汇集其知识和发现的一种合作数据库(合作的一部分)。联合数据库是对种种重大挑战问题(Grand Challenges)的一种建议性的解决方案——这些问题太复杂,以致于超出单个科学家的能力,甚至单个研究所都无法来单独解决它们。 计算机英语（3） Collapse When creating an outline or viewing a directory tree (such as in the Windows Explorer ),the process of hiding all the outline levels or subdirectories below the selected outline heading or directory. 折叠 当生成一个题纲或观察一个目录树(如在Windows资源管理器中)时,在选定的题纲标题或目录下隐藏所有的题纲层或子目录的过程。 计算机英语（4） Collision In local area networks (LANs) ,a garbled transmission that results when two or more workstations transmit to the same network cable at exactly the same time . Networks have means of preventing collisions. 冲突 在局域网(LANs)中,当两个或多个工作站恰好在同时向同一个网络线路上传送(数据)时产生的错乱传输。网络拥
《第1课巴黎和会》课外阅读材料 ▲听到停战的消息，巴黎街头人们欣喜若狂。法国总理克里孟梭说：”吻我的姑娘有500多个了。“ ★停战后德军回到柏林，市民热烈欢迎。内心的喜悦洋溢在士兵和姑娘的脸上。 ■会议延续了5个多月，但全体会议仅召开了7次，其他时间多是在大国的秘密会议私下磋商中度过的，据统计，四大国（英、美、法、意）的秘密会议开了145次。以至于在无休止的秘密会议期间，大部分代表无事可做，游览巴黎以打发时间。 ▲和会三巨头都带着各自国家的特色前去谈判：威尔逊带着美国的仁慈，确信美国的方式是最好的，……克雷孟梭则带着法国深沉的爱国精神，胜利的安慰以及对德国复兴永远的忧惧。劳合乔治则关心英国的殖民地及强大的海军，每个人代表国家的利益，同时也代表个人。——《大国的博弈》思考：“美国的方式”是什么？法国的“爱国”如何体现？英国关心的是什么？ ★巴黎和会上，英国、法国、美国、日本等主要的战胜国提出了哪些要求？其出发点是什么？ 法国：收复失地，削弱甚至肢解德国，以确立自己在欧洲大陆的霸权。法国的打算比较集中和单一，围绕严厉制裁和防范德国展开。 英国：采取传统的“大陆均势”政策，保持和加强海上霸权。英国由于利益分布广泛，意图比较复杂。 美国：以“十四点原则”逐步实现其统治世界的野心。美国最为跃跃欲试，想法颇多。战争成就了美国经济，也刺激了美国的政治野心。 日本：攫取德国在山东的全部权益，并占领战前德国在太平洋上控制的岛屿。日本的图谋比较现实和具体，它对欧洲的争夺没有胃口， ■凡尔赛宫见证了法国和欧洲的近代许多重大历史事件，而与巴黎和会巧合的是40多年前就在这里，德国人在普法战争中击败法国人之后，在法国人的皇宫里举行了德意志帝国统一的仪式，这对法国人来说是一件巨大的耻辱事件。40多年后的今天法国人仍然选择在这里，举行战败国──德国签署带有屈辱性质的《凡尔赛和约》的签字仪式。算是法国人对那场战争失败的雪耻。 ▲巴黎和会上的“巧合”与刻意安排： ◇举办和会的地点——凡尔赛宫 ◇《凡尔赛和约》签字的地点——凡尔赛宫镜厅 ◇会议正式召开的时间——1919年1月18日 ◇会议结束和签字的时间——1919年6月28日
2019-2020年小学四年级英语课外阅读计划 一、指导思想 以《英语课程标准》和新教育理论为行动指南，全面落实市教研室英语课外阅读指导意见，初步构建课外阅读课程，让阅读成为学生日常的生活方式。通过英语课外阅读，不断丰富学生的阅历，开拓学生的文化视野，体验学习英语的乐趣，树立学好英语的自信心，实现学习英语的真正意义和价值，为未来的学习奠定坚实的基础。 二、课外阅读活动的实施 1. 周密计划建立“漂流”机制 英语课外读本作为学校的图书资料，由专人负责，并设立图书漂流记载本。一个月左右漂流一次，每班由两个学生负责班级图书的借阅、登记、回收和保管整理工作。 四年级起以班级为单位进行图书漂流活动，学生人手一册书，以班级为单位进行漂流。从各个年级的1班起漂，向同年级的其他班级漂流。每生每月平均阅读1本书，每天阅读20分钟左右。如：《朗文小学英语分级阅读》每册共4个单元，要求学生每周阅读一个单元。每个年级课外阅读时间最好统一，以便教师辅导与检查，阅读也可以作为家庭作业的一部分。 2. 确保时间提高“阅读”效率 学生每天都要有至少20分钟的阅读时间，每周一个中午按漂流计划进行《牛津故事乐园》或《朗文分级阅读》的教师指导阅读活动，利用家作布置学生自读，每周的英语社团活动进行英语课外阅读的辅导。让学生自由阅读，自由笔记，摘录好词佳句，仿写经典语句等。 3. 授之以渔使学生“会阅读” 教师在对学生进行课外阅读指导时，应讲授阅读方法。（1）阅读与朗读结合。（2）阅读教学与听、说、读、写结合。（3）阅读与工具书使用的结合。 4. 多元评价促进学生发展 对学生阅读的篇目每周进行统计，对中高年级的阅读笔记经常检查。结合平时的展示活动对学生的课外阅读进行多元评价。可以采取师生评价、生生评价、教师评价与家长评价相结合：制作一份阅读评价表——《我的一周阅读记录单》，请家长合作，对学生一周的阅读情况进行周评，对表现
Passage 1 Exchange a glance with someone, then look away. Do you realize that you have made a statement? This type of stare often produces hostile feelings. 1. It can be inferred from the first paragraph that___. A) every glance has its significance 2. If you want to be left alone on an elevator, the best thing to do is___. B) to avoid eye contact with other passengers 3. By "a dimming of the lights" (Line 13,Para.1 )Erving Goffman means___. C) ceasing to glance at others 4. If one is looked at by a stranger for too long, he tends to feel___. B) uneasy 5. The passage mainly discusses___. D) the role of eye contact in interpersonal communication. Passage 2 Geraldo Rivera is well known for his compassionate investigative reports on WABC-TV Eyewitness News. But I’m not just in the business of making people cry. I’m in the business of chang e.” 6. Geraldo Rivera is working as a(n)______. B. investigative reporter for a special TV program 7. How many awards did Rivera receive for his work? D. Five 8. Rivera’s inves tigation and expose on the conditions at WillowbrookStateSchool led to _____. D. all of the above
材料科学与工程专业英语第三版翻译以及答案 Document serial number【KK89K-LLS98YT-SS8CB-SSUT-SST108】
UNIT 1 一、材料根深蒂固于我们生活的程度可能远远的超过了我们的想象，交通、装修、制衣、通信、娱乐（recreation）和食品生产，事实上（virtually），我们生活中的方方面面或多或少受到了材料的影响。历史上，社会的发展和进步和生产材料的能力以及操纵材料来实现他们的需求密切（intimately）相关，事实上，早期的文明就是通过材料发展的能力来命名的（石器时代、青铜时代、铁器时代）。 二、早期的人类仅仅使用（access）了非常有限数量的材料，比如自然的石头、木头、粘土（clay）、兽皮等等。随着时间的发展，通过使用技术来生产获得的材料比自然的材料具有更加优秀的性能。这些性材料包括了陶瓷（pottery）以及各种各样的金属，而且他们还发现通过添加其他物质和改变加热温度可以改变材料的性能。此时，材料的应用（utilization）完全就是一个选择的过程，也就是说，在一系列有限的材料中，根据材料的优点来选择最合适的材料，直到最近的时间内，科学家才理解了材料的基本结构以及它们的性能的关系。在过去的100年间对这些知识的获得，使对材料性质的研究变得非常时髦起来。因此，为了满足我们现代而且复杂的社会，成千上万具有不同性质的材料被研发出来，包括了金属、塑料、玻璃和纤维。 三、由于很多新的技术的发展，使我们获得了合适的材料并且使得我们的存在变得更为舒适。对一种材料性质的理解的进步往往是技术的发展的先兆，例如：如果没有合适并且没有不昂贵的钢材，或者没有其他可以替代（substitute）的东西，汽车就不可能被生产，在现代、复杂的（sophisticated）电子设备依赖于半导体（semiconducting）材料四、有时，将材料科学与工程划分为材料科学和材料工程这两个副学科（subdiscipline）是非常有用的，严格的来说，材料科学是研究材料的性能以及结构的关系，与此相反，材料工程则是基于材料结构和性能的关系，来设计和生产具有预定性