[外语类试卷]大学英语四级模拟试卷498及答案与解析.doc
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1、大学英语四级模拟试卷 498及答案与解析 一、 Part I Writing (30 minutes) 1 For this part, you are allowed 30 minutes to write a composition on the topic: Statistics of Family Expenses in Shanghai. You should write at least 120 words following the outline given below in Chinese:1根据上图描述该城市家庭支出的变化 2分析产生这些变化的原因 3说明这些变化对个人和社
2、会产生的影响 Statistics of Family Expenses in Shanghai 二、 Part II Reading Comprehension (Skimming and Scanning) (15 minutes) Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions attached to the passage. For questions 1-7, mark: Y (for YES) if the state
3、ment agrees with the information given in the passage; N (for NO) if the statement contradicts the information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 1 Fireworks If you have ever been to an aerial fireworks show at an amusement park, baseball game, F
4、ourth of July celebration or on New Years Eve, then you know that fireworks have a special and beautiful magic all their own-a good show is absolutely amazing! Have you ever wondered how this magic works? What is launched into the sky to make these beautiful displays? In this article, you will learn
5、 all about aerial fireworks. Basic Components Just about everyone in the United States has some personal experience with fireworks, either from Fourth of July or New Years Eve celebrations. For example, you have probably seen both sparklers and firecrackers. It turns out that if you understand these
6、 two pyrotechnic (有关烟火制造术的 ) devices, then you are well on your way to understanding aerial fireworks! The sparkler demonstrates how to get bright, sparkling light from a firework, and the firecracker shows how to create an explosion. Firecrackers have been around for hundreds of years. They consist
7、 of either black powder (also known as gunpowder) or flash powder in a tight paper tube with a fuse to light the powder. Black powder, discussed briefly in How Rocket Engines Work, contains charcoal, sulfur and potassium nitrate. A composition used in a firecracker might have aluminum instead of or
8、in addition to charcoal in order to brighten the explosion. Sparklers are very different from firecrackers. A sparkler burns over a long period of time (up to a minute) and produces extremely bright and showery light. Sparklers are often referred to as “snowball sparklers“ because of the ball of spa
9、rks that surrounds the burning portion of the sparkler. If you look at Patent #3,862,865: Sparkler composition, you can see that a sparkler consists of several different compounds: A fuel An oxidizer Iron or steel powder A binder The fuel is charcoal and sulfur, as in black powder. The binder can be
10、 sugar or starch. Mixed with water, these chemicals form a slurry that can be coated on a wire (by dipping) or poured into a tube. Once it dries, you have a sparkler. When you light it, the sparkler bums from one end to the other (like a cigarette). The fuel and oxidizer are proportioned, along with
11、 the other chemicals, so that the sparkler burns slowly rather than exploding like a firecracker. It is very common for fireworks to contain aluminum, iron, steel, zinc or magnesium dust in order to create bright, shimmering sparks. The metal flakes heat up until they are incandescent and shine brig
12、htly or, at a high enough temperature, actually burn. A variety of chemicals can be added to create colors. See lights and colors for a good explanation of the chemistry and physics of color in fireworks. Aerial Fireworks An aerial firework is normally formed as a shell that consists of four parts:
13、Container-usually pasted paper and string formed into a cylinder Stars-spheres, cubes or cylinders of a sparkler-like composition Bursting charge-firecracker-like charge at the center of the shell Fuseprovides a time delay so the shell explodes at the right altitude The shell is launched from a mort
14、ar. The mortar might be a short, steel pipe with a lifting charge of black powder that explodes in the pipe to launch the shell. When the lifting charge fires to launch the shell, it lights the shells fuse. The shells fuse bums while the shell rises to its correct altitude, and then ignites the burs
15、ting charge so it explodes. Simple shells consist of a paper tube filled with stars and black powder. Stars come in all shapes and sizes, but you can imagine a simple star as something like sparkler compound formed into a ball the size of a pea or a dime. The stars are poured into the tube and then
16、surrounded by black powder. When the fuse bums into the shell, it ignites the bursting charge, causing the shell to explode. The explosion ignites the outside of the stars, which begin to bum with bright showers of sparks. Since the explosion throws the stars in all directions, you get the huge sphe
17、re of sparkling light that is so familiar at fireworks displays. Multibreak Shells. More complicated shells burst in two or three phases. Shells like this are called multibreak shells. They may contain stars of different colors and compositions to create softer or brighter light, more or less sparks
18、, etc. Some shells contain explosives designed to crackle in the sky, or whistles that explode outward with the stars. Multibreak shells may consist of a shell filled with other shells, or they may have multiple sections without using additional shells. The sections of a multibreak shell are ignited
19、 by different fuses. The bursting of one section ignites the next. The shells must be assembled in such a way that each section explodes in sequence to produce a distinct separate effect. The explosives that break the sections apart are called break charges. The pattern that an aerial shell paints i
20、n the sky depends on the arrangement of star pellets (颗粒状物 ) inside the shell. For example, if the pellets are equally spaced in a circle, with black powder inside the circle, you will see an aerial display of smaller star explosions equally spaced in a circle. To create a specific figure in the sky
21、, you create an outline of the figure in star pellets, surround them as a group with a layer of break charge to separate them simultaneously from the rest of the contents of the shell, and place explosive charges inside those pellets to blow them outward into a large figure. Each charge has to be ig
22、nited at exactly the fight time or the whole thing is spoiled. 2 If you understand sparklers and firecrackers, then you are well on your way to understanding aerial fireworks. ( A) Y ( B) N ( C) NG 3 Firecrackers have been around for a short time. ( A) Y ( B) N ( C) NG 4 Firecrackers consist of eith
23、er black powder or flash powder. ( A) Y ( B) N ( C) NG 5 Sparklers are similar to firecrackers. ( A) Y ( B) N ( C) NG 6 A sparkler consists of three different compounds. ( A) Y ( B) N ( C) NG 7 It is very common for fireworks to contain aluminum, iron, steel, zinc or magnesium dust. ( A) Y ( B) N (
24、C) NG 8 An aerial firework is normally formed as a shell. ( A) Y ( B) N ( C) NG 9 Simple shells consist of a paper tube filled with stars and _. 10 Multibreak shells burst in _. 11 The pattern that an aerial shell paints in the sky depends on the arrangement of _. Section A Directions: In this secti
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