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What are polymers, homopolymers and copolymers？ And another name for polymer is ______？
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更多“What are polymers, homopolymer…”相关的问题
The term for synthetic polymers used on soil, rock, and earth in construction.
A．Aramide B．Earthscreens C．Geosynthetics D．Styrofoams
A.Metal
B.Ceramics
C.Composite
D.Polymers
A.metals
B.composites
C.polymers
D.alloys
From industrial beginnings in the 19th century, plastics have struggled through a 120 years of glory, failure, disrepute and suspicion on the slow road to public acceptance. Now, at last, one can positively say that plastics are appreciated and enjoyed for what they are; that they make modern life richer, more comfortable and convenient and also more funny. Plastics are warm materials, sympathetic to the human touch and their transformation into things that come into contact with human beings is entirely appropriate.
The fact that there are plastics antiques comes as a shock to most people. How can a material that seems so essential in the 20th century, and one that is so much associated with cheap disposable products, have a history at all？ It is a young technology, and a great pan of the fun of collecting plastics is that beautiful pieces of historical interest can still be found very cheaply.
What is the text mainly about？
A．The chemical and physical features of plastics.
B．The process of public acceptance of plastic as a modem material.
C．The history of plastics as a modem material.
D．The advantages of plastics to people.
For example: The hardness of ceramics is greater than metals. Thus, the comparison is expressed as ceramics ＞ metals. (2pts)
Thermal expansion: A)
From the above comparison, B) ______ have the lowest CTE and C) ______ have the weakest bonding forces among the aforementioned materials.
What is the minimum value of H(p1,…,pn)=H(P) as P ranges over the set of n-dimensional probability vectors？ Find all P's which achieve the minimum.
Part A
Directions: Read the following texts and answer the questions which accompany them by choosing A, B, C or D. Mark your answers on ANSWER SHEET 1.
The Stone age, the Iron age. Entire epochs have been named for materials. So what to name the decades ahead？ The choice will be tough. Welcome to the age of superstuff. Material science—once the least sexy technology—is bursting with new, practical discoveries led by superconducting ceramics that may revolutionize electronics. But superconductors are just part of the picture; from houses and cars to cook pots and artificial teeth, the world will sometime be made of different stuff. Exotic plastics, glass and ceramics will shape the future just as surely as have genetic engineering and computer science.
The key to the new materials is researchers' increasing ability to manipulate substances at the molecular level. Ceramics, for instance, have long been limited by their brittleness. But by minimizing the microscopic imperfections that cause it, scientists are making far stronger ceramics that still retain such qualities as hardness and heat resistance. Ford Motor Co. now uses ceramic tools to cut steel. A firm called Kyocera has created a line of ceramic scissors and knives that stay sharp for years and never rust or corrode.
A similar transformation has overtaken plastics. High-strength polymers now form. bridges, iceskating rinks and helicopter rotors. And one new plastic that generates electricity when vibrated or pushed is used in electric guitars, touch sensors for robot hands and karate jackets that automatically record each punch and chop. Even plastic litter, which once threatened to permanently blot the landscape, has proved amenable to molecular tinkering. Several manufacturers now make biodegradable forms; some plastic six-pack rings for example, gradually decompose when exposed to sunlight. Researchers are developing ways to make plastics as recyclable as metal or glass. What's more, composites—plastic reinforced with fibres of graphite or other compounds—made the round-the-world flight of the voyager possible and have even been proved in combat:a helmet saved an infantryman's life by deflecting two bullets in the Grenada invasion.
Some advanced materials are old standard with a new twist. The newest fiberoptic cables that carry telephone calls cross-country are made of glass so transparent that a piece of 100 miles thick is clearer than a standard window pane.
But new materials have no impact until they are made into products. And that transition could prove difficult, for switching requires lengthy research and investment. It can be said a firmer handle on how to move to commercialization will determine the success or failure of a country in the coming future.
How many new materials are mentioned in this passage？
A．Two.
B．Three.
C．Four.
D．Five.
What is the outstanding feature of the book H is for Hawk？
A．Beautiful language in the book.
B．Truthful recording of the facts.
C．Miserable and touching story.
D．Enthusiasm conveyed through the book.
In the figure above, what is the value of h？
A．2
B．2.2
C．2.4
D．2.6
E．2.8
What can we guess about the woman who owned the shoe？
A．She must have lived h happy Me.
B．She certainly dropped the shoe on purpose.
C．Her adventurous spirit is definitely admirable.
D．Her other shoes were equally fashionable.
