choose writing materials according to the facts. "Materials" are deeds or examples, including truth, and serve for composition.
question 2: what is the material selection of an article? The so-called material selection is the process of identifying and tailoring the materials possessed according to certain writing intentions in the writing of an article. It is carried out on the basis of accumulated materials and has entered the conception stage of the article.
The significance of selecting materials lies in:
① Deepening the writing intention
② Enriching the writing content
Question 3: What is the selection of writing materials (what to write about)
Question 4: What are the basic principles of correctly selecting materials for engineering materials? What are the performance, materials and applicable ways of products?
Question 5: What do you mean by the angle of material selection?
Question 6: Composition Selection: How to choose materials for primary school composition:
1. Be true.
Choosing materials means "looking for something". What are you looking for? Look for real people and things that meet the requirements of the topic in daily study, life and labor. Because only truth can touch you, and only by touching yourself can you touch others. What you write is not necessarily personal experience, but you can also hear and learn from the media, but it must be true! Never make things up, behind closed doors. Write the same title, a girl in my class, about her uncle selling vegetables at dawn and being run over by countless vehicles after being hit by a car. I still remember one sentence: "There is blood in my uncle's convenient bag on the mourning hall. You forget the righteousness of the driver, if you find that you hit someone, you should be sent to the hospital in time, and my uncle may still be saved." Read the above words. The author wrote it with tears. As a teacher, I read it with tears. Before I finished reading it, the whole class was already crying. It's not true. How can I write such a wonderful article?
2. Be novel
The purpose of writing articles is to show others. Everyone likes novel, unique and eclectic things, such as those that are cliche, stereotyped, one-sided, and others are bored at first sight, and no one wants to read them, thus losing the purpose of writing. When someone writes about a classmate, he insists on studying at school despite illness (bringing the virus to his classmates and delaying his treatment, fearing that he is not a good person). ). such an article knows the end at the beginning. who likes to read it? I remember an article written very well: when the school started, a book was published, and the students were afraid to send it to themselves. "I" was even more worried. The result happened to be sent to me, but the teacher didn't give it to me, but gave it to a girl behind me. Afterwards, I learned that the girl was the teacher's daughter. The article was unpretentious and the ending gave people a refreshing feeling-an unknown, conscientious and dedicated one. I think of such a true story: a gold mine was discovered in Seattle, and thousands of people crossed the river to look for gold. A wise man bought a boat. When looking for gold, he didn't necessarily make a fortune. Anyone who wants to look for gold must take a boat. This gold digger made a fortune. Writing is the same as this. Only by advocating innovation and finding another way can he make a difference.
III. Be typical < p Express your writing intention. Some students wrote My Classmate with the intention of expressing their good qualities of being helpful. But the selected materials did not have an eraser for my homework. He generously cut a piece for me with a small knife. I ran out of ink during the exam, and he squeezed me a few drops, and so on. These are all things that often happen in students' study and life at ordinary times. I'm not saying that I can't choose the right material, but I can't say it well. Such a trivial matter is really great and unforgettable. Material selection should be typical, not necessarily an earth-shattering event, but it should be profound and explain the problem.
Fourth, we should try our best to choose what we are familiar with.
Material selection for middle school students' compositions:
In writing, three points are in skills and seven points are in material selection. How to choose materials determines the level and success of the composition. So how should we middle school students choose materials to write our own splendid chapters?
1. I choose familiar materials, never take unfamiliar materials
This is the first writing principle that every student must abide by. Choose familiar materials to write, even if you can't create excellent works, you will at least write decent works. If you are familiar with materials, you will be handy when writing articles. Many students will mistakenly think that the more exotic the materials, the better. Instead of writing what they are familiar with, they will write unfamiliar materials, and the result is often thankless. It is easier to write touching and excellent works by selecting familiar materials in our life. At the same time, we all know that the more familiar materials are in our minds, the clearer the context will be, so that we can use them skillfully and express them in fluent language. A classmate wrote to shake Li Bai's hand, but because his understanding of Li Bai only stays in a few poems he learned, the article rambles. It's irrelevant. Therefore, our students are required to learn to choose familiar materials first when writing.
2. I choose real materials, and never choose false materials.
This is the second writing principle to be observed. The truth of materials refers to "real life" in a strict sense. That is to say, the factual materials in the article should strictly conform to the original appearance or actual situation of objective things. Second, it refers to the "artistic truth" that reflects the truth of life in essence. This means that the factual materials in the article should reflect the true face of life in essence. In order to achieve this goal, it is allowed to treat the events and details as the material of life. >: >
Question 7: What material is CrCu? Copper alloy, containing chromium and copper. Excellent anti-corrosion performance, more expensive! , antistatic, wear-resistant!
question 8: what material is becu? copper-beryllium alloy
copper alloy with beryllium as the main alloying element, also known as beryllium bronze. It is an advanced elastic material with the best performance in copper alloys, and has a series of excellent physical, chemical and mechanical properties, such as high strength, elasticity, hardness, fatigue strength, small elastic hysteresis, corrosion resistance, wear resistance, cold resistance, high conductivity, non-magnetism, and no sparks caused by impact.
classification of beryllium copper
There are two kinds of beryllium bronze: processed beryllium bronze and cast beryllium bronze. Commonly used beryllium bronzes are Cu-2be-.5co-.3si, Cu-2.6be-.5co-.3si, Cu-.5be-2.5co and so on. The beryllium content in processed beryllium bronze is controlled below 2%, and .3% nickel or .3% cobalt is added to domestic beryllium copper. Commonly used beryllium bronzes are: Cu-2BE-.3Ni, Cu-1.9BE-.3Ni-.2Ti, etc. Beryllium bronze is a heat treatment strengthened alloy. The processed beryllium bronze is mainly used as various advanced elastic components, especially those requiring good conductivity, corrosion resistance, wear resistance, cold resistance and non-magnetism, and is widely used as bellows, bellows and microswitches. Cast beryllium bronze is used for explosion-proof tools, various molds, bearings, bearing bushes, shaft sleeves, gears and various electrodes. Beryllium oxide and dust are harmful to human body, so attention should be paid to protection in production and use. Beryllium copper is an alloy with good comprehensive mechanical, physical and chemical properties. After quenching and tempering, it has high strength, elasticity, wear resistance, fatigue resistance and heat resistance. At the same time, beryllium copper also has high electrical conductivity, thermal conductivity, cold resistance and non-magnetism. It has no sparks when hitting, is easy to weld and braze, and has excellent corrosion resistance in the atmosphere, fresh water and seawater. Corrosion resistance of beryllium bronze in seawater: (1.1-1.4)×1-2mm/ year. Corrosion depth: (1.9-13.8)×1-3mm/ year. After corrosion, the strength and elongation have not changed, so it can be kept in recycled water for more than 4 years, and it is an irreplaceable material for submarine cable repeater structure. In sulfuric acid medium: in sulfuric acid with concentration less than 8% (room temperature), the annual corrosion depth is .12-.1175mm, and the corrosion is slightly accelerated when the concentration is more than 8%.
properties and parameters of beryllium copper
beryllium copper is a supersaturated solid solution copper-based alloy, which is a colored alloy with good combination of mechanical properties, physical properties, chemical properties and corrosion resistance. After solution and aging treatment, it has high strength limit, elastic limit, yield limit and fatigue limit equivalent to special steel, and at the same time, it has high electrical conductivity, thermal conductivity, high hardness and wear resistance, high creep resistance and corrosion resistance. Beryllium copper tape is used in micro-motor brushes, mobile phones, batteries and products, and is an indispensable and important industrial material for national economic construction. Parameters: density 8.3g/cm, hardness ≥36-42HRC, conductivity ≥ 18%, IACS tensile strength ≥1mPa, thermal conductivity ≥ 15 W/m K2℃ < P > Usage and performance parameters of beryllium copper < P > High-performance beryllium copper mainly focuses on various working conditions of nonferrous metal low-pressure and gravity casting molds. Through in-depth study on the internal relationship between the failure reason, composition and corrosion resistance of beryllium bronze mold material, a high-performance beryllium bronze mold material with high conductivity (heat), high strength, wear resistance, high temperature resistance, high toughness and corrosion resistance of molten metal was developed, which solved the problems of low pressure of domestic nonferrous metals, easy cracking and wear of gravity casting molds, and significantly improved the mold life, demoulding speed and casting strength. Overcomes the adhesion and erosion of metal slag to the mold; Improve that surface quality of the casting; The production cost is reduced; Make the die life close to the import level. The hardness of high-performance beryllium copper is HRC43, the density is 8.3g/cm3, and the beryllium content is 1.9%-2.15%. It is widely used in plastic injection molding die inserts, die cores, die-casting punches, hot runner cooling systems, heat nozzles, integral cavities of blow molding dies, automobile dies, wear plates, etc.
Question 9: What is pehd, a high-density polyethylene plastic, and its English name? HDPE is a non-polar thermoplastic resin with high crystallinity. The appearance of the original HDPE is milky white, and it is translucent to some extent in the thin cross section. PE has excellent resistance to most domestic and industrial chemicals. Some kinds of chemicals can cause chemical corrosion, such as corrosive oxidant (concentrated nitric acid), aromatic hydrocarbon (xylene) and halogenated hydrocarbon (carbon tetrachloride). The polymer does not absorb moisture and has good water vapor resistance, which can be used for packaging purposes. HDPE has good electrical properties, especially high dielectric strength, which makes it very suitable for wires and cables. Medium to high molecular weight grades have excellent impact resistance, even at normal temperature and even at low temperature of -4F.
PEHD is a kind of thermoplastic polyolefin produced by ethylene polymerization. Although PEHD was introduced in 1956, this plastic has not yet reached the mature level. This universal material is still developing its new uses and markets.
question 1: what is the material of inkstone? ..... There are many kinds of inkstone materials: stone, metal, pottery and wood.
1. Stone inkstone is the most common. With diverse materials, easy production, rich colors and complete styles, it has become the most popular and suitable ink stone for collection. Three of the four famous inkstones (Duanyan, Sheyan and Taoyan) are stone inkstones, and other inkstones are stone inkstones, such as Shuque inkstone, Hongsi inkstone, Yishui inkstone, Songhua inkstone, Xugong inkstone and Nishan inkstone. These stones are characterized by Mohs hardness of 4-6, neither soft nor hard, and fine stone quality, which is also the condition for selecting materials for inkstone.
2. Ceramic inkstones, represented by Chengni inkstones (four famous inkstones) and inkstones made of Qin bricks and Han tiles by the people. Compared with ordinary bricks, it is hard and delicate.
3. Metal inkstones, cast iron or copper, were mostly used by officers and men in harsh environments in ancient times. They were not afraid of falling and were easy to conduct heat. Most of them were double-layered, and it was convenient to put warm charcoal fire in the middle.
4. Wooden inkstones mostly belong to the category of literary play. Mainly made of mahogany (also common hardwood), it is easy to play with and use once in a while.