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Photomechanics for Gravure





Photomechanics for gravure often appear to the beginner to be complex and a little confusing. But if you keep firmly in mind what functions photomechanics have in the production of gravure image-carriers, you will not find the subject too difficult. You want to remember that gravure can obtain tonal reproductions either bу depositing ink films of varying thickness in different areas of the printed image or by varying the size of intaglio halftone dots, or, finally, by combining both techniques. Technically, this is achieved either by varying the depth of cells, or by varying the area of cells, or by varying both cell depth and area.

Close control of both depth and area of gravure cells is therefore essential for all gravure methods. Treating the image carrier with an etchant removes the required amounts of metal where it should be removed and thereby produces the gravure cells. Photomechanics provide the guide and control for the etching operation. Both the cell areas and their depth can be decisively influenced by the photomechanical image which is either formed on the surface of the image carrier or transferred to this surface after having been formed independently.

We distinguish two kinds of photomechanical images: stencils and continuous photomechanical layers of varying hardnesses and thicknesses. Stencils serve for the making of intaglio halftone image carriers, whereas images of varying hardness and thickness serve as resists in the etching of gravure cells of varying depth.

A firm grasp of the difference between these two photomechanical products is a prerequisite for the understanding of photomechanics for gravure. In photomechanical stencils, the light-sensitive coating is either completely hardened or not hardened at all, with no significant variations between these two extremes. During development of the photoprinted coating, all hardened areas remain on the supporting surface and all unhardened areas are washed away.

In continuous photomechanical layers of varying hardness and thickness, the light-sensitive coating is variably hardened throughout and changed in its solubility to various degrees in various areas. In some areas the coating is harder; in others it is less so. After development, such a coating still presents a continuous uninterrupted film, but it is a film of varying hardness and thickness. The hardness and thickness variations of this film depend on the amount of light to which a given area is exposed; areas exposed to more light are more hardened than areas exposed to less light. These variations in the physical properties of the resist influence the extend to which a given etchant can pass though it or permeate and etch the metal underneath.

The hardness and thickness of the developed photomechanical coating plays a decisive role in the etching of gravure image carriers with cells of varying depth. As a simplified generalizations, it can be said that the depth of cells is inversely related to the hardness and thickness of the photomechanical film. The photomechanical film serves as a resist during the etching of the intaglio image carrier. In gravure methods the resist protects various metal areas not uniformly but to varying degrees from the etchant, depending on its own hardness and thickness in any given area. The harder and thicker the resist, the more an area is protected from the action of the etchant; the more an area is protected, the less it will be etched. Conversely, the less an area is protected from the etchant the deeper will the cells be etched. The lands, bridges, or posts, as the metal areas between cells are called, must consequently be completely protected, whereas the deep shadows, which require the deepest etched calls, are least protected from the etchant.

 

Lesson 4

Грамматика: Цепочка определений.

Основной текст A: Paper: beneath the surface.

Цепочка определений

Если между артиклем (или другим определителем) и существительным, к которому он относится, стоит несколько существительных, они образуют цепочку определений, а существительное, к которому относится артикль, является по отношению к ним опорным. С него рекомендуется начинать перевод цепочки определений.

ink properties – свойства краски;

the car speed calculation problem – проблема вычисления скорости автомобиля.

Некоторые существительные – определения могут переводиться прилагательными, например:

bar – стержень, magnet – магнит;

bar magnet – стержневой магнит;

machine building industry – машиностроительная промышленность.

Однако подобный способ перевода не всегда возможен, часто такие определения приходится переводить существительными в косвенных падежах или предложными оборотами, при этом целесообразно пользоваться "правилом ряда". Порядок перевода обуславливается смысловыми связями между определениями и определяемым словом. Перевод следует начинать справа налево с последнего существительного, а существительные, стоящие перед ним в роли определения, нужно переводить на русский язык существительными в косвенных падежах (чаще родительном) или предложным оборотом. Например:

1 2 3 3 2 1

products price decrease – уменьшение цен на изделие.

Исходя из контекста, устанавливается связь между определениями,

например: 3 1-2

the electric equipment supply – питание электрооборудования.

В данном случае первое слово (electric) является определением второго (equipment).

Часто в подобную атрибутивную группу слов входят прилагательные, причастия, например:

hard – won freedom – с трудом завоеванная свободa;

stainless steel top cover – верхняя крышка из нержавеющей стали;

fixed contact – неподвижный контакт.

Упражнение 1. Переведите на русский язык:

the control system; the measuring unit; semiconductor industry; measuring equipment; life time; effective life time; power consumption; first-class quality; room temperature; power supply line; normal operation conditions; rubber industry; control desk; print quality; average coating weight; high speed wet-on-wet sheet-fed rotary letterpress printing.

 

Упражнение 2. Проанализируйте и переведите следующие словосочета-ния на русский язык:

the traffic speed; the traffic speed increase; the railway bridge; the railway bridge reconstruction; the London underground; the London underground problem; the thermoelectric generator development; the energy accumulation process; the modern house ventilation facilities; the car speed calculation; the arch bridge construction site; the research program result; the Moscow region newspaper; the temperature limit determination; the household goods store; the steam engine invention; the deep sea current measuring device.

Упражнение 3. Переведите на русский язык следующие словосочетания:

internal combustion engine; George Washington Bridge bus terminal station; current events; cylinder wall; English Channel coast; supersonic vertical take-off bomber; fourteen bird and animal stories and plays; wooden house advantages; automatic flight control equipment; essential research programme; beginning college student; improved traffic flow; free school bus service; two-page story; two-bed hotel room, life-long hobby; class words and expressions; federal highway office; Dynamo versus Spartak football match; National Coal Research Institute; Electronic Research and Engineering Laboratory.

Vocabulary Notes

 

Задание. Переведите следующие предложения.

1. rags – тряпьё, ветошь

At first paper industry relied on the use of rags.

2. linen – льняная ткань

In the West it was linen that was used for papermaking until the mid-1800s.

3. cotton – хлопок

Cotton was introduced later for papermaking.

4. to treat – обрабатывать

Both linen and cotton were treated to turn them into papermaking fibre.

treatment – обработка

Linen and cotton were used for papermaking because of minimum treatment required.

5. fibre – волокно

Developments of non-cellulosic fibre from plastic are already on the market.

6. pulp – древесная масса; волокнистая масса, целлюлоза

Different techniques are used for making pulps of woods.

7. softwood – мягкая древесина

Spruce and pine are considered to be softwoods.

8. hardwood – твердая древесина

Hardwoods are reaching the limit of their present economic exploitation.

9. binder – связующее вещество; слой; покрытие бумаги

Lignin is a binder for forming a matrix of fibres.

10. damage – ущерб, повреждение

Damage to the fibre results in a weakened fibre.

11. to weaken – ослаблять

Weakening the fibre is not taken into account with mechanical pulp.

12. bark – кора

The tree is ground after bark removal.

13. to grind (ground, ground) – перемалывать

For making mechanical pulp the tree is ground to produce small chips of wood.

14. resin – смола

Small chips of wood contain all the lignin and resins after mechanical treatment.

15. formation (of paper) – направление волокна

Formation of paper means the distribution of fibres.

16. density – плотность

The thickness of the fibre cell wall is related to the sheet density.

17. bulk – объем; пухлость, рыхлость (бумаги)

The hardwood pulps improve bulk.

18. opacity – непрозрачность

Filters increase the opacity of the paper.

19. absorbency – впитываемость

The hardwood pulps give better absorbency to paper.

20. tear – сопротивление бумаги надрыву

Thicker walled fibres give high tear.

21. tensile – растяжимый; растяжение

Lower tensile is due to thicker walled fibres.

22. burst – сопротивление (бумаги) продавливанию; разрыв кромки

The thickness of the fibre cell affects burst of paper.

23. smoothness – гладкость

Smoothness, whiteness and gloss may affect print quality.

24. beating – размол бумажной массы

Sulphate pulps require more beating than sulphite pulps.

25. acid – кислота

Sulphite process is an acid system.

26. alkaline – щелочной

Sulphate process is an alkaline system.

27. to alter – изменять

The quality of pulp can be altered in sulphite process.

alteration – изменение

Alteration of the pulping conditions has no influence on the quality of pulp in the sulphate process.

28. shrinkage – усадка (бумажного листа)

Sulphate pulps produce lower shrinkage at the same strength.

29. bleaching – отбеливание; обесцвечивание

Special bleaching chemicals and equipment are used to produce good coloured mechanical pulps.

30. permanence – стойкость (краски)

Mechanical pulps have little permanence.

31. waste paper – макулатура, отходы бумаги

Waste paper is a good fibre source.

32. coated (body stock) paper – мелованная бумага

Better grades of waste paper can be used to make coated papers.

33. impregnation – пропитывание; пропитка

Impregnation of papers is often used to produce laminated surfaces.

 

 

Text 4A

 

Задание. Прочтите текст.

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