1、翻译部分英文原文Underground lighting in coal minesSummaryThe importance of lighting below ground is emphasized and the difficulties associated therewith are outlined. Inadequate or inferior lighting produces nystagmus, and mention is made of the decline in the incidence of new cases since better lighting ha
2、s been introduced.Changes in portable lamps, with improvements in technique and to suit alterations in mining methods, are reviewed, and descriptions of typical modern equipment and methods of application are included. The importance of photometry in lamp-room practice is discussed.Bulbs and cables
3、for miners lamps are considered, and improvements which have been effected in the last few years are indicated.The desirability of extending the use of mains lighting below ground for both the roadways and the coal faces is indicated. Progress in this field is reviewed, together with descriptions of
4、 equipment and results obtained. It is pointed out that the economic aspect of the general introduction of mains lighting to coal faces will be an important factor. Developments are hindered by restrictions in the use of aluminium alloys in coal mines.1 IntroductionThe importance of lighting in mine
5、sNo single factor is of more importance to the mining industry than lighting. Under natural conditions it is always dark below ground, and all light must be produced artificially. Furthermore, mining is a hazardous calling requiring a continual state of awareness and an ability to recognize danger f
6、rom many sources, which is impossible without adequate illumination. A man can work efficiently and give satisfactory results only if he can see what he is doing and is not hampered by inadequate illumination or annoying shadows.Lighting has a serious effect upon morale and plays an important part i
7、n improving operating conditions below ground. In these days of shortage of man-power in the mining industry it is essential that everything should be done to encourage new entrants and to retain those workers already employed; in this respect good lighting underground can have a marked effect.Despi
8、te the recognition of the necessity for adequate illumina- tion in mines, particularly at working places, little attention was devoted to provision of suitable lighting for a number of years. In the past, emphasis was generally laid upon the economic factors involved, and lamps were operated as chea
9、ply as possible. To-day, however, while the necessity for economy is still recog- nized, more attention is rightly devoted to the performance of lamps and to their satisfactory maintenance. This development is timely, because increased mechanization in coal mines requires greater attention to detail
10、 and demands improved lighting standards if full benefit is to be obtained from the machinery employed and the accident hazard is to be reduced to a minimum.The provision of lighting below groundSpecial problems associated with underground lighting have prevented the adoption of orthodox systems, an
11、d have made it impossible to achieve comparable standards of illumination.The main difficulty arises from the presence below ground of inflammable gas, which requires all the lamps and fittings used to be specially designed to eliminate the risk of ignition. Such design features frequently affect th
12、e weight and bulk of the equipment and may prohibit the general use of mains-fed equip- ment. The second important obstacle is the nature of the surface surrounding the working places. In their natural states these are dark in colour and are highly absorbent to the light falling upon them. Coal abso
13、rbs about 95 % of the incident light, shale and carboniferous rocks, about 75%; and props, etc., about 85%, compared with some 40% absorbed by whitewashed surfaces. Much can be done by whitewashing in roadways and permanent situations, but at the coal-face, which is continually moving forward, such
14、expedients are not practicable.The problem is also aggravated by the restricted and con- gested nature of the working places. The roadways comprise comparatively narrow tunnels which are not easy to illuminate without glare. Coal-faces are frequently low in height and the presence of machinery and r
15、oof supports, all of which cast shadows, make even illumination virtually impossible. The only solution here appears to lie in the use of larger light sources, but the avoidance of undesirable extremes of light and dark and of glare is difficult, and the best result can be obtained only by compromis
16、e.2 Visibility in minesIt has become apparent in the last few years that the peculiar requirements of lighting in mines demand a new approach to the problems involved. Investigators in various countries are now devoting themselves to the problems of visibility, including glare. Attempts are being made to assess the illumination level required for efficient performance of the various tasks below ground and to compare these values with those reasona
