比喻修辞
带钩NIKOLA TESLA
The advances described are the result of my rearch carried on for many years with the chief object of transmitting electrical energy to great distances. The first important practical realization of the efforts was the alternating current power system now in universal u. I then turned my attention to wireless transmission and was fortunate enough to achieve similar success in this fruitful field, my discoveries and inventions being employed throughout the world. In the cour of this work, I mastered the technique of high potentials sufficiently for enabling me to construct and operate, in 1899, a wireless transmitter developing up to twenty million volts. Some time before I contemplated the possibility of transmitting such high tension currents over a narrow beam of radiant energy ionizing the air and rendering it, in measure, conductive. After preliminary laboratory experiments, I made tests on a large scale with the transmitter referred to and a beam of ultra-violet rays of great energy in an attempt to conduct the current to the high rarefied strata of the air and thus create an auroral such as might be utilized for illumination, especially of oceans at night. I found that there was some virtue in the principal but the results did not justify the ho旦开头的成语
pe of important practical applications although, some years later, veral inventors claimed to have produced a "death ray" in this manner. While the published reports to this effect were entirely unfounded, I believe that with the new transmitter to be built, this and many other wonders will be achieved. Much time was devoted by me to the transmission of radiant energy, in various forms, by reflectors and I perfected means for increasing enormously the intensity of the effects, but was baffled in all my efforts to materially reduce dispersion and became fully convinced that this handicap could only be overcome by conveying the power through the medium of small particles projected, at prodigious velocity, from the transmitter. Electro-static repulsion was the only means to this end and apparatus of stupendous force would have to be developed, but granted that sufficient speed and energy could be realized with a single row of minute bodies then there would be no dispersion whatever even at great distance. Since the cross ction of the carriers might be reduced to almost microscopic dimensions an immen concentration of energy, irrespective of distance, could be attained.
When I undertook to carry out this plan in practice, the difficulties emed insurmountable.
In the first place, a clod vacuum tube could not be employed as no window could withstand the force of the impact. This made it absolutely necessary to project the particles in free air which meant that each could hold only an insignificant charge. Thus, no matter how high the potential of the terminal, the force of repulsion would be necessarily too small for the purpo contemplated. . . . But by the application of my discoveries and inventions it is possible to increa the force of repulsion more than a million times and what was heretofore impossible, is rendered easy of accomplishment. The successful carrying out of the plan involves a number of more or less important improvements but the principal among the include the following:
小鲤鱼历险记主题曲歌词
1. A new form of high vacuum tube open to the atmosphere.
2. Provisions for imparting to a minute particle an extremely high charge.
3. A new terminal of relatively small dimensions and enormous potential.
4. An electro-static generator on a new principle and of very great power.
FIG. 1
ILLUSTRATING OPEN VACUUM TUBE
花呗临时额度The devices and methods of operation will be explained by reference to the attached drawings in which Fig. 1 and Fig. 2 reprent forms of the new open tube.
In Fig. 1, the device consists of an inner cylindrical conduit 1, cemented to a metallic socket 3, and an outer conduit 2, which is tightly screwed to the socket by a nut 4, and has on the open side a taper with a cylindrical end 9, of the same inside diameter as con
duit 1. The socket 3, is bored out to provide a large chamber around the inner conduit and carries a pipe 7, through which thoroughly desiccated air or other gas under suitable pressure is supplied. The open end of the inner and the tapering part of the outer conduit are ground to form an expanding nozzle 8, through which the air escapes into the atmosphere thereby creating a high vacuum in the inner conduit. The socket 3 has a small central hole and is provided with an inside extension 5, and a threaded outside projection 6, the latter rving for connection to a container supplying automatically suitable particles or material for same while the former fulfill the purpo of charging them as they emerge from the hole. The conduit 1 and 2, may be made of fud quartz, pyrex glass or other refractory material and it is obviously desirable that all the parts of the apparatus have small and nearly equal coefficients of thermal expansion especially when the working medium, which might also be superheated steam,
is at an elevated temperature.
It will be obrved that in this tube I do away with the solid wall or window indispensable in all types heretofore employed, producing the high vacuum required and preventing the
inrush of the air by a gaous jet of high velocity. Evidently, to cure this result, the dynamic pressure of the jet must be at least equal to the external static pressure.
Expresd in symbols:
V2w/2g = P
Assuming equality:
V = √2g P/w
in which equation V is the speed of the jet at its entrance to channel 8 in meters, g the acceleration of gravity likewi in meters, P the external pressure in kilograms per square meter and w the normal weight of the air in kilograms per cubic meter. Now
g = 9.81 meters
P = 10332.9 kilograms
北京市鲁迅中学w = 1.2929 kilograms
The values give
V = 396 meters
FIG. 2
SHOWING A MODIFIED FORM OF OPEN VACUUM TUBE
Some allowance should be made for the frictional loss in the nozzle and the outlet channel and also for the deflection of the jet. For most purpos, the velocity need not be much greater, but as the degree of rarefaction depends on the square of V, it is desirable to obtain as high a value as practicable. Usually, vacuums obtained by a mercury vapor pump are considered very high. In tho, the velocity is only 280 meters per cond but the vapor is 6.9 times heavier than air. Therefore to get the same vacuum in the air jet, its speed should be 280 x [6.9]1/2 = 735 meters. With a working medium at high temperature and pressure, both within practicable limits, this value can b
e attained and even exceeded. Thus, a gaous jet of very high velocity affords a means for closing the end of the tube, more perfectly than any window that can be made while at the same time permitting and facilitating the exit of the particles. Referring to fig. 2., it shows schematically a modified form of my tube intended for various scientific and practical us when it may be preferable or necessary not to discharge the jet through the open end. The construction of the device will be easily understood in view of the foregoing description like parts being similarly designated. A cylindrical conduit 1, is provided as in fig. 1, but the outer cone is replaced by a block 2, of lava or other insulating material shaped as indicated and firmly cemented to the conduit 1, which is hermetically joined by a nut 4, to a metallic plug 3, having a central hole, and extensions 3 and 6, rving the purpo stated above. The working fluid, as compresd desiccated air, is supplied by means of a pipe 7, to a large annular space around conduit 1, and escapes through an expanding nozzle 8, formed by the tapering part of the block and the end of the conduit, into a chamber connected by a pipe 10, to a vacuum pump of large capacity - not shown on the drawing - for carrying off not only the air issuing from the noz
zle but also that rushing in from the outside through the open end 9. In order to minimize the volume of the latter, I avail mylf of an invention of mine known as the "valvular conduit" by providing the wall of the open end 9, with recess as indicated giving ri to whirls and eddies which u up some of the energy of the stream and reduce its velocity. In this way, a pressure of about 100 millimeters of mercury can be readily maintained in the chamber increasing greatly the expansion ration of the air and its speed through the nozzle.
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