ENGLISH 麻生希影视资源The force of gravity acts only in one directionvertically, so that the main force of hoisting and handling machinery which opposes gravity must also act vertically, while the horizontal movement of objects may be accomplished by simply overcoming the friction between them and the surfaces on which they move. This is seen in practice. A force of a hundred pounds may move a loaded truck, which it would require tons to lift; hence the horizontal movements of material may be easily accomplished by hand with the aid of trucks and rollers, so long as it is moved on level planes; but if a weight has to be raised even a single inch by reason of irregularity in floors, the difference between overcoming frictional contact and opposing gravity is at once apparent.Once I enjoyed the pleasure of partaking of such a "dinner," as the guest of Professor and Mrs. Noyons. The company was very mixed, and men who never in their lives had ever done anything else but spoiling their eyes for the sake of science, by reading all manner of ancient manuscripts, were now busy, dressed in a blue apron, stirring the soup and mashing potatoes or vegetables. The menu comprised nothing but potatoes, a little vegetables, and a finely calculated piece of meat.I roamed about aimlessly in a scorching heat. Whither? I did not know myself. I did not know Louvain and met nobody whom I might ask something. I came near a couple of streets that were only ruins; the walls collapsed against each other and filled the roadway with rubbish, so that sometimes I could not see whether I walked on or beside the place where the houses used to stand.
It is a simple affair, this putting up one's hands, but even at such a moment a free citizen has a strong objection against being compelled to this by others, who are no more than one's self, who ask it without any right, except the might derived from the weapon in their hands.At Fort Pontisse or Lierce they seemed to have noticed that the factory was a station for observation. As the officer was still thinking about my case, one of those infernal monster shells crashed down among a group of soldiers, only some yards away. Those who were not hit ran away, but they came back soon, and took up seven or eight comrades, whom they carried into the factory. I shuddered when I saw what had happened, and through the shock the sight gave me I involuntarily jerked my arms.
When De Tijd sent me to Belgium as its correspondent, I had not the faintest notion practically how to perform my duties, for the simple reason that I could not apprehend at all how a modern war might be conducted. But I was destined to receive my first impressions when still on Netherland territory and after my arrival at Maastricht.Seventh.There is no waste of power by slipping belts or other frictional contrivances to graduate motion; and finally, there is no machinery to be kept in motion when the hammer is not at work.
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Outside Cherath a motor-car stood between some partially removed trees. Two officers and three soldiers stood around a map which they had laid on the ground, and with them was a young girl, scarcely twenty years old. She was weeping, and pointed out something on the map, obviously compelled to give information. One of the officers stopped me, was clearly quite satisfied with my papers, but told me that I was not allowed to go on without a permit from the military command. Then I pulled out of my pocket, as if of great importance, the scrap of paper which the commanding officer at the bridge near Lixhe had given me. The other had scarcely seen the German letters and German stamp when he nodded his head approvingly, and quickly I put the thing back, so that he might not notice that I was allowed only to go to Vis.
I started on my return journey to The Netherlands sick to death. The consequences of lying on that wet floor made themselves badly felt, and besides being quite stiff and chilly, my interior was badly out of order.A proof of this last proposition is found in the fact that a thorough latheman will perform nearly as much work and do it as well on an old English lathe with plain screw feed, as can be performed on the more complicated lathes of modern construction; but as economy of skill is sometimes an equal or greater object than a saving of manual labour, estimates of tool capacity should be made accordingly. The main points of a lathe, such as may most readily affect its performance, are firsttruth in the bearings of the running spindle which communicates a duplicate of its shape to pieces that are turned,second, coincidence between the line of the spindle and the movement of the carriage,third, a cross feed of the tool at a true right angle to the spindle and carriage movement,fourth, durability of wearing surfaces, especially the spindle bearings and sliding ways. To these may be added many other points, such as the truth of feeding screws, rigidity of frames, and so on, but such requirements are obvious.
5. Every part laid down has something to govern it that may be termed a "base"some condition of function or position which, if understood, will suggest size, shape, and relation to other parts. By searching after a base for each and every part and detail, the draughtsman proceeds upon a regular system, continually maintaining a test of what is done. Every wheel, shaft, screw or piece of framing should be made with a clear view of the functions it has to fill, and there are, as before said, always reasons why such parts should be of a certain size, have such a speed of movement, or a certain amount of bearing surface, and so on. These reasons or conditions may be classed as expedient, important, or essential, and must be estimated accordingly. As claimed at the beginning, the designs of machines can only in a limited degree be determined by mathematical data. Leaving out all considerations of machine operation with which books have scarcely attempted to deal, we have only to refer to the element of strains to verify the general truth of the proposition.In practice this difference of effect on the top and bottom, or between the anvil and hammer sides of a piece, is much greater than would be supposed. The yielding of the soft metal on the top cushions the blow and protects the under side from the force. The effect produced by a blow struck upon hot iron cannot be estimated by the force of the blow; it requires, to use a technical term, a certain amount of force to "start" the iron, and anything less than this force has but little effect in moving the particles and changing the form of a piece.There was a little more order in the whole district round Lige, since the Germans behaved more decently, and provisions had arrived. The shock, which the burning and butchering of so many places and persons gave to the whole world, had also influenced the conduct of the Germans, and from the beginning of September they made a practice of asking each time when they thought that they had behaved decently: "Well, are we such barbarians as the world calls us?"
These are but a few of many influences which tend to irregular cooling, and are described with a view of giving a clue from which other causes may be traced out. The want of uniformity in sections which tends to irregular cooling can often be avoided without much loss by a disposition of the metal with reference to cooling strains. This, so far as the extra metal required to give uniformity to or to balance the different sides of a casting, is a waste which engineers are sometimes loth to consent to, and often neglect in designs for moulded parts; yet, as before said, the difficulty of irregular cooling can in a great degree be counteracted by a proper distribution of the metal, without wasting, if the matter is properly understood. No one is prepared to make designs for castings who has not studied the subject of cooling strains as thoroughly as possible, from practical examples as well as by theoretical deductions.
Netherland soldiers and inhabitants of the village bustled about along the opposite river-bank. I shouted as loudly as possible; and when at last I succeeded in drawing their attention, I made them understand that I wanted to be pulled across in the little boat, which in ordinary times served as a ferry. A short consultation took place now on the opposite side, after which a soldier, who clearly possessed a strong voice, came as near as possible to the waterside and, making a trumpet of his two hands, roared:"What do you want with him?"
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