2018年12月01日 22:25 来源:石家庄新闻网

169 They came up against the problem to which Riach has since devoted so much attention, that of propeller design. ‘We had thought of getting the theory of the screw-propeller from the marine engineers, and then, by applying our table of air-pressures to their formul?, of designing air-propellers suitable for our uses. But, so far as we could learn, the marine engineers possessed only empirical formul?, and the exact action of the screw propeller, after a century of use, was still very obscure. As we were not in a position to undertake a long series of practical experiments to discover a propeller suitable for our machine, it seemed necessary to obtain such a thorough understanding of the theory of its reactions as would enable us to design them from calculation alone. What at first seemed a simple problem became more complex the longer we studied it. With the machine moving forward, the air flying backward, the propellers turning sidewise, and nothing standing still, it seemed impossible to find a starting point from which to trace the various simultaneous reactions. Contemplation of it was confusing. After long arguments we often found ourselves in the ludicrous position of each having been converted to the other’s side, with no more agreement than when the discussion began.

Mongolfier’s next balloon was spherical, having a capacity of 52,000 cubic feet. It was made from water-proofed linen, and on September 19th, 1783, it made321 an ascent for the palace courtyard at Versailles, taking up as passengers a cock, a sheep, and a duck. A rent at the top of the balloon caused it to descend within eight minutes, and the duck and sheep were found none the worse for being the first living things to leave the earth in a balloon, but the cock, evidently suffering, was thought to have been affected by the rarefaction of the atmosphere at the tremendous height reached—for at that time the general opinion was that the atmosphere did not extend more than four or five miles above the earth’s surface. It transpired later that the sheep had trampled on the cock, causing more solid injury than any that might be inflicted by rarefied air in an eight-minute ascent and descent of a balloon.

‘I attach to this a memorandum of my understanding of some points of detail in order to be sure that it is also the understanding of the Board, and I am, gentlemen, with much respect, your obedient servant, S. P. Langley.’

A certain Henry M. Weaver, who went to see the work of the brothers, writing in a letter which was subsequently read before the Aero Club de France, records that he had a talk in 1905 with the farmer who rented the field in which the Wrights made their flights. ‘On October 5th (1905) he was cutting corn in the next field east, which is higher ground. When he noticed the aeroplane had started on its flight he remarked175 to his helper: “Well, the boys are at it again,” and kept on cutting corn, at the same time keeping an eye on the great white form rushing about its course. “I just kept on shocking corn,” he continued, “until I got down to the fence, and the durned thing was still going round. I thought it would never stop.”’

"We were lucky to receive some outstanding bids, all with the same forward-thinking vision as us. Following an exhaustive assessment period, we were able to determine the host cities and countries that best represented the interests of the sport," he said in a statement.

It was at the conclusion of these experiments of 1903 that the brothers concluded they had obtained sufficient data from their thousands of glides and multitude of calculations to permit of their constructing and making trial of a power-driven machine. The first designs got out provided for a total weight of 600 lbs., which was to include the weight of the motor and the pilot; but on completion it was found that there was a surplus of power from the motor, and thus they had 150 lbs. weight to allow for strengthening wings and other parts.

‘6. That tails, both vertical and horizontal, may with safety be eliminated in gliding and other flying experiments.

Having reached the present stage of advancement in its development, it would seem highly desirable, before laying down the investigation, to obtain conclusive proof of the possibility of free flight, not only because there are excellent reasons to hope for success, but because it marks the end of a definite step toward the attainment of the final goal.

An international team of researchers have identified a gene known to affect the risk for alcohol dependence, and determined many other genes which contribute to the risk to a lesser degree.

Andrews hasn’t appeared in a film in nearly a decade, but has lent her unmistakable voice to other big screen projects over the last decade (such as “Despicable Me 3” and “Shrek Forever After”) and appeared in the Netflix series “Julie’s Greenroom.”

Zhang also served as Director of the Sports Department for the Beijing Organising Committee for the 2008 Summer Olympic Games, and was behind the introduction of the Grassroots Year in 2013, which paved the way for the AFC Grassroots Football Day.

For achieving this flight Joseph Mongolfier received from the King of France a pension of £40, while Stephen was given the Order of St Michael, and a patent of nobility was granted to their father. They were made members of the Legion d’Honneur, and a scientific deputation, of which Faujas de Saint-Fond, who had raised the funds with which Charles’s hydrogen balloon was constructed, presented to Stephen Mongolfier a gold medal struck in honour of his aerial conquest. Since Joseph appears to have had quite as much share in the success as Stephen, the presentation of the medal to one brother only was in questionable taste, unless it was intended to balance Joseph’s pension.

Henson’s proposed flying machine.

An important development in connection with the inspection and testing of aircraft parts, particularly in the case of metal, was the experimental application of X-ray photography, which showed up latent defects, both in the material and in manufacture, which would otherwise have passed unnoticed. This method was also used to test the penetration of glue into the wood on each side of joints, so giving a measure of the strength;312 and for the effect of ‘doping’ the wings, dope being a film (of cellulose acetate dissolved in acetone with other chemicals) applied to the covering of wings and bodies to render the linen taut and weatherproof, besides giving it a smooth surface for the lessening of ‘skin friction’ when passing rapidly through the air.

“We wanted the Karathen to have the voice of a classic British actress, albeit somewhat digitally altered,” explained “Aquaman” producer Peter Safran. “And when we found out Julie was interested and available and excited to do it, casting her was a no-brainer.”

The result handed Junior a 3-0 win on aggregate after their 2-0 victory in the semifinal first leg in Bogota.

‘In looking over our experiments of the past two years, with models and full-size machines, the following points stand out with clearness:—

Owing to the necessity of lightness, the weight of the various elements had to be kept at a minimum, and the factor of safety in construction was therefore exceedingly small, so that the machine as a whole was delicate and frail and incapable of sustaining any unusual strain. This defect was to be corrected in later models by utilising data gathered in future experiments under varied conditions.

Both the engine and the triplane model were exhibited at the first Aeronautical Exhibition held at the Crystal Palace in 1868. The triplane had a supporting surface of 28 sq. ft.; inclusive of engine, boiler, fuel, and water its total weight was under 12 lbs. The engine worked two 21 in. propellers at 600 revolutions per minute, and developed 100 lbs. steam pressure in five minutes, yielding one-third horse-power. Since no free flight was allowed in the Exhibition, owing to danger from fire, the triplane was suspended from a70 wire in the nave of the building, and it was noted that, when running along the wire, the model made a perceptible lift.

The wave of condemnation is far from over for He Jiankui, a Chinese geneticist who claimed to help the first two gene-edited babies in the world.

‘There stood our aerial protégée in all her purity—too delicate, too fragile, too beautiful for this rough world; at least those were my ideas at the time, but little did I think how soon it was to be realised. I soon found, before I had time to introduce the spark, a drooping in the wings, a flagging in all the parts. In less than ten minutes the machine was saturated with wet from a deposit of dew, so that anything like a trial was impossible by night. I did not consider we could get the silk tight and rigid enough. Indeed, the framework altogether was too weak. The steam-engine was the best part. Our want of success was not for want of power or sustaining surface, but for want of proper adaptation of the means to the end of the various parts.’

Let it not be thought that in this comment there is any desire to derogate from the position which Ader should occupy in any study of the pioneers of aeronautical enterprise. If he failed, he failed magnificently, and if he succeeded, then the student of aeronautics does him an injustice and confers on the Brothers Wright an honour which, in spite of the value of their work, they do not deserve. There was one earlier than Ader, Alphonse Penaud, who, in the face of a lesser disappointment than that which Ader must have felt in gazing on the wreckage of his machine, committed suicide; Ader himself, rendered unable to do more, remained content with his achievement, and with the knowledge that he had played a good part in the long search which must eventually end in triumph. Whatever the world might say, he himself was certain that he had achieved flight. This, for him, was perforce enough.

There followed, naturally, a lull in the enthusiasm with which ballooning had been taken up, so far as France was concerned. In Italy, however, Count Zambeccari took up hot-air ballooning, using a spirit lamp to give him buoyancy, and on the first occasion when the balloon car was set on fire Zambeccari let down his passenger by means of the anchor rope, and managed to extinguish the fire while in the air. This reduced the buoyancy of the balloon to such an extent that it fell into the Adriatic and was totally wrecked, Zambeccari being rescued by fishermen. He continued to experiment up to 1812, when he attempted to ascend at Bologna; the spirit in his lamp was upset by the collision of the car with a tree, and the car was again set on fire. Zambeccari jumped from the car when it was over fifty feet above level ground, and was killed. With him the Rozier type of balloon, combining the hydrogen and hot air principles, disappeared; the combination was obviously too dangerous to be practical.

Fung Retailing, a privately owned Hong Kong business, increased its equity holdings in Toys ‘R’ Us Asia to 21 percent by buying 6 percent from the Taj noteholders to become its biggest stockholder.

"Many thanks to China and many thanks to the people of China," said the president shortly before the Chinese Ambassador to Tanzania, Wang Ke, handed over the new library to him.

The applications did not materialise, as was only to be expected in view of the vagueness of the proposals. Colombine did some advertising, and Mr Roebuck expressed himself as unwilling to proceed further in the venture. Henson experimented with models to a certain extent, while Stringfellow looked for funds for the construction of a full-sized monoplane. In November of 1843 he suggested that he and Henson should construct a large model out of their own funds. On Henson’s suggestion Colombine and Marriott were bought out as regards the original patent, and Stringfellow and Henson entered into an agreement and set to work.

Langley Memoir on Mechanical Flight, Smithsonian Institution, Washington.

‘2. That the ratio of drift to lift in well-shaped165 surfaces is less at angles of incidence of 5 degrees to 12 degrees than at an angle of 3 degrees.

These achievements meant a good deal; they proved mechanically propelled flight possible. The difference between them and such experiments as were conducted by Clement Ader, Maxim, and others, lay principally in the fact that these latter either did or did not succeed in rising into the air once, and then, either willingly or by compulsion, gave up the quest, while Langley repeated his experiments and thus attained to actual proof of the possibilities of flight. Like these others, however, he decided in 1896 that he would not138 undertake the construction of a large man-carrying machine. In addition to a multitude of actual duties, which left him practically no time available for original research, he had as an adverse factor fully ten years of disheartening difficulties in connection with his model machines. It was President McKinley who, by requesting Langley to undertake the construction and test of a machine which might finally lead to the development of a flying machine capable of being used in warfare, egged him on to his final experiment. Langley’s acceptance of the offer to construct such a machine is contained in a letter addressed from the Smithsonian Institution on December 12th, 1898, to the Board of Ordnance and Fortification of the United States War Department; this letter is of such interest as to render it worthy of reproduction:—

Francesco Lana, with his ‘aerial ship’ stands as one of the first great exponents of aerostatics; up to the time of the Mongolfier and Charles balloon experiments, aerostatic and aerodynamic research are so inextricably intermingled that it has been thought well to treat of them as one, and thus the work of Lana, Veranzio and his parachute, Guzman’s frauds, and the like, have already been sketched. In connection with Guzman, Hildebrandt states in his Airships Past and Present, a fairly exhaustive treatise on the subject up to 1906, the year of its publication, that there were two inventors—or charlatans—Lorenzo de Guzman and a monk Bartolemeo Laurenzo, the former of whom constructed an unsuccessful airship out of a wooden basket covered with paper, while the latter made certain experiments with a machine of which no description remains. A third de Guzman, some twenty-five years later, announced that he had constructed a flying machine, with which he proposed to fly from a tower to prove his success to the public. The lack of record of any fatal accident overtaking him about that time seems to show that the experiment was not carried out.

‘I was foolish,’ he told those who were with him there. ‘I was flying too low. It was my own fault and it will be a severe lesson to me. I wanted to turn round, and was only five metres from the ground.’ A little after this, he got up from the couch on which he had been placed, and almost immediately collapsed, dying five minutes later.

This machine ran on three wheels before leaving the ground, a central undercarriage wheel being fitted in front, with two more in line with a right angle line drawn through the centre of the engine crank at the rear end of the crank-case. The engine was a 35 horse-power Vee design, water-cooled, with overhead inlet and exhaust valves, and Bosch high-tension magneto ignition. The total weight of the plane in flying order was about 700 lbs.

‘In the meantime an engine was also made for the smaller model, and a wing action tried, but with poor results. The time was mostly devoted to the larger model, and in 1847 a tent was erected on Bala Down, about two miles from Chard, and the model taken up one night by the workmen. The experiments were not so favourable as was expected. The machine could not support itself for any distance, but, when launched off, gradually descended, although the power and surface should have been ample; indeed, according to latest calculations, the thrust should have carried more than three times the weight, for there was a thrust of 5 lbs. from the propellers, and a surface of over 70 square feet to sustain under 30 lbs., but necessary speed was lacking.’