摘要:

In ram-jet propulsion, artificial compression before combustion does not exist. Therefore, the only factors which may influence the increase in momentum, i.e., the thrust, are:(1) The degree of initial dynamic compression by a diffuser;(2) The shape of the combustion chamber;(3) The variations of the rate of heat release along the tube;(4) Air excess coefficient;(5) Kind of fuel;(6) Velocity of flight;(7) Aerodynamic and heat losses.This paper deals almost exclusively with the first four factors, i.e., with the theoretical case of an ideal gas and a perfect flow, with no heat or aerodynamic losses involved. The possible appearance of shock waves is disregarded. Neither are boundary layer phenomena discussed in this paper. The external fairing and the relation between the internal and external shape, as well as the influence of this relation on the actually obtainable thrust and efficiency, are also considered to be beyond the scope of the paper. General conclusions are drawn as to the optimum shape of the ideal engine from the standpoint of efficiency. It is found that air should be submitted initially to as high a dynamic compression as possible, i.e., using all kinetic energy available, after which a combustion chamber of constant cross section is used—and finally a nozzle. Another conclusion is that it is impossible to obtain a positive thrust with a combustion chamber of constant cross section, if no dynamic compression, by a diffuser, is initially applied. Special attention is drawn in the paper to the representation and interpretation of the ideal ram-jet cycle on the entropy diagram, this giving a clear picture of the relations between the energy released and the efficiency and thrust obtainable. The fact that in the flow through a tube of constant cross section with heat release (e.g., by combustion), the pressure may decrease even if ideal gas and perfect flow (with no losses involved) are concerned, is emphasized throughout the paper, as it seems that generally this fact is rather overlooked.

ISSN:1923-4287    

DOI:10.1139/cjr48a-029

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

A number of hydrogen and helium lines have been identified as features of the auroral spectrum. The relative intensities of these lines suggest that the excitation process is electron collision. Furthermore, the intensities of the helium lines indicate an "excitation temperature" of 4600°K., and the intensities of the hydrogen lines an "excitation temperature" of 7600°K.

ISSN:1923-4287    

DOI:10.1139/cjr48a-030

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

The slow neutron disintegration of B10yields two groups of α-particles, corresponding to the production of Li7in either the ground state or an excited state. The γ-radiation accompanying the de-excitation of the excited nucleus was studied. Boron in the form of boron trifluoride in a proportional counter was irradiated with slow neutrons from a Ra–α–Be source. Coincidences were counted between α-particle pulses in the proportional counter and γ-ray pulses in an adjacent Geiger–Müller counter. The ratio of the α–γ coincidence rate to, the α-rate gave the product of the efficiency of the Geiger–Müller counter and the number of quanta emitted per boron disintegration. The absorption coefficient of the γ-radiation in lead was measured, and, by comparison with the absorption coefficients for the γ-radiation from Cu64and Au198, the energy was found to be 0.48 ± 0.015 Mev. The quantum efficiency of the Geiger–Müller counter for radiation of this energy was determined by calibration with standard sources of Co60and thorium active deposit. Hence the number of quanta per boron disintegration was found to be 0.90 ± 0.08, in satisfactory agreement with the value to be expected from the relative abundance of the α-particle groups from this reaction.

ISSN:1923-4287    

DOI:10.1139/cjr48a-031

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

In about 70% of the disintegrations, thorium C″ transforms to the ground state of thorium D by the emission of a β-ray and two successive γ-rays of energy 0.58 and 2.62 Mev. A search has been made for a γ-ray of energy 3.20 Mev. which would be emitted if a single radiative transition occurred. Using a source of radiothorium in equilibrium with its decay products, the secondary electrons ejected by the γ-rays from thin radiators of lead and uranium were analyzed in a magnetic lens spectrometer. No photoelectrons ejected by a 3.20 Mev. γ-ray were observed. If the γ-ray occurs its intensity is less than 0.2% of the intensity of the γ-ray at 2.62 Mev. This result is discussed in the light of the proposed disintegration schemes of thorium C″.

ISSN:1923-4287    

DOI:10.1139/cjr48a-032

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

A detailed account is given of experiments carried out to detect an (n,2n) reaction in deuterium. A Po-α-Be neutron source was surrounded by a hollow aluminum sphere 30 cm. in diameter, which could be filled with heavy water. The sphere was surrounded by an effectively infinite medium of paraffin oil. The neutron density distribution outside the sphere was measured with a small boron trifluoride chamber (6 mm. diameter × 20 mm. long). The total integrated densities of neutrons were determined both with the sphere empty and filled with heavy water. After correcting for absorption of thermal neutrons by the heavy water, the aluminum sphere, and the source, and of fast neutrons by the oxygen of the heavy water, it is shown that the fraction of neutrons giving an (n,2n) effect is 0.1 ± 2.7%. This indicates that the effect is less than both that predicted by Höcker's theory (~ 10%) and that reported from an earlier experiment by Halban and coworkers (18%). However it is in good agreement with measurements made by Fenning and Knowles (1.4 ± 5%).

ISSN:1923-4287    

DOI:10.1139/cjr48a-033

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

The fluorescence yields of theLlevels have been computed separately on the basis of radiation widths obtained from the work of Massey and Burhop, the widths of Auger transitions of the Coster–Kronig type measured by Cooper, and existing information on the widths of theLlevels. In the case of fluorescence excitation, the total fluorescence yield calculated in this way is in general agreement with measurements of Lay. In the case of excitation by internal conversion of γ-radiation in theLlevels, it is shown that the total fluorescence yield for elements in the vicinity of tantalum is appreciably less than the yield measured by Lay for fluorescence excitation, but that for the heavier elements near uranium, the yields should be comparable.

ISSN:1923-4287    

DOI:10.1139/cjr48a-034

出版商:NRC Research Press    

年代:1948

数据来源: NRC

摘要:

The amount ofLradiation resulting from theKconversion of γ-radiation emitted in the disintegration of ThB has been measured and found to be in general agreement with the calculations of the preceding paper. This amount, which is determined mainly by the fluorescence yield of theL3level, confirms the results of Küstner and Arends; selective absorption measurements confirm the calculated value for the ratio of the fluorescence yields of theL2andL3levels for the product element (bismuth). The yields ofLradiation resulting from theLconversion of the low energy γ-radiation emitted in the disintegrations of ThC and of RaD have been measured and compared. In the first case the yield is too high, and in the second it is too low compared with the calculated values. Selective absorption measurements indicate that the yields of theL1andL2levels, taken together, are equal to that of theL3level. It is shown that the experimental result for ThC can be explained on the assumption that Auger transitions of the typeL1 → L2Nplay some part in the distribution of energy in the spectrum; the result for RaD, which is consistent with the results of Stahel (1935), indicates that the low energy γ-transitions emitted by that element and converting in theLlevels are excited in less than 100% of the disintegrations.

ISSN:1923-4287    

DOI:10.1139/cjr48a-035

出版商:NRC Research Press    

年代:1948

数据来源: NRC