摘要:

The thermal resistance of a pile fabric uncovered and covered with thin fabrics of various permeabilities was measured under different conditions of wind velocities and wind direction. Wind velocities up to 30 m.p.h. were used and tests were carried out with winds striking the surface of the material at 0°, 30°, 45°, and 90°. The permeabilities of the covers varied between 0 and 193 cu. ft. per sq. ft. per min., under a pressure difference ofin. of water across the fabric. The effects of varying the conditions of the thermal resistance of the boundary air layer are discussed and corrections applied to the results for the resistance of this air layer. The results show that for low wind velocities, the permeability, within wide limits, is relatively of little importance, but with higher wind velocities it is advantageous to employ a covering fabric of as low a permeability as possible.

ISSN:1923-4287    

DOI:10.1139/cjr47a-018

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

The modified Kozeny equation has been found to be satisfactory for the measurement of the specific surface of inorganic pigments having particle diameters of the order of 0.1 to 0.2 µ to within ±10%. These powders were too fine for visual microscope counting or standard sedimentation methods of specific surface measurement. The results obtained from experimental data were checked against those calculated from electron microscope counting for two of the powders studied and found to be in satisfactory agreement.

ISSN:1923-4287    

DOI:10.1139/cjr47a-019

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

A method is described for measuring the radium content of substances in which the radium concentration is of the order of micrograms per gram of material. The gamma-ray activities of the unknown material and of a standard radium capsule are compared by means of Geiger-Müller counters. Corrections for self-absorption and distance are given for rectangular and cylindrical sources. The effect of radiation scattered by the source into the detector is discussed. Synthetic bulk sources made up with known quantities of radium were used for the experimental work.

ISSN:1923-4287    

DOI:10.1139/cjr47a-020

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

The photographic emulsion method of registering the tracks of ionizing particles suffers from certain disadvantages that are mainly due to the relatively large size of grains forming the tracks and their large spacing. These disadvantages are mostly removed in new emulsions that have been prepared after numerous tests. The tracks of ionizing particles in these emulsions consist of grains of diameterd ~ 0.2 µ, which often form continuous lines.Grain spacing is no longer the main cause of apparent straggling, except below a range of 3 to 4 mm. of air. The standard deviation in determining energy from a single measurement of range is 3.25 to 3.5% for protons of 0.6 to 2.4 Mev., and 1.3 to 1.9% for α-rays of 4 to 8.5 Mev. The latter deviation is one-half to one-quarter that obtained in commercial emulsions. Ease of finding the tracks, especially of protons, is considerably increased. The tracks of fission fragments have a characteristic appearance and are easily found amidst the faint or invisible tracks of α-rays and protons. Slow electron tracks have occasionally been seen.The action of certain sensitizing and desensitizing chemicals is described and discussed in terms of the theory of the photographic process.The grain spacing is related to the diameter of the grain, the concentration of silver bromide in the emulsion, and the average probability of development of the grains touched by the ionizing particle. A quantitative theory is given for the probability of development in terms of the specific energy loss and a sensitivity parameter of the emulsion. The observed variation of the grain spacing with residual range of protons, α-rays, and fission fragments can be approximately explained by the theory.

ISSN:1923-4287    

DOI:10.1139/cjr47a-021

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

A direct computational procedure is given for finding the coefficients of the exponential terms in the expressions for the time dependence of the amounts of the various products in a given radioactive series. The method is based on the partition of a matrix which can be written down directly from the diagram of the series. After the explanation of simple applications, an example involving double branching with 10 members of the series is considered in order to exhibit the generality and directness of the method.

ISSN:1923-4287    

DOI:10.1139/cjr47a-022

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

Using a Ra-α-Be source and a small boron trifluoride chamber as detector, the ratio of the neutron absorption cross-sections of boron and hydrogen, σB/σH, has been measured by the integration method in water and in aqueous solutions of boric acid. The result iswith a statistical error of ±30. Subsidiary experiments have been made which fix at about 3% the upper limit of the systematic error caused by perturbation of the neutron density in the neighbourhood of the ionization chamber.

ISSN:1923-4287    

DOI:10.1139/cjr47a-023

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

The asymptotic behaviour of the neutron distribution due to a point source in an infinite homogeneous medium in which a convergent chain reaction (multiplication constantk<1) takes place is investigated without special assumptions about the properties of the medium and the mechanism of neutron diffusion. It is shown under very general assumptions that at large distancesrfrom the point source the neutron distribution always has the formGeneral expressions for the constants μ andAof this asymptotic form of the distribution are given for anyk<1 in terms of the Fourier transform of the spatial distribution of primary fission neutrons. These expressions reduce to particularly simple form for (1 − k) << 1. The exact expression for the neutron distribution throughout the medium is given in integral form. Four special frequently occurring cases are discussed as illustrations of the general result.

ISSN:1923-4287    

DOI:10.1139/cjr47a-024

出版商:NRC Research Press    

年代:1947

数据来源: NRC