摘要:

Two categories of quality assessment of foodstuffs by panels of judges may be distinguished. In 'grading', an absolute assessment representative of the generality of consumers is sought. In 'analysis', maximum sensitivity is desirable and emphasis is shifted from absolute to relative assessments. In four series of 'grading' tests, individual ratings were most variable in the quality region close to the lower limit of acceptability, thus increasing to about 30 the calculable size of panel required to distinguish differences of the order of 5% from an assigned standard. The threshold concentration of primary taste substances detectable varies considerably between individuals, but except in extreme cases no consistent relation between taste acuity alone and palatability judgments was indicated. However, the judging characteristics of individuals may be investigated numerically by computing the correlation coefficients and regression equations relating their assessments to the average of those of all other members of the same panels. In this way a range of sensitivity of the order of 40% was demonstrable in the tests under review, making possible an objective evaluation of the suitability of individuals for 'grading' or 'analytical' tests.

ISSN:1923-4287    

DOI:10.1139/cjr46f-024

出版商:NRC Research Press    

年代:1946

数据来源: NRC

摘要:

GradeAlarge eggs had the lowest average solids content (25.6%) of the grades studied and GradeCeggs had the highest (26.6%). The solids content increased during the period from December 1944 to July 1945. The total increase during this interval was about 0.5%.The average potassium chloride value of powder produced from GradesBandCeggs was higher than the value for GradeAmedium eggs; Graded medium and pullet eggs produced powder better in this quality attribute than GradeAlarge (differences of about 2%). The use of GradeCeggs resulted in a powder with an average fluorescence value about 2 units greater than for powder from any other grade of eggs. The month of egg production affected quality measures on the resulting powder. As the season progressed there was a decrease in the fluorescence value and pH and an increase in potassium chloride value and foaming volume value.The changes noted could not be attributed to climatic conditions, but may be attributable to feeding practices and to increased age of the hen.

ISSN:1923-4287    

DOI:10.1139/cjr46f-025

出版商:NRC Research Press    

年代:1946

数据来源: NRC

摘要:

A process is described for the application of dust-laying oil to woollen blankets, in which use is made of a positively charged oil-in-water emulsion. During a commercial-scale trial of this process, difficulty was encountered in the form of a progressive build-up of oil and fatty acid after repeated laundering and oiling. The inclusion in the laundering formula of modified soda in a soap: soda ratio of 3:1 has been found to give satisfactory control of the fatty acid content, and to assist greatly in preventing the accumulation of oil.

ISSN:1923-4287    

DOI:10.1139/cjr46f-026

出版商:NRC Research Press    

年代:1946

数据来源: NRC

摘要:

Three magnifying stereoscopes, intended for orienting stereo pairs of vertical air photographs and then ruling in the directions of the projections of the air bases on the photographs, were designed and constructed in the National Research Laboratories for the Department of Mines and Resources. Some features found useful in previously designed photogrammetric instruments were incorporated.

ISSN:1923-4287    

DOI:10.1139/cjr46f-027

出版商:NRC Research Press    

年代:1946

数据来源: NRC

摘要:

The description is given of an easily constructed dividing head that embodies the circles and other parts of discarded theodolites. Originally designed for facilitating the inspection of munitions gauges, the instrument was found to have other valuable applications in metrology. In the appendix there is an account of the method used to calibrate the graduated circle of one of these "angle-heads", in which angles are read to single seconds of arc.

ISSN:1923-4287    

DOI:10.1139/cjr46f-028

出版商:NRC Research Press    

年代:1946

数据来源: NRC

摘要:

In World War II a shortage of manners' sextants resulted in the collection by the Royal Canadian Navy of used sextants from various sources. These were, as far as possible, reconditioned and verified by the National Research Laboratories, Ottawa. For this work, and for calibrating new sextants, some modifications were made to the collimator system regularly employed for the verification of angle-measuring instruments. A brief description is given of the apparatus and of the procedure developed for testing sextants, together with a few remarks on sextant errors.

ISSN:1923-4287    

DOI:10.1139/cjr46f-029

出版商:NRC Research Press    

年代:1946

数据来源: NRC

摘要:

levo-2,3-Butanediol is more effective than glycerol and less effective than ethylene glycol as a freezing point depressant for water. The considerable discrepancy that is reported between observed freezing points and values calculated from Raoult's law for solutions of these chemicals is attributed to hydration. The antifreeze property oflevo-2,3-butanediol is not impaired by prolonged refluxing or by use in automobile cooling systems. The viscosity of 50 to 60% solutions is considerably greater than that of 50 to 60% ethylene glycol and is slightly greater than that of 50 to 60% glycerol at 20 °C., the differences in viscosity between these solutions being magnified by low temperatures. Kinematic viscosity data are presented forlevo-2,3-butanediol solutions at concentration intervals of 10% over the greater part of the liquid range.The comparatively low surface tension oflevo-2,3-butanediol solutions indicates a possible need for precautionary measures against creeping and foaming. Metallic corrosion is not greater than with water, barring excessive contamination with acetates.levo-2,3-Butanediol and ethylene glycol are judged equally satisfactory with respect to heat capacity, flash point, expansion on solidification and heating, and effects on metal finishes and rubber. Density oflevo-2,3-butanediol solutions cannot be used as a measure of freezing point protection. The mixtures of 2,3-butanediol isomers obtained withAerobacter aerogenes,Aeromonas hydrophila, andBacillus subtilisare lacking in antifreeze properties because of their high content of themeso-isomer.

ISSN:1923-4287    

DOI:10.1139/cjr46f-030

出版商:NRC Research Press    

年代:1946

数据来源: NRC

摘要:

The one-dimensional problem of heat addition in a duct with friction losses is examined.The variation of the total head temperature and pressure ratio, as well as the static ones, have been obtained as functions of the Mach number and the frictional coefficient. It is shown that an extreme value of the total head temperature and pressure ratio is obtained when the Mach number equals unity. An extreme value of the static temperature is obtained at Mach numbers smaller or larger than unity, depending on the form of the duct.It is concluded that when the total head pressure losses are to be kept low, a diverging duct must be used. The frictional losses have a convergence effect on the flow. When the friction losses are disregarded, no total head pressure loss will result if the area variation of the duct is such as to ensure a constant Mach number.The results and conclusions found may be useful in the design of combustion chambers for gas turbines, propulsive ducts, and rockets.

ISSN:1923-4287    

DOI:10.1139/cjr46f-031

出版商:NRC Research Press    

年代:1946

数据来源: NRC