Die Erhöhung der Grundfrequenz und der Beullast von Kreisplatten durch geeignete plastische Verformung

Zusammenfassung Eine M?glichkeit, ohne Mehraufwand an Material oder Verwendung teurerer Werkstoffe das dynamische Verhalten oder die Tragf?higkeit von Bauteilen zu verbessern, wird am Beispiel der Grundfrequenz- und Beullaststeigerung von Kreisplatten durch das Einpr?gen von geeigneten Eigenspannungszust?nden dargelegt. Die Ergebnisse einer Optimierung solcher Eigenspannungsfelder werden dargestellt, und die M?glichkeit der Erzeugung geeigneter Eigenspannungszust?nde wird an Hand eines Experiments nachgewiesen.     

Exercise tolerance at 4 and 6 ATA

Seven normal male subjects performed 5-min bicycle exercise ranging from 50-100% maximum oxygen uptake at 4 ATA and three were also studied at 6 ATA. At all pressures, the subjects breathed 0.2 ATA O2 plus nitrogen. All subjects were able to perform maximum work at all pressures. No pressure-dependent variations in heart rate, O2 uptake, or CO2 output were noted. At both 4 and 6 ATA, ventilation was decreased at exercise levels greater than 80% maximum O2 uptake. The magnitude of the decrease was not great, however, and signified only minor CO2 retention. In some instances exercise ventilation closely approached the 15-S maximum breathing capacity and these subjects noted severe dyspnea, possibly due to dynamic compression of large airways. In three subjects, respiratory frequency was measured as well as minute ventilation; this relationship did not change with depth. Subjects performing heavy exercise at 6 ATA noted disturbances of consciousness, presumably due to N2 narcosis.     

Neutralizing Coal Mine Effluent with Limestone to Decrease Metals and Sulphate Concentrations

Abstract.   This paper describes pilot scale tests of a novel process for the neutralisation of acidic mine water. Leachate from a waste coal dump was neutralised with limestone, and iron, aluminium, and sulphate were removed. Specific aspects studied were: the process configuration; the rates of iron oxidation, limestone neutralisation, and gypsum crystallisation; the chemical composition of the effluents before and after treatment; the efficiency of limestone utilisation; and the sludge solids content. The acidity was decreased from 12,000 to 300 mg/L (as CaCO₃), sulphate from 15,000 to 2,600 mg/L, iron from 5,000 to 10 mg/L, aluminium from 100 to 5 mg/L, while the pH increased from 2.2 to 7.0. Reaction times of 2.0 and 4.5 h were required under continuous and batch operations respectively for the removal of 4 g/L Fe (II). The iron oxidation rate was found to be a function of the Fe (II), hydroxide, oxygen, and suspended solids (SS) concentrations. The optimum SS concentration for iron oxidation in a fluidised-bed reactor was 190 g/L. Up-flow velocity had no influence on the rate of iron oxidation in the range 5 to 45 m/h. Sludge with a high solids content of 55% (m/v) was produced. This is high compared to the typical 20% achieved with the high density sludge process using lime. It was determined that neutralisation costs could be reduced significantly with an integrated iron oxidation and limestone neutralisation process because limestone is less expensive than lime, and a high-solids-content sludge is produced. Full scale implementation followed this study.     

Statistical methods for the analysis of tumor multiplicity data

The fit of tumor multiplicity data from 93 mouse skin, lung, and liver carcinogenicity experiments to Poisson, negative binomial, and normal distributions was studied. The data were fitted well by the negative binomial distribution. This distribution has two parameters, the mean tumor multiplicity and an exponent determined by the interanimal homogeneity of tumor response. The value of the latter parameter was related to animal strain and the target tissue studied in the carcinogenicity experiments. The null distribution of the two-sample likelihood ratio test based on the negative binomial with common exponent model for tumor multiplicity data was shown by simulation studies to be approximately chi 2 with 1 d.f. Simulation also indicated that the likelihood ratio test has sufficiently better performance when the negative binomial model is valid to make its use more attractive than the more commonly used Wilcoxon test or Student t test. Charts for estimating the number of animals per group that are required to detect specified differences in tumor multiplicities are provided for several commonly used assays.