Correlation of strength of 75 mm diameter and 100 mm diameter cylinders for high strength concrete

Results of statistical analysis of test data are presented to establish if there is a correlation between the strength of 75- and 100-mm-diameter cylinders for concrete with strength between 110 and 160 MPa. A linear regression analysis showed that strength measured on 75-mm cylinders is within 5% of the corresponding strength measured on 100-mm cylinders. A more detailed analysis of the difference between the mean strengths of the two sizes of cylinder of each group of the tests indicated that 75- and 100-mm cylinders measure the concrete strength within 4%. It is concluded that 75-mm cylinders are suitable for compressive strength testing of high strength concrete (>100 MPa). For strength of concrete greater than 150 MPa, 75-mm cylinders are likely to measure smaller concrete strength than the corresponding 100-mm cylinders.     

Potential for detoxified castor meal

Castor oil is a useful chemical raw material, but the pomace remaining after its extraction is potentially toxic and allergenic. Improving the economic value of castor pomace will provide considerable incentive for increased production of castor seed in the United States. Processes for detoxifying and deallergenating castor meal have been developed along with means for evaluating these processes. Castor meal may be used as a feed supplement for both ruminant and nonruminant animals. One of 21 papers presented at the Symposium, “Oilseed Processors Challenged by World Protein Need,” ISF-AOCS World Congress, Chicago, September 1970. W. Utiliz. Res. Dev. Div., ARS, USDA.     

Studies on the effect of cobalt addition to the nickel hydroxide electrode

Ni(OH)₂ electrodes are known to take up potassium and lithium ions from electrolytes on cycling. The present study revealed lower levels of adsorption of potassium and lithium in the case of cobalt co-deposited -nickel hydroxide electrodes although similar uptake patterns were clearly visible. At room temperatures, addition of cobalt has also been found to be advantageous in so far as the electrode performance on repeated cycling in 1 M LiOH+4 M KOH is concerned. In pure KOH, however, cobalt addition has been found to have a detrimental effect on the life of the electrode although an easier charging process is observed in the initial stages. Increase in the end-of-charge potential in lithiated electrolyte was found to be a direct consequence of lithium adsorption by the cobalt co-deposited -nickel hydroxide electrodes.     

On the deterioration of ß″-alumina ceramics under electrolytic conditions

The degradation ofβ′'-alumina under electrolytic conditions was investigated at room temperature. With the use of an electrical-mechanical analogue, it was demonstrated that a large current concentration exists at the peripheries of blocked or unwetted areas. Thus, actual current densities at the sites of failure can be several times larger than the average current density. Implications regarding wetting ofβ′'-alumina by sodium are discussed. The concept of current focusing at the tips of sodium-filled cracks is demonstrated in a room temperature test.     

Hydroxylation of secondary bile acids in the perfused prairie dog liver

Taurolithocholic acid and deoxycholic acid were perfused into isolated prairie dog livers. Taurolithocholic acid was 7α-hydroxylated to form taurochenodeoxycholic acid, whereas deoxycholic acid was conjugated and 7α-hydroxylated to form taurocholic acid. The low concentrations of secondary bile acids observed in prairie dog bile are due, at least in part, to active bile acid 7α-hydroxylase(s) in the liver of these animals.     

Optimal temperature profiles for nylon 6 polymerization in plug-flow reactors

Optimal temperature profiles for nylon 6 polymerization in plug-flow reactors have been obtained under different conditions using a reasonable objective function which gives more flexibility to a designer than those studied earlier. Computations suggest that the temperatures at the feed end of the reactor must be maintained at the highest permissible level (determined by the boiling point of the ?-caprolactam) so as to force the degree of polymerization rapidly to the desired value. Thereafter, the temperatures should be reduced in order to minimize the undesirable cyclic dimer concentration, and, finally, near the exit of the reactor, the temperature must once again be increased in order to attain higher monomer conversion. The effect of a systematic change of values of the various design variables, one by one, is studied. The profile obtained differs substantially from those obtained by earlier workers because of the difference in the objective function as well as in the kinetic mechanism associated with the formation of the cyclic oligomer. Attempts are also made to obtain a global optimal scheme to produce a polymer of a desired degree of polymerization.     

Frontier production functions: Improved procedures for estimation and application

This paper develops improved estimating techniques for frontier production functions and measures of technical efficiency. A clustering analysis procedure is introduced to isolate subsets of data observations on the basis of qualitative considerations. A dominance test is formulated to screen out data observations which will not influence the frontier production function. A computational algorithm is presented to efficiently implement these procedures. These techniques are applied to the steam-electric generating industry and discussed.     

A test of randomness based on the minimal spanning tree

We present a test of randomness based on the edge length distribution of the Minimal Spanning Tree.     

Simulated strength-grain size study using a glass-glass-ceramic composite system

Strength studies have been conducted on composite specimens of a glass and a glass-ceramic. The composite system consists of a glass fillet on the surface of a bar-shaped glass-ceramic. Controlled surface flaws have been introduced into the glass fillet via indentation. Strength has been studied as a function of indent load and the size of the glass fillet. The glass-glass-ceramic composite system is meant to represent a polycrystalline ceramic with duplex microstructure such that the glass fillet simulates a large single crystal. The glass-ceramic on the other hand simulates a fine-grained matrix. Thus, the present study simulates a strength versus grain size relation for a polycrystalline ceramic. The data indicate that in several coarse grained ceramics, an inherent crack arrests within the body after initial propagation prior to catastrophic failure. Microscopic examination coupled with an electric potential method indicated that the initial crack arrests at the glass-glass-ceramic interface. The data also suggests that differences in elastic constants across an interface may have a significant influence on strength.