A MODEL OF THE TURBULENT BURST PHENOMENON: TRANSITIONAL TURBULENT FULLY DEVELOPED FLOW IN CIRCULAR TUBES

The surface renewal approach is used in this paper to analyze transitional turbulent, fully developed flow in circular tubes. The analysis involves a minimum level of empiricism and gives rise to calculations for mean velocity distribution and friction factor that are consistent with experimental data for laminar, transitional turbulent, and fully turbulent conditions.     

多场耦合作用下流变液悬浮性态仿真与分析

仿真分析了磁场和剪切场作用下双分散、单分散磁流变液的微观结构演化,从4个方面考察了磁流变液悬浮性态：微观结构相变,链长分布,聚合结构各向异性和悬浮粒子运动涨落。结果表明,在磁场作用下,场强幅值越高,相态迁移的时间越短、簇-墙相越明显;在低磁场时,双分散悬浮较单分散悬浮容易形成长链,而在中、高磁场时,单分散悬浮却较双分散悬浮容易形成长链;磁极粒子具有智能特性,在无剪切场作用下总是寻找最易形成墙的方向排列成簇,而在稳态剪切作用下沿流场方向形成通长墙相以抑制流场的输运;外加磁场有助于减小悬浮粒子的运动涨落,但在剪切场的引导作用下,磁场强度的变化对悬浮粒子运动涨落无明显影响。     

Remote,surface and laboratory detection of radioactive minerals of Rosetta black-sand beach deposits,Egypt

Abstract

Detailed aerial and ground radiometric surveys were conducted on the coastal plain of the Mediterranean Sea, on both sides of the estuary of the Rosetta branch of the River Nile. Auger samples representing the upper 1 m, were collected and analysed for the two principal radioactive minerals in the black sands, zircon and monazite.

The results obtained by the various methods, particularly aeroradiometry, revealed five main zones of heavy mineral concentration along the beach to the east and west of the Rosetta estuary. The present-day Rosetta branch is responsible for the formation of the first zone of mineral concentration. The second and fifth zones can be related to the ancient extinct estuaries of the Bolbitine and Sebennytic branches mentioned by Ball (1942) (after Herodotus, 450 B.C.). The third and fourth zones are believed to correspond to two ancient extinct estuaries of the River Nile, which were probably not in existence at the time of Herodotus and therefore were not reported by Ball (1942).

The study revealed that there is a general direct correlation between the aerial data and that from ground radiometry and zircon and monazite tenors as in the case of Damietta black-sand beach deposits (Meleik et al. 1978).

It was found that the mean background radioactivity either from the air or from the ground, as well as the correlation coefficients, are generally higher and stronger on the western side of the Rosetta estuary than on its eastern side. Moreover, the mean concentration of zircon on the western side (0·62 per cent) reaches approximately 1·5 times that on the eastern side (0·39 per cent), while that of monazite remains almost the same westwards (0·16 per cent) and eastwards (0·14 percent).     

THE EFFECT OF PHYTATE AND FIBER CONTENT ON COOKING QUALITY IN FABA BEANS

Seventy-six faba bean lines were analyzed for their phytic acid content in the whole seeds and in the cotyledons. The fiber content was also determined in 17 Faba bean lines. The seed weights; % testa weight-of the seeds; and % moisture uptake (water imbibition) after overnight soaking in distilled water or increasing concentrations of EDTA solutions were measured and recorded. The relation between the above mentioned dependent variables and the cooking time for seed softening (min.) in 76 faba bean lines was studied and simple and multiple correlation coefficients were computed with a total of 70 operations. Significant correlation coefficients were found between phytic acid content in the cotyledons, % testae weight of the seeds; moisture uptake after soaking the seeds in distilled water overnight and cooking time for 50% softening (min). The faba bean lines 606/ 303; 606/ 308, 608/ 334, 609/ 350, proved to be of excellent cooking quality, since their cooking time for 50% seed softening did not exceed 10 min.