Developing and fully developed turbulent flow of drag reducing fluids in an annular duct

Velocity profiles for the inner and outer flow regions of annuli are proposed for the turbulent flow of drag reducing fluids. Theoretical expressions for friction factors are developed. From the shear stress equations and the velocity profiles, estimates for the entrance lengths are given.     

Empirical equations for the perforation of mild steel plates

The experimental results for the perforation energy of mild steel plate struck by flat-ended, non-deforming, cylindrical penetrators have been correlated using the principles of dimensional analysis. A correlation is presented for long penetrators. It is shown that for short penetrators a different response of the target is observed and that, at present, there are insufficient published data to produce a unifying correlation.     

Lateral habits ofn-alkane single crystals

The lateral crystal habits ofn-alkanes (n-C _n H_2n+2) have been observed just below the melting points by optical microscopy forn=18, 19, 20, 22, 24, 34, 44, 50 and 65. The shape of the crystals depends on the crystal phase: circular in the rotator phase, lenticular in phase C, and diamond in the low-temperature phase. The rounding of the lateral shape can be explained in terms of thermal roughening of the lateral faces in the disordered phases at high temperature.     

Elastic effects in the flow of polymer solutions in channels of variable cross section and a porous medium

The manifestation of elastic effects during the filtration of polymer solutions is analyzed theoretically.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 390–397, September, 1985.     

一方水土养一方人

我国幅员辽阔，产物众多，各地的饮食习惯也不同。非常有趣的是，特别的饮食习惯不仅影响了各地人的生活，甚至还塑造了他们的性格。正所谓“一方水土养一方人”。     

Perceived risk and trust associated with purchasing at electronic marketplaces

Understanding consumer behaviour is of vital importance to consumer-oriented e-business models today. In this paper, we study the relationships between consumer perceptions of risk and trust and the attitude towards purchasing at a consumer-to-consumer electronic marketplace (EM). Typical for EM settings is that consumer behaviour is subject to perceptions of the selling party as well as of the institutional structures of the intermediary that is operating the EM. Building upon the well-established literature of trust, we consider the concepts of intermediary trust and seller trust. We extend this categorisation by introducing the concepts of intermediary risk and seller risk. We developed measurement instruments for intermediary risk and seller risk. All measurement scales have acceptable alphas and are unidimensional. An empirical study is conducted to explore the relationships between the risk and trust types and consumer purchase attitude. The results reveal significant, direct effects of seller trust and seller risk. Second-order effects of intermediary trust and intermediary risk are investigated and reported. The paper concludes with general observations and recommendations for research and practice.     

Effect of starting particle size on hot-pressing of magnesium oxide powder prepared by vapour-phase oxidation process

Effect of starting particle size on hot-pressing of magnesium oxide (MgO) powder was examined using seven kinds of MgO powders prepared by a vapour-phase oxidation process; the average primary particle sizes were 11, 25, 32, 44, 57, 107 and 261 nm. These compressed powders (compacts) were hot-pressed at a temperature between 900 and 1300°C. The densifications of these compacts during the hot-pressing proceeded via (i) the sintering of primary particles within secondary particles and the rearrangement of secondary particles/grains (900°C), (ii) the gradual grain growth controlled by the pore migration (900∼1100°C) and (iii) the rapid grain growth due to the active mass transfer (1300°C); the grain sizes of MgO compacts hot-pressed at and below 1100°C were <1 μm, while those at 1300°C attained 20∼30 μm. The transluscent compact with the relative density of 99.7% could be obtained when the compressed powder with the average primary particle size of 44 nm was hot-pressed at a temperature as low as 1100°C for 1 h. This revised version was published online in November 2006 with corrections to the Cover Date.