Clay-Particle Dispersion by Ultrasons

The dispersion of 1.0% kaolin suspensions in water was studied utilizing ultrasonic vibrational energy. The effect of time of exposure to ultra-sons was examined microscopically and turbidi-metrically by means of a spectrophotometer. Complete deagglomeration and dispersion were accomplished in 10 minutes of exposure to ultra-sons without any apparent deleterious effects on the primary particle size of the kaolin. The effects of two accepted methods of dispersion were compared with the ultrasonic method.     

Low-Temperature Sintering of Aluminum Oxide

A fine-sized (∼0.1 μm), agglomerate-free Al₂O₃ dispersion was used to prepare homogeneous green bodies with ∼69% relative density and ∼10-nm median pore radius. Samples could be sintered at 1150°C to a relative density >99.5% and an average grain size of 0.25 μm.     

The impact of status and audio conferencing technology on business meetings

This field study examining the effects of organizational status and multimedia audio communications technology on communication patterns in business meetings confirms that high status group members verbally dominate discussions and have more control over the flow of the proceedings. However, it reveals a new and surprising finding: multimedia communications technology can in fact exaggerate status constraints in contrast to findings that there is no effect or an equalizing effect on status inequalities of text-based conferencing technology. It appears that in audio conferences, the lack of non-verbal cues that can aid turn-taking combined with (1) the participants' knowledge of the group's status hierarchy and (2) the tendency to compare oneself unfavourably to those of higher status, makes it more difficult for lower status individuals to contribute verbally to discussions than in face-to-face interactions. Such status constraints may have both positive and negative impacts on group communication effectiveness, these and implications for the design and implementation of multimedia communications technology are discussed.     

Microstructure and Magnetic Properties of Lead Ferrite

Unoriented lead ferrite specimens were prepared by calcining and sintering techniques. Specimens having an initial composition of Pb0.5Fe₂O₃ had the best permanent magnet properties (for nondoped material). The effects of small amounts of added oxides on the microstructure and magnetic properties were also determined. Silica and boria were most effective in raising the (B_aH^a)_max to over 1.4 × 10⁶ G.Oe as compared to 0.9 to 1.1 × 10⁵ G.Oe for commercial un oriented barium ferrite magnets. Optical and electron microscopy revealed that silica and boria form low melting phases as the specimens are sintered, which, acting as fluxes (probably by a solution-precipitation mechanism), enhance the densification of the magnets, thereby raising the B_r, and (B_aH_a)_max, values. On cooling, these nonmagnetic low-melting phases are retained at the ferrite grain boundaries where they inhibit domain wall motion which would otherwise lead to a reduction in coercive force. Although these magnets are termed "un oriented" to distinguish them from "oriented" ferrites which are purposely aligned before sintering, a slight orientation is imparted to the polycrystalline compact during the pressing operation before sintering. The silica and boria additions increase the degree of orientation by accelerating the rate of densification. The increase in orientation accounts for part of the increase in B_r, and (B_a, H_a)_max.     

WEAKENING STRONG BLACK POLITICAL EMPOWERMENT: IMPLICATIONS FROM ATLANTA'S 2009 MAYORAL ELECTION

Atlanta is perhaps the city with the greatest degree of black political empowerment (BPE) in the United States. Yet in 2009 a relatively weak white mayoral candidate nearly won the general and runoff elections over a field of stronger black candidates. Why? Treating Atlanta as a prototypical case, the article examines factors that undermine the capacity of blacks to retain control of mayoralties in strong BPE cities, with an emphasis on disruptions to black electorates, discontent among black citizens, and reinvestment in electoral politics by whites at the local level.     

Research on system zeros: a survey

This report provides a review of notable publications regarding the topic of zeros of multivariable systems in the period from 1970 into 1989. Particular attention is paid to relationships between definitions of such zeros and their theoretical development. Transmission, invariant, system, module, infinite and finite zeros are addressed, the latter subdivided into a hierarchical structure with respect to information considered in the definition process.     

三角铣头强化了5轴加工中心的通用性

大、重型零件,例如透平轮毂、风力发电机或重型机械的齿轮,泵体、工业及船用发动机缸体、冲压成型模具的模板等等,主要是单件或小批量生产.这类零件大部分是由分包制造商和维修公司制造的.因此,这类工件不能使用专用夹具装夹.而且,在大型车床或加工中心上加工此类工件时,找正工作非常耗时耗力.     

THE RESPONSE OF UNSYMMETRIC LAMINATES TO SIMPLE APPLIED FORCES

SUMMARY

The snap-through behaviour from one cylindrical configuration to another of an unsymmetric (O₂/90₂)T cross-ply laminate is modelled using a simple Rayleigh-Ritz approach. Snap-through is caused by two opposing moments which are produced by opposing forces acting through known moment arms. The snap-through force is predicted, and the predictions are compared with experimental measurements. Correlation is good. The experimental set-up used to measure the force is described, as are the details of the Rayleigh-Ritz approach.