CMOS high-speed dual-modulus frequency divider for RF frequencysynthesis

The architecture of a high-speed low-power-consumption CMOS dual-modulus frequency divider is presented. Compared to other designs fabricated with comparable CMOS technologies, this architecture has a better potential for high-speed operation. The circuit consumes less power than previously reported CMOS circuits, and it approaches the performance previously achieved only by bipolar or GaAs devices. The proposed circuit uses level-triggered differential logic to create an input-frequency-entrained oscillator performing a dual-modulus frequency division. In addition to high-speed and low-power consumption, the divider has a low-input signal level requirement which facilitates its incorporation into RF applications. Fabricated with a 1.2-μm 5-V CMOS technology, the divider operates up to 1.5 GHz, consuming 13.15 mW, and requiring less than 100 mV rms input amplitude     

Evaluating the Effect of Downstream Channel Width Variation on Hydraulic Performance of Arched Plan Stepped Spillways

In the present study, a 3D physical model with a scale of 1:50 was developed based on the Germi-Chay dam. The model was used to assess the impact of downstream channel width variation on the efficiency of arched plan stepped spillways. Four ratios of downstream channel width to spillway crest width (Wch/W) were considered which range from 0.214 to 0.286. The hydraulic parameters such as water surface profile, static pressure, discharge coefficient, energy dissipation, and stage-discharge were assessed for each model. Results of the experiments indicated that the values of the discharge coefficient increased with increasing the upstream head values before the submergence state occurrence. However, in this state, the downstream channel width variations had no significant impact on the discharge coefficient. On the other hand, with spillway submergence, influence on discharge coefficient was observed when width variations occurred. Observations showed that an increase in the width ratio caused a decrease in static pressure. In addition, the results of the submerged state clearly showed the effect of the width ratio variations on energy dissipation. For a particular discharge, the highest width ratio led to minimal energy dissipation. Results revealed that the most efficient model was when Wch/W?=?0.286. This model was the only one that successfully passed the probable maximum flood discharge in the maximum allowable height (5 m).

     

How do entrepreneurs learn and engage in an online community-of-practice? A case study approach

This paper investigates the ways in which entrepreneurs use communities of practice (CoPs) to express themselves, using narrative theory and rhetorical analysis, to gain insight into an electronic social network medium, namely, YoungEntrepreneur.com. In particular, the study focuses on CoPs themes, including why entrepreneurs engage in CoPs, what role the moderators and resident entrepreneurs can play in managing online CoPs, on communication rituals of the knowledge sharing through interactivity, and on ‘how to develop an intervention’ to maintain and stimulate entrepreneurs for engaging in an online community. Findings reveal that the topic title plays a major role in attracting people. Successful topics with successful conclusions (in terms of the original query that was answered) will not necessarily get high responses and vice versa. It is observed that the domain expert does not play a big role in keeping the discussion going. Finally, the study also discovered that entrepreneurs like to communicate in a story telling genre. A comprehensive set of engagement measurement tools are introduced to effectively measure the engagement in a virtual CoP, along with a classification to define and categorise discourse of messages in terms of content and context, which allow practitioners to understand the effectiveness of a social networking site.