Because some of the critical events during the removal of water before the dryer section on a paper machine happen very rapidly within enclosed spaces – such as wet-press nips – there have been persistent challenges in understanding the governing mechanisms. In principle, a fuller understanding of the controlling mechanisms, based on evidence, should permit progress in achieving both higher rates of production of paper and more reliable control of paper attributes. In addition, energy can be saved, reducing environmental impacts. The goal of this article is to review published work dealing both with the concepts involved in water removal and evidence upon which existing and new theories can be based. The scope of this review includes all of the papermaking unit operations between the jet coming from the headbox and the final wet-press nip of an industrial-scale paper machine. Published findings support a hypothesis that dewatering rates can be decreased by densification of surface layers, plugging of drainage channels by fines, sealing effects, flocculation, and rewetting. Ways to overcome such effects are also reviewed.
Water removal by wet pressing on paper machines depends on many factors such as press impulse, pressure, basis weight, equilibrium moisture, rewet, furnish, and fabric properties. These factors must be considered together to estimate wet pressing limits, such as the possibility of attaining 65% solids content on commercial paper machines. We have made such estimates employing the Decreasing Permeability Model (DPM) of wet pressing. This paper describes the utility of this approach and discusses some findings, such as the large dependence of low basis weight grades on equilibrium moisture content, maximum nip pressure, and rewet. The model also estimates the impact of basis weight, web temperature, double-felting, and incoming web solids on water removed.
Refiners develop pulp properties by applying forces on fibres during bar crossings. The size of these forces is critical in developing fibre properties while avoiding fibre shortening. This study has shown that bar force calculated from Specific Edge load (SEL) gives the same result as vector-based derivations of average bar force. Predicted forces agree reasonably well with ones measured by a novel piezo-electric sensor in refiner bars and forces estimated from measurements of fibre shortening.
Antireflection (AR) coatings can improve the viewing experience of a display, including mobile electronic devices such as smartphones, tablets, and laptops that are typically operated on battery power and protected with chemically strengthened glass. In this work, we discuss the trade-offs between optimal user viewing experience in brightly lit environments and battery lifetime for an AR versus a non-AR mobile display. We show that under 400-1,000 lux ambient illumination, an AR-based display can be operated at >30% lower luminance than a non-AR display with similar human perception of contrast based on a perceptual contrast length model, resulting in a potential improvement of >15% in device battery lifetime and a similar proportion of energy savings.
Modern work environments are technologically and socially rich, requiring individuals to manage multiple tasks that involve different technologies and varying degrees of interdependence. Individual and team performance hinge on functional work shifts that can involve changing tasks (multi-tasking), technologies (multi-tooling), and/or teammates (multi-teaming). We extend research on task switching to explain how the social and technological dimensions of tasks affect switch costs. The task switching literature identifies lateral shifts that occur when individuals change tasks. We also consider vertical switches that occur when individuals change from independent (i.e., working alone) to interdependent work (i.e., as part of a team) or from interdependent to independent work. We then integrate personological, social, task, and technological factors into one conceptual framework. Our framework lays the groundwork for understanding the effect of functional work shifts on task and team performance in modern-day work environments.
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