Electrostatic charging of jumping droplets

With the broad interest in and development of superhydrophobic surfaces for self-cleaning, condensation heat transfer enhancement and anti-icing applications, more detailed insights on droplet interactions on these surfaces have emerged. Specifically, when two droplets coalesce, they can spontaneously jump away from a superhydrophobic surface due to the release of excess surface energy. Here we show that jumping droplets gain a net positive charge that causes them to repel each other mid-flight. We used electric fields to quantify the charge on the droplets and identified the mechanism for the charge accumulation, which is associated with the formation of the electric double layer at the droplet–surface interface. The observation of droplet charge accumulation provides insight into jumping droplet physics as well as processes involving charged liquid droplets. Furthermore, this work is a starting point for more advanced approaches for enhancing jumping droplet surface performance by using external electric fields to control droplet jumping.United States. Dept. of Energy. Office of Basic Energy Sciences (Solid-State Solar-Thermal Energy Conversion Center Award DE-FG02-09ER46577)United States. Office of Naval ResearchNational Science Foundation (U.S.) (Major Research Instrumentation Grant for Rapid Response Research (MRI- RAPID))National Science Foundation (U.S.) (Award ECS-0335765)National Science Foundation (U.S.). Graduate Research Fellowship Program (Grant 1122374

Practices and Performance in Constraints Management Production Planning and Control Systems

This chapter provides !rst a literature review of the characteristics of production systems operating according to the principles of Theory of Constraints (TOC). The analysis is conducted by a comparison of these characteristics with those of three well-known production systems, namely Dispatching, Kanban and Daily Rate. The literature review highlights that the most signi!cant differences are pertinent to the third level of the manufacturing planning and control system, the so-called production executive control or shop floor control sub-system. An interpretative framework for discussing the distinguishing characteristics of TOC in production management is !nally proposed. The second part of the chapter is dedicated to study the relationship between TOC production and operational performance of manufacturing plants. The study is based on data collected from 61 manufacturing plants located in Europe through an extensive questionnaire survey. Analysis of variance technique and regression models have been employed to test the research hypotheses. The results detect many differences and similarities in adoption of TOC practices across the plants and suggest that manufacturing managers should consider adopting some TOC practices instead of others. In particular the drum\u2013buffer\u2013rope methodology, the development of a Master Production Schedule based on constraints and the use of Non-constraint resources with excess capacity are among the most important practices to enhance competitive performance of manufacturing plants