The height variance range for one frequency fringe pattern profilometry

The upper limit on the deepest step of the surface shape that can be accurately determined is an important performance measure associated with the fringe projection profilometry. This metric is evaluated as the variance of height between two adjacent pixels on a fringe patterns reflected from the object surface. This paper presents novel results on this metric based on the Nyquist sampling theorem originally developed in the area of communication theory. Compared to existing results, we indicate that the fringe width and digital image resolution also affect the height variance range significantly. This new result could be used to increase the measurement range for projection system

Manipulating droplet jumping behaviors on hot substrates with surface topography by controlling vapor bubble growth: from vibration to explosion

A major challenge in surface science is rapid removal of sessile liquid droplets from a substrate with complex three-dimensional structures. However, our understanding of interfacial phenomena including droplet wetting dynamics and phase changes on engineered surfaces remains elusive, impeding dexterous designs for agile droplet purging. Here we present a surface topography strategy to modulate droplet jumping behaviors on micropillared substrates at moderate superheat of 20-30 {\deg}C. Specifically, sessile droplets usually dwell in the Wenzel state and therefore the micropillar matrix functions as fin array for heat transfer enhancement. By tuning the feature sizes of micropillars, one can adjust the vapor bubble growth at the droplet base from the heat-transfer-controlled mode to the inertia-controlled mode. As opposed to the relatively slow vibration jumping in seconds, the vapor bubble growth in the inertia-controlled mode on tall-micropillared surface leads to droplet out-of-plane jumping in milliseconds. Such rapid droplet detachment stems from the swift Wenzel-to Cassie transition incurred by vapor bubble burst (explosion), during which the bubble expanding velocity can reach as fast as ~4 m/s. Vapor bubble growth in a droplet and bubble-burst-induced droplet jumping have been less explored. This study unveils the underpinning mechanisms of versatile jumping behaviors of boiling droplets from a hot micro-structured surface and opens up further possibilities for the design of engineered surfaces that mitigate potential damage of vapor explosion or alleviate condensate flooding

Contact line friction analysis of water droplets on micro\nanoscale rough structures

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.In this paper we report the effects of surface roughness on contact line friction coefficients of water droplets on micro- and nano-patterned surfaces. Both advancing and receding contact line friction coefficients have been measured, analyzed and compared on smooth, one-tier (with micropillars), and two-tier (with carbon nanotubes (CNTs) grown on micropillars) surfaces over a wide range of contact line velocities and droplet volumes. Our results indicate that superhydrophobic surfaces with CNTs on top of micropillars can significantly decrease both the advancing and receding contact line friction coefficients. In comparison, both the advancing and receding contact line friction coefficients on smooth surfaces were more than ten times larger than those on superhydrophobic surfaces. However, droplets on one-tier surfaces with only micropillars exhibit different dynamic behaviors on advancing and receding movements. We experimentally investigated the Wenzel-Cassie transition on micropillar structures and found that the receding motion on micropillars is dominated by the Wenzel behavior, which leads to higher receding contact line friction coefficients on one-tier surfaces. However, there is a high tendency for an advancing droplet to exhibit Cassie-type behaviors on one-tier surfaces. As a result, advancing contact line friction coefficient is considerably mitigated on micropillars. On two-tier superhydrophobic surfaces, it was the Cassie–Baxter behavior that dominates both the advancing and receding contact line motions giving rise to less friction coefficients. Furthermore, the effects of surface roughness on contact line hysteresis are discussed in this paper.dc201

Co-ClusterD: A Distributed Framework for Data Co-Clustering with Sequential Updates

Abstract-Co-clustering has emerged to be a powerful data mining tool for two-dimensional co-occurrence and dyadic data. However, co-clustering algorithms often require significant computational resources and have been dismissed as impractical for large data sets. Existing studies have provided strong empirical evidence that expectation-maximization (EM) algorithms (e.g., k-means algorithm) with sequential updates can significantly reduce the computational cost without degrading the resulting solution. Motivated by this observation, we introduce sequential updates for alternate minimization co-clustering (AMCC) algorithms which are variants of EM algorithms, and also show that AMCC algorithms with sequential updates converge. We then propose two approaches to parallelize AMCC algorithms with sequential updates in a distributed environment. Both approaches are proved to maintain the convergence properties of AMCC algorithms. Based on these two approaches, we present a new distributed framework, Co-ClusterD, which supports efficient implementations of AMCC algorithms with sequential updates. We design and implement Co-ClusterD, and show its efficiency through two AMCC algorithms: fast nonnegative matrix tri-factorization (FNMTF) and information theoretic co-clustering (ITCC). We evaluate our framework on both a local cluster of machines and the Amazon EC2 cloud. Empirical results show that AMCC algorithms implemented in Co-ClusterD can achieve a much faster convergence and often obtain better results than their traditional concurrent counterparts

Catalytic oxidation of lignin in solvent systems for production of renewable chemicals: A review

Lignin as the most abundant source of aromatic chemicals in nature has attracted a great deal of attention in both academia and industry. Solvolysis is one of the promising methods to convert lignin to a number of petroleum-based aromatic chemicals. The process involving the depolymerization of the lignin macromolecule and repolymerization of fragments is complicated influenced by heating methods, reaction conditions, presence of a catalyst and solvent systems. Recently, numerous investigations attempted unveiling the inherent mechanism of this process in order to promote the production of valuable aromatics. Oxidative solvolysis of lignin can produce a number of the functionalized monomeric or oligomeric chemicals. A number of research groups should be greatly appreciated with regard to their contributions on the following two concerns: (1) the cracking mechanism of inter-unit linkages during the oxidative solvolysis of lignin; and (2) the development of novel catalysts for oxidative solvolysis of lignin and their performance. Investigations on lignin oxidative solvolysis are extensively overviewed in this work, concerning the above issues and the way-forward for lignin refinery