A genetic algorithm for the minimum weight triangulation

In this paper, a new method for the minimum weight triangulation of points on a plane, called genetic minimum weight triangulation (GMWT), is presented based on the rationale of genetic algorithms. Polygon crossover and its algorithm for triangulations are proposed. New adaptive genetic operators, or adaptive crossover and mutation operators, are introduced. It is shown that the new method for the minimum weight triangulation can obtain more optimal results of triangulations than the greedy algorithm.published_or_final_versio

Proteomic analyses reveal distinct chromatin-associated and soluble transcription factor complexes.

The current knowledge on how transcription factors (TFs), the ultimate targets and executors of cellular signalling pathways, are regulated by protein-protein interactions remains limited. Here, we performed proteomics analyses of soluble and chromatin-associated complexes of 56 TFs, including the targets of many signalling pathways involved in development and cancer, and 37 members of the Forkhead box (FOX) TF family. Using tandem affinity purification followed by mass spectrometry (TAP/MS), we performed 214 purifications and identified 2,156 high-confident protein-protein interactions. We found that most TFs form very distinct protein complexes on and off chromatin. Using this data set, we categorized the transcription-related or unrelated regulators for general or specific TFs. Our study offers a valuable resource of protein-protein interaction networks for a large number of TFs and underscores the general principle that TFs form distinct location-specific protein complexes that are associated with the different regulation and diverse functions of these TFs

A unified lattice Boltzmann model and application to multiphase flows

In this work, we develop a unified lattice Boltzmann model (ULBM) framework that can seamlessly integrate the widely used lattice Boltzmann collision operators, including the Bhatnagar–Gross–Krook or single-relation-time, multiple-relaxation-time, central-moment or cascaded lattice Boltzmann method and multiple entropic operators (KBC). Such a framework clarifies the relations among the existing collision operators and greatly facilitates model comparison and development as well as coding. Importantly, any LB model or treatment constructed for a specific collision operator could be easily adopted by other operators. We demonstrate the flexibility and power of the ULBM framework through three multiphase flow problems: the rheology of an emulsion, splashing of a droplet on a liquid film and dynamics of pool boiling. Further exploration of ULBM for a wide variety of phenomena would be both realistic and beneficial, making the LBM more accessible to non-specialists. This article is part of the theme issue ‘Progress in mesoscale methods for fluid dynamics simulation’

Droplet impacting a superhydrophobic mesh array: Effect of liquid properties

Generation of monodisperse droplets by a large droplet impacting a mesh array is a common technique in microfluidic engineering, materials science, and drug production. Understanding the dynamic mechanism behind this is critical to controlling this process. This work uses a nonorthogonal multiple-relaxation-time lattice Boltzmann (LB) method to simulate a droplet impacting a mesh array. By varying the droplet viscosity and surface tension, a comprehensive parametric study is carried out to investigate the influence of droplet properties on the dynamic process of droplet impact, penetration, and fragmentation. The results indicate that the inertial effect dominates the spread stage of droplet impact. At later stages, the viscous drag and surface tension act to prevent the spread of the droplet, which results in different maximum spreading diameters. The penetration of the droplet through the mesh initially leads to the formation of a liquid jet, the length of which is determined by the competition between the dynamic pressure and capillary pressure. Different jet breakup lengths are observed for various Weber numbers. The maximum spreading diameter and jet breakup length are predicted by an extended model over a wide range of liquid properties, in good agreement with the LB simulation results. An analysis is also conducted from an energy perspective. It is found that the surface energy significantly decreases after the fragmentation of the high-viscosity droplet, which is caused by the merge of satellite droplets after the jet breakup

Modeling of biomass pyrolysis in a bubbling fluidized bed reactor: Impact of intra-particle heat conduction

Biomass fast pyrolysis in a fluidized bed reactor is studied numerically by a three-fluid model where the biomass thermal decomposition is introduced with multi-step kinetics. Different superficial velocities of fluidizing gas are defined to investigate the hydrodynamics of the fluidized beds and the consequent influence on the yield fractional distribution of end-products. Heat conduction inside particles is considered indirectly through modifying the rate constants of biomass reaction scheme. The simulation results show that superficial velocity has to be designed carefully based on balancing the char-removal efficiency and biomass heating up rate; compared to the experimental data, the modified reaction scheme can be employed to describe the intra-particle heat penetration, qualitatively, but the accuracy of predicting the end-product yields needs to be improved

An intelligent control of NH3 injection for optimizing the NOx/NH3 ratio in SCR system

The distribution of nitrogen oxides (NOx) flux within the cross-section area in front of ammonia injection grid (AIG) under different operating conditions was obtained by computational fluid dynamics (CFD) method. Weight of NOx flux in the sub-zone corresponding to each of the ammonia (NH3) injection branch-pipes of AIG system was analyzed and the sensitivity of which against the plant power load was figured out. A number of “critical” ammonia injection branch-pipes were determined with regard to the weight sensitivity analysis. The selected “critical” branch-pipes were changed to be controlled by the automatic valves, and an intelligent tuning strategy was proposed. The NOx/NH3 mixing stoichiometry over the cross-section area in front of AIG system was significantly modified for the high utilization ratio of ammonia. A case work was launched on the selective catalytic reduction (SCR) system of a 660 MW plant. As a result, the ammonia consumption rate (ACR) was found to be reduced by 6.44% compared to that under previous control system, and was 9.31% lower than that of the unapplied system. The methodology for determining the “critical” branch-pipes and intelligent tuning strategy of ammonia injection notably saved the ammonia consumption of SCR system, and the formation of ammonium bisulfate (ABS) were greatly confined

Lattice Boltzmann simulation of a water droplet penetrating a micropillar array in a microchannel

Water droplets penetrating a microchannel equipped with an array of micropillars are commonly seen in engineering applications, ranging from micro-electro-mechanical systems to macro-heat-transfer facilities. Understanding the detailed droplet dynamics in this process is therefore beneficial to the advancement of many fields of industry. In this study, we adopt a nonorthogonal multiple-relaxation-time lattice Boltzmann model to simulate a water droplet penetrating a micropillar array in a microchannel. We first validate our model against the experimental results of (a) off-center impact of a water droplet on a ridged superhydrophobic surface and (b) impact of a water droplet on a curved superhydrophobic surface. Then a comprehensive parametric study is carried out by changing the droplet initial velocity, opening fraction of the micropillar array, and wettability of the micropillar surface. It is found that when the droplet penetrates the micropillar array, its fingering dynamics in the longitudinal direction is governed by the competition between the dynamic and capillary pressures, while the permeation process in the lateral and vertical directions is dominated by the capillary effect. The change of the droplet initial velocity and configuration setup can significantly influence the droplet penetration velocity, maximum wetted surface area, and penetration rate. Finally, a theoretical model is proposed to describe the transient evolution of the droplet penetration mass for a variety of Weber numbers, opening fractions, and static contact angles

Green Synthesis of Tunable Fluorescent Carbon Quantum Dots from Lignin and Their Application in Anti-Counterfeit Printing

Lignin converted to carbon quantum dots (CQDs) attracts tremendous attention for large-scale production of carbon nanomaterials and value-added disposal of biomass wastes (such as the black liquor from pulping industry and the residue from hydrolysis of biomass). The green synthesis of lignin-derived CQDs is reported via a facile two-step method with the adjustment of acid additives containing N or S. The resulting series of CQDs exhibit bright fluorescence in gradient colors from blue to yellowish green, among which the N, S co-doped CQDs with the addition of 2,4-diaminobenzene sulfonic acid show an optimal fluorescence quantum yield (QY) of 30.5%. The red-shift photoluminescence emission behaviors of these CQDs can be attributed to the increased graphitization degree and reduced optical energy band gaps (2.47 → 2.17 eV) with regard to the incorporation of various heteroatoms. The improved fluorescence QYs are consistent with the variation trend of the increased N/C content in the CQDs. The yellowish green-emissive CQDs with bright fluorescence, strong water solubility, and excellent chemical stability perform well in anti-counterfeiting printing. The promising and sustainable approach for the synthesis of tunable fluorescent CQDs exhibits the value-added utilization of lignin for the fluorescence ink production

Molecular dynamics study on evaporation of metal nitrate-containing nanodroplets in flame spray pyrolysis

Flame spray pyrolysis (FSP) provides an advantageous synthetic route for LiNi1−x−yCoxMnyO2 (NCM) materials, which are one of the most practical and promising cathode materials for Li-ion batteries. However, a detailed understanding of the NCM nanoparticle formation mechanisms through FSP is lacking. To shed light on the evaporation of NCM precursor droplets in FSP, in this work, we employ classical molecular dynamics (MD) simulations to explore the dynamic evaporation process of nanodroplets composed of metal nitrates (including LiNO3, Ni(NO3)2, Co(NO3)2, and Mn(NO3)2 as solutes) and water (as solvent) from a microscopic point of view. Quantitative analysis on the evaporation process has been performed by tracking the temporal evolution of key features including the radial distribution of mass density, the radial distribution of number density of metal ions, droplet diameter, and coordination number (CN) of metal ions with oxygen atoms. Our MD simulation results show that during the evaporation of an MNO3-containing (M = Li, Ni, Co, or Mn) nanodroplet, Ni2+, Co2+, and Mn2+ will precipitate on the droplet surface, forming a solvent–core–solute–shell structure; whereas the distribution of Li+ within the evaporating LiNO3-containing droplet is more even due to the high diffusivity of Li+ compared with other metal ions. For the evaporation of a Ni(NO3)2- or Co(NO3)2-containing nanodroplet, the temporal evolution of the CN of M–OW (M = Ni or Co; OW represents O atoms from water) suggests a “free H2O” evaporation stage, during which both CN of M–OW and CN of M–ON are unchanged with time. Evaporation rate constants at various conditions are extracted by making analogy to the classical D2 law for droplet evaporation. Unlike Ni or Co, CN of Mn–OW keeps changing with time, yet the temporal evolution of the squared droplet diameter indicates the evaporation rate for a Ni(NO3)2-, Co(NO3)2-, or Mn(NO3)2-containing droplet is hardly affected by the different types of the metal ions