Lagrangian particle tracking with new weighted fraction Monte Carlo method for studying the soot particle size distributions in premixed flames

Purpose The purpose of this paper is to study the soot formation and evolution by using this newly developed Lagrangian particle tracking with weighted fraction Monte Carlo (LPT-WFMC) method. Design/methodology/approach The weighted soot particles are used in this MC framework and is tracked using Lagrangian approach. A detailed soot model based on the LPT-WFMC method is used to study the soot formation and evolution in ethylene laminar premixed flames. Findings The LPT-WFMC method is validated by both experimental and numerical results of the direct simulation Monte Carlo (DSMC) and Multi-Monte Carlo (MMC) methods. Compared with DSMC and MMC methods, the stochastic error analysis shows this new LPT-WFMC method could further extend the particle size distributions (PSDs) and improve the accuracy for predicting soot PSDs at larger particle size regime. Originality/value Compared with conventional weighted particle schemes, the weight distributions in LPT-WFMC method are adjustable by adopting different fraction functions. As a result, the number of numerical soot particles in each size interval could be also adjustable. The stochastic error of PSDs in larger particle size regime can also be minimized by increasing the number of numerical soot particles at larger size interval.

Size-Based Routing Policies: Non-Asymptotic Analysis and Design of Decentralized Systems

Size-based routing policies are known to perform well when the variance of the distribution of the job size is very high. We consider two size-based policies in this paper: Task Assignment with Guessing Size (TAGS) and Size Interval Task Assignment (SITA). The latter assumes that the size of jobs is known, whereas the former does not. Recently, it has been shown by our previous work that when the ratio of the largest to shortest job tends to infinity and the system load is fixed and low, the average waiting time of SITA is, at most, two times less than that of TAGS. In this article, we first analyze the ratio between the mean waiting time of TAGS and the mean waiting time of SITA in a non-asymptotic regime, and we show that for two servers, and when the job size distribution is Bounded Pareto with parameter α=1, this ratio is unbounded from above. We then consider a system with an arbitrary number of servers and we compare the mean waiting time of TAGS with that of Size Interval Task Assignment with Equal load (SITA-E), which is a SITA policy where the load of all the servers are equal. We show that in the light traffic regime, the performance ratio under consideration is unbounded from above when (i) the job size distribution is Bounded Pareto with parameter α=1 and an arbitrary number of servers as well as (ii) for Bounded Pareto distributed job sizes with α∈(0,2)\{1} and the number of servers tends to infinity. Finally, we use the result of our previous work to show how to design decentralized systems with quality of service constraints.

Rain Drop Size Distribution Analysis at a Tropical Location Near Land-sea Boundary

Rain events can be characterized by rain drop size distribution (DSD) that denotes the number of drops as a function of diameter per unit size interval and per unit volume of space. DSD describes the microstructure of precipitation during different phases of rain varying both spatially and temporally. DSD can be influenced by the nature and origin of rain. The present study investigates the role of continental and maritime airflow in influencing the precipitation features near the land-sea boundary. Rain DSD data used in the present analysis are collected from a ground based disdrometer located at Kolkata, India during the year of 2011-2017. The dataset is divided into two categories namely, maritime and continental rainfall, based on the airflow trajectories associated with rainfall, respectively, from Bay of Bengal and from land surface in the west of Kolkata, as derived from TRAJSTAT software. Variations of the DSD parameters using Gamma model is presented showing the abundance of smaller drops during maritime rain events whereas dominance of larger raindrops in the case of the continental rain events. The Z-R relations are also found to be significantly different for these two types of rain. The present study reveals the microstructures of rain at a location where the influences of both land and sea climatic features prevail.

When ANOVA Isn't Ideal: Analyzing Ordinal Data from Practical Work in Biology

Data collected in many biology laboratory classes are on ratio or interval scales where the size interval between adjacent units on the scale is constant, which is a critical requirement for analysis with parametric statistics such as t-tests or analysis of variance. In other cases, such as ratings of disease or behavior, data are collected on ordinal scales in which observations are placed in a sequence but the intervals between adjacent observations are not necessarily equal. These data can only be interpreted in terms of their order, not in terms of the differences between adjacent points. They are unsuitable for parametric statistical analyses and require a rank-based approach using nonparametric statistics. We describe an application of one such approach, the Kruskal-Wallis test, to biological data using online freeware suitable for classroom settings.

Plastic waste input from Guadalquivir River to the ocean

<p>Around 8 million tons of plastic waste are leaked from land into the ocean annually. One of the main pathways of plastic input into the ocean is rivers, but there is no comprehensive information about the amount and nature of litter transported. This study presents results of a monthly monitoring over a two years period in the estuary of Guadalquivir River, southern Spain. The samples, which consisted of passive hauls, were taken from a traditional glass eel fishing boat anchored with three nets working in parallel. The nets, with a mesh of 1 mm and an opening of 2.5 (width) × 3 (depth) metres, filtered around 60,000 m<sup>3</sup> per sample. Our methodological approach allowed characterization of virtually all plastic sizes in river waters, comprising micro-, meso- and macroplastics. Plastic items were dominated by pieces of film (70% in number). Microplastics in the size interval from 2.5 to 4.0 mm represented half of the total identified items. Small fragments in Guadalquivir River comprised most of the plastic mass input to the sea. Our results support the relevance of fragmentation processes inland, and the role of rivers and estuaries as sources of microplastics to the ocean.</p>

Nanocluster Growth and Coalescence Modulated by Ligands

We describe a model of nanocluster formation that incorporates competition between ligand adsorption and nanocluster growth. Growth occurs through the addition of a metal-ligand complex and coalescence of nanoclusters. The competition between ligands for binding sites on the nanoclusters and growth of the nanoclusters through coalescence creates interesting growth pathways. The patterns are reminiscent of those observed in the synthesis of gold thiolate nanoclusters. For a particular set of rate coefficients, described herein, we observe the formation of a kinetically stable nanocluster that participates in coalescent growth. This determines the size interval of the resulting nanoclusters in the size distribution. The kinetically stable cluster can be tuned by modifying the functional form of the number of surface sites on the nanoclusters, thereby changing the growth pathway and the final sizes of the clusters.

Nanocluster Growth and Coalescence Modulated by Ligands

We describe a model of nanocluster formation that incorporates competition between ligand adsorption and nanocluster growth. Growth occurs through the addition of a metal-ligand complex and coalescence of nanoclusters. The competition between ligands for binding sites on the nanoclusters and growth of the nanoclusters through coalescence creates interesting growth pathways. The patterns are reminiscent of those observed in the synthesis of gold thiolate nanoclusters. For a particular set of rate coefficients, described herein, we observe the formation of a kinetically stable nanocluster that participates in coalescent growth. This determines the size interval of the resulting nanoclusters in the size distribution. The kinetically stable cluster can be tuned by modifying the functional form of the number of surface sites on the nanoclusters, thereby changing the growth pathway and the final sizes of the clusters.

Nanocluster Growth and Coalescence Modulated by Ligands

We describe a model of nanocluster formation that incorporates competition between ligand adsorption and nanocluster growth. Growth occurs through the addition of a metal-ligand complex and coalescence of nanoclusters. The competition between ligands for binding sites on the nanoclusters and growth of the nanoclusters through coalescence creates interesting growth pathways. The patterns are reminiscent of those observed in the synthesis of gold thiolate nanoclusters. For a particular set of rate coefficients, described herein, we observe the formation of a kinetically stable nanocluster that participates in coalescent growth. This determines the size interval of the resulting nanoclusters in the size distribution. The kinetically stable cluster can be tuned by modifying the functional form of the number of surface sites on the nanoclusters, thereby changing the growth pathway and the final sizes of the clusters.

Grain Size-Related Strengthening and Softening of a Precompressed and Heat-Treated Mg–Zn–Ca Alloy

The impact of precompression, thermal treatment and its combination on the deformation behaviour of an extruded Mg–Zn–Ca (ZX10) alloy was studied with respect to a varied average grain size. The Hall–Petch plot was used to highlight the impact in a wide grain size interval. The initial texture of the wrought alloy was characterized by X-ray diffraction. Moreover, the evolution of microstructure and texture was provided by the electron backscatter diffraction (EBSD) technique. The obtained results indicate the strong contribution of deformation-thermal treatment on the resulting deformation behaviour. Particularly, after precompression and heat treatment, higher strengthening effect was observed in the reversed tensile loaded compared to compressed samples without any change in the Hall–Petch slope throughout the grain size interval. Unlike this strengthening effect, a reversed tension–compression yield asymmetry with higher strength values in compression has been obtained.