Ring Distribution Research Articles

Structure and flow properties of coal ash slag using ring statistics and molecular dynamics simulation: Role of CaO/Na2O in SiO2–Al2O3–CaO–Na2O

Molecular dynamics simulation was applied to investigate the microstructure of slag in SiO2-Al2O3-CaO-Na2O system. A new structure model for slag was established through ring-statistics by MD simulation. The network structure was simplified into crosslinked rings divided into three types based on the ring size. The change of amorphous structure was well described by ring distribution. The destruction of slag structure by Ca2+ is more significant than Na+, and high CaO/Na2O resulted in low content of medium and large rings and low viscosity. The ring distribution coefficient (Rdc) was defined to establish the relationship between structure and viscosity: ŋ=26.7Rdc-10.2. When CaO/Na2O ratio increases, the ring distribution transforms from medium or high-order to low-order, leading to the decreasing of Rdc and slag viscosity. Moreover, CaO/Na2O ratio also changes the diffusivity of slag and thus the melting behavior. Finally, a linear relationship between the empirical liquidus temperature (Tliq) and atomic diffusivity from the MD simulations was obtained.

The formation and evolution of parent and oxygenated polycyclic aromatic hydrocarbons during a severe winter haze-fog event over Xi'an, China.

In this study, 3- or 4-h high time-resolved PM2.5 was observed during a severe winter haze-fog event (1 to 6 January 2017) to investigate the formation and evolution of parent polycyclic aromatic hydrocarbons (pPAHs) and oxygenated polycyclic aromatic hydrocarbons (OPAHs) in Xi'an, a typical city in northwestern China. Three episodes (episode I, episode II, and rainy day (EI, EII, and RD)) have been identified during this haze-fog event. Nine water-soluble ions, 8 carbonaceous fractions, 18 pPAHs, and 3 OPAHs in PM2.5 were measured. pPAHs showed two peaks at around 12:00 local standard time (LST) and 24:00 LST and two troughs at around 2:00 LST and 18:00 LST during EI. However, the OPAHs presented highest at around 18:00 LST and lowest at around 2:00 LST. During EII, pPAHs and OPAHs displayed similar diurnal variations with the highest values at noon but lowest values at around 2:00-5:00 LST.In addition, no obvious diurnal variations of pPAHs and OPAHs were observed during RDwere absent during RD. Diurnal variations of pPAH ring distributions demonstrated coal combustion, and vehicle emissions contributed to pPAHs for three episodes, which is further confirmed by diagnostic ratio results. High oxygenation (Ro) rates were found during the sampling time, which favored OPAH formation. The study herein indicates that OPAH formation through complex atmospheric reactions provides us new insights into the severe haze-fog events.

Influences of cooling rate on formation of amorphous germanene

In this work, we study thoroughly influences of cooling rate on the formation of two-dimensional (2D) germanene via molecular dynamics simulation using atomistic models composed of 10 4 atomic Ge atoms with the Stillinger - Weber potential. This influence is studied through the changes in the thermodynamic and structural properties of the model. We find that the relatively good quality amorphous germanene is formed at a cooling rate of 10 13 K s −1 with the glass transition temperature of 1210 K. The structural properties of 2D amorphous germanene are discussed through radial distribution function, coordination number, ring, interatomic-distance, and angle distribution. • We study thoroughly influences of cooling rate on the formation of two-dimensional (2D) germanene via molecular dynamics simulation. • We find that the relatively good quality amorphous germanene is formed at a cooling rate of 10 13 K s −1 with the glass transition temperature of 1210 K. • The microscopic structure of amorphous germanene is analyzed and discussed. • The differences between structural characteristics of germanene obtained at different cooling rates are compared.

Atmospheric concentration, source identification, and health risk assessment of persistent organic pollutants (POPs) in two countries: Peru and Turkey.

It is known that some persistent organic pollutants (POPs) are used worldwide, and these pollutants are dangerous for human health. However, there are still countries where measurements of these pollutants have not been adequately measured. Although many studies have been published for determining the concentrations of POPs in Turkey, there are limited studies in Latin American countries like Peru. For this reason, it is essential both to conduct a study in Peru and to compare the study with another country. This study is aimed at determining the atmospheric POPs such as polycyclic aromatic hydrocarbon (PAH), organochlorine pesticide (OCP), and polychlorinated biphenyl (PCB) concentrations using passive air samplers in Yurimaguas (Peru) and Bursa (Turkey). Molecular diagnosis ratios and ring distribution methods were used to determine the sources of PAHs. According to these methods, coal and biomass combustions were among the primary sources of PAHs in Peru, while petrogenic and petroleum were the primary sources of PAHs in Turkey. Then, α-HCH/γ-HCH and β-/(α+γ)-HCH ratios were used to determine the sources of OCPs. According to the α-HCH/γ-HCH ratios, the primary sources of OCPs in both countries were lindane. Similarly, according to β-/(α+γ)-HCH ratios, the HCHs have been historically used in Peru while they were recently utilized in Turkey. Finally, homologous group distributions were used to determine the sources of PCBs. Similar distributions of homologous groups were observed in the sampling sites in both countries. Also, the homologous group distributions obtained have been determined that industrial activities could be effective in the sampling areas in both countries. When the cancer risks that could occur via inhalation were evaluated, no significant cancer risk has been determined in both countries.

Particle‐in‐Cell Simulation of Rising‐Tone Magnetosonic Waves

AbstractRecent observations have reported that magnetosonic waves can exhibit rising‐tone structures in the frequency‐time spectrogram. However, the generation mechanism has not been identified yet. In this paper, we investigate the generation of rising‐tone magnetosonic waves in the terrestrial magnetosphere using 1‐D particle‐in‐cell (PIC) simulations, in which the plasma consists of three components: cool electrons, cool protons and ring distribution protons. We find that the magnetosonic waves excited by the ring distribution protons can form a rising‐tone structure with frequency of the structure ranging from about 0.5Ωlh to nearly Ωlh, where Ωlh is the lower hybrid frequency. It is further demonstrated that the rising frequency of magnetosonic waves can be accounted for by the scattering of ring distribution protons. Moreover, the rising‐tone timescale obtained by PIC simulation is compared with the satellite observation. Our findings provide some new insights to understand the nonlinear evolution of plasma waves in the Earth's magnetosphere.

Transient swelling behavior of the bovine caudal disc

The intervertebral disc is an avascular composite structure, comprised of the nucleus pulposus (NP) and the annulus fibrosus (AF). Previous tissue-level experiments either examined relative differences in swelling capacity of the two disc regions at a single time point or tested explant structures that did not replicate in situ boundary conditions. Previous joint-level studies that investigated time-dependent fluid flow into the disc provided limited information about swelling-induced intradiscal strains with respect to time and boundary constraints. Therefore, the objective of this study was to investigate time-dependent swelling behavior of the intervertebral disc ex situ. The first study investigated time-dependent free-swelling response of the whole disc and the disc's subcomponents separately (i.e., NP and AF). Findings from this study showed that the swelling rate and swelling capacity of NP explants under free-swelling conditions were greater than AF explants. The second study evaluated the effect of boundary conditions on in-plane strain distributions of intact discs and AF rings. Swelling-induced strain was highly heterogeneous in AF rings, where negative circumferential strains were observed in the inner AF and tensile circumferential strains were observed in the outer AF. Radial strains in AF rings were an order of magnitude greater than circumferential strains. Restricting fluid flow only to the outer AF periphery reduced the swelling of the inner AF. Swelling of intact discs affected both NP and AF swelling behaviors, where NP hydration decreased by 60%. Furthermore, the presence of the NP reduced peak radial strains in the AF and resulted in uniform strain distribution throughout the AF. In conclusion, these studies highlight that tissue hydration and swelling-induced strains largely depend on regional biochemical composition and geometric boundary constraints.

Sperry’s packing rule affects the spatial proximity but not clustering of xylem conduits: the case of Fagus sylvatica L.

Abstract Sperry’s packing rule predicts the optimum packing of xylem conduits in woody plants, where the frequency of xylem conduits varies approximately inversely with the square of the conduit radius. However, it is well established that such anatomical disposition does not remain fixed but is subject to a suite of adaptations induced by physiological constraints driven by both ontogenetic development and environmental characteristics. Here we challenge the hypothesis that increasing frequency of xylem conduits, concomitant with the decrease in their lumen area along the xylem pathway, would affect the spatial distribution of vessels inside tree-rings and their aggregation. To this end, we measured the vessels’ anatomical characteristics inside each tree-ring along with a complete radial series taken at different stem heights of Fagus sylvatica L. trees. Point pattern analysis indicated a significant effect of the distance from the tree base and a weak effect of cambial age on the nearest neighbour distance among xylem vessels, suggesting that vessels were closer to each other near the apex, and became progressively more distant toward the base. The spatial pattern of xylem vessels violated the assumption of complete spatial randomness, vessel spatial arrangement followed a uniform distribution at different distances from the tree base. Although there was an increase in the intensity and proximity among vessels, we demonstrated that no patterns of aggregation between vessels were found in sampled F. sylvatica trees. Rather, point pattern profiles clearly highlighted a lack of aggregation of vessels in the face of a regular spatial distribution in the annual growth rings along the stems.

Detailed Molecular Structure of Glassy Poly(phenylene oxide) (PPO) Studied by Molecular Dynamics Simulations

A modeling approach based on sequential stages of pressure compression (NPT) and constant volume (NVT) molecular dynamics (MD) simulations was used effectively for generation of models of glassy samples of poly(phenylene oxide) PPO. Starting from a large periodic simulation box the samples were brought down to the desired density using NPT simulations and also NVT simulations for energy and structural relaxation. The GROMOS 45a3 force-field, with appropriate intermolecular potentials for PPO, was used to model the interatomic interactions. The PPO glassy phase was studied by independently generating 9 samples with different numbers of chains (for the chains of repeat units 15, 25 and 40). Structural analysis included dihedral angle distribution, intra-chain and inter-chain radial distribution functions, radius-of-gyration and torsion angle distributions, free volume and the orientation distributions of intra-chain and inter-chain phenylene rings. The simulated solubility parameter was in excellent agreement with experimental data for PPO. This computational study of the glassy phase of PPO is an extension of earlier studies by others on single, unperturbed chains of PPO.

Stochastic Lagrangian dynamics of vorticity. Part 1. General theory for viscous, incompressible fluids

Abstract

Melts of nonconcatenated rings in spherical confinement.

Motivated by the chromosomes enclosed in a cell nucleus, we study a spherically confined system of a small number of long unknotted and nonconcatenated polymer rings in a melt and systematically compare it with the bulk results. We find that universal scaling exponents of the bulk system also apply in the confined case; however, certain important differences arise. First, due to confinement effects, the static and threading properties of the rings depend on their radial position within the confining sphere. Second, the rings' dynamics is overall subdiffusive, but anisotropic along the directions parallel and perpendicular to the sphere's radius. The radial center of mass displacements of the rings are in general much smaller than the angular ones, which is caused by the confinement-induced inhomogeneous radial distribution of the whole rings within the sphere. Finally, we find enhanced contact times between rings as compared to the bulk, which indicates slow and predominantly coordinated pathways of the relaxation of the system.

Power Flow Analysis and Optimization in Ring Distribution Network of Bahawalpur using Newton Raphson Method

Background: The primary motive of an electrical power system is to generate and supply electric power efficiently and reliably to the consumer-end. Transmission losses, system instability and increasing cost in proportion to demand are the main challenges faced in this process. Power flow analysis is required to robustly predict the active / reactive power within the buses, voltage magnitude / phase angles at each bus, cost of transmission and losses well before the practical installation of the power network. Methods/Statistical Analysis: In this paper, we employ power flow analysis using Newton Raphson method and Fast Decoupled method to minimize cost of the electricity and finding optimum active and reactive powers without affecting the voltage regulation. The power flow algorithms are applied for solving the aforementioned load flow problem for ring distribution network of Bahawalpur. We carried out the modeling by obtaining realistic data for constructing bus admittance matrix and specifications of generation units and loads which are connected at the buses. Findings: As a result, optimum flow of power along with the voltage values among different regions of Bahawalpur is obtained. The results from both the algorithms successfully converge and there is an absolute match to validate the accuracy. Novelty: These novel results are of paramount importance since the proposed architecture of Bahawalpur is ring distribution network to replace the existing radial network for improved performance. Furthermore, this research will pave the way for power system planning of Bahawalpur region where all the electrical parameters are known beforehand to design the components according to the requirement. Keywords: Electric power system; voltage magnitude; phase angle; power flow analysis; Newton Raphson method; ring distribution network; active power; reactive power

Conceptual model framework for demand response ancillary services deployed by inter-connected microgrids in West Africa – A Nigerian case study

As a result of the poor electrification rate in many Sub-Saharan countries, several researches have been geared towards the adoption of distributed generation resources (in micro-grids) as a means to ameliorate this menace. For substantial ancillary services rendered, multiple micro-grid operators need to participate in the capacity and energy market. A conceptual framework model is presented in this paper where four distinct microgrids within rural communities are inter-linked and provide ancillary services to one another in the case of a capacity outage in any one of the other microgrids. The Microgrid Ancillary Service Operator (MASO) is in charge of managing the ancillary service which will accept bids from demand response aggregators, and then perform an optimal power flow to allocate capacities (energy resources) to meet demands in a day-ahead or hour-ahead time frame. The techno-economic analysis and distribution network design for one of the micro-grids considered was performed for a typical rural community in a Nigeria which had a residential and commercial load of 551 kWh/day and 23 kW h/day respectively. Results from HOMER showed an optimal system combination of 350 kW solar PV, 150 kW diesel generator, 300 units of Surrette 4KS25 P battery (having a usable nominal capacity of 1368 kW h), and a 100-kW converter. Also, using voltage drop constraints, the analytical design for a 3-bus ring distribution network which comprised a main feeder, and two load buses produced appropriate wiring sizes alongside commensurate resistance and reactance parameters which were within the permissible voltage limits set.

Paraspinal structures of thermoregulation

A detailed analysis of the literature on the structure and functions of the paraspinal structures of human thermoregulation involved in maintaining temperature homeostasis is presented. It is shown that in the process of evolution, a peculiar paraspinal morphofunctional complex is formed around the spinal center of thermoregulation, including thermal- generating structures (adipose and muscle tissue); venous thermal distribution rings formed by paraspinal venous plexuses and thermoregulatory nervous apparatus (meningeal and posterior branches of the spinal nerves and their nerve endings). It was found that the heat-generating structures are represented by adipose tissue of the epidural space, adipose tissue of the bone marrow, paravertebral and interscapular adipose tissue, back muscles and intercostal muscles). Bone marrow fatty tissue plays an important role not only in thermoregulation, but also in bone remodeling. Fatty tissue mainly includes components of white and a small amount of brown adipose tissue. Heat from muscles through the venous system of the spinal column affects the functioning of the spinal center of thermoregulation by contractile thermogenesis. It has been shown that around the center of thermoregulation of the spinal cord, venous vessels form four thermal distribution rings. The first of them is the venous bed of the soft membrane of the spinal cord and cerebrospinal fluid of the subarachnoid space; the second is the internal vertebral venous plexus; the third - intraosseous (intraorgan) venous plexuses of the vertebrae; the fourth is the anterior and posterior external vertebral venous plexuses. All four thermal distribution venous rings anastomose among themselves, forming a single thermal distribution system around the spinal center of thermoregulation. The innervation of thermal generating structures and thermal distribution of venous rings is carried out by somatic and autonomic nerve fibers.

Mechanical–thermal sequential coupling simulation for predicting the temperature distribution of seal rings – Part II

Understanding the running status of a mechanical seal – including its thermal state – is critical to ensuring the long service life of rotating machinery. Published in two instalments, this article broadly covers failure analysis of mechanical seals. In particular, it presents details of an approach to predicting the temperature distribution of seal rings using mechanical–thermal sequential coupling simulation. Three different cases are studied for comparison purposes in order to reveal the effect of misalignment on the thermal state.

Triphenylantimony(V) Catecholates Based on 3,6-Di-tert-Butyl-2,5-Dihydroxy-1,4-Benzoquinone

2,5-Dihydroxy-3,6-di-tert-butyl-p-benzoquinone (QtBuDiol) reacts with Ph3SbBr2 in toluene in the presence of triethylamine to yield the ionic complex [Et3NH]+[(DionetBuDiolate)SbPh3Br]– (I). The same reaction in methanol leads to complete displacement of bromide ions from the antimony coordination sphere and gives triphenylantimony(V) 1,2-diolate (DionetBuDiolate)SbPh3 · MeOH (II · MeOH). The molecular structure of the complexes was determined by X-ray diffraction (CIF files CCDC no. 1960681 (I · toluene) and 1960682 (II · 2MeOH)). Both complexes are characterized by quinoid bond distribution in the six-membered carbon rings and by C=O double bonds in the Ph3SbO2C6(t-Bu)2O2 moieties. Formally, the complexes can be considered as 3,6-di-tert-butyl-o-benzoquinone derivatives with the organometallic Ph3SbO2 group in positions 4 and 5 of the quinone ring. The electrochemical reduction of II · MeOH in dichloromethane occurs at E1/2 = –1.52 V, which is significantly shifted to the cathodic region relative to the data for 3,6-di-tert-butyl-o-benzoquinone (E1/2 = –0.51 V). This redox potential shift indicates a significant decrease in the electron-withdrawing properties of the o-quinoid moiety, which is caused by the effect of the electron-donating catecholate metallacycle.

First Observations of Magnetosonic Waves With Nonlinear Harmonics

AbstractMagnetosonic waves, with the frequency between proton cyclotron frequency and lower hybrid frequency, mainly occur near the Earth's magnetic equatorial plane and play an important role in the magnetospheric dynamics. In this paper, we report unusual magnetosonic waves with nonlinear harmonics observed by Magnetospheric Multiscale mission in the magnetotail. These magnetosonic waves have multiband enhanced electromagnetic power spectral densities (Bw/B0 up to 1/45) with the frequency from below to above the lower hybrid frequency and are quasi‐perpendicular propagating and linearly polarized. The frequency of the fundamental band is much higher than the proton cyclotron frequency fci (i.e., ~35 fci). We identified these emissions as high‐frequency magnetosonic waves with nonlinear harmonics. These are the first observations of such high‐frequency magnetosonic waves with the frequencies of harmonics higher than the lower hybrid frequency in the Earth's magnetosphere to the best of our knowledge. Given the absence of ring distributions for the protons and the easy coupling between compressed mode and its electromagnetic term, we propose that these nonlinear harmonic structures of the observed magnetosonic waves are likely generated by the nonlinear wave‐wave coupling among electromagnetic terms of the fundamental and higher harmonic waves.

Hydrogen peroxide oxidation degradation of a low-rank Naomaohu coal

A mild controllable oxidation method was developed to depolymerize the macromolecular aromatic clusters of NMH coal into water-soluble products (WSPs) without ring-open reaction. Hydrogen peroxide (H2O2) was employed to oxidize coal sample at 60 °C, and the effect of reaction time on coal conversion and oxidation products was studied. The results showed that H2O2 is able to break bridge bonds and side chains connected to aromatic clusters, while Car-Car bonds of arene keep unchanged at same conditions. After 10 h oxidation, the coal conversion is 83.4 wt% and the aromaticity of oxidation residue is 7.43%, indicating most of aromatics have transferred to WSPs. The aromatic ring distribution in WSP can reflect that of NMH coal to some extent, where 1-ring, 2-ring and 3-ring compounds account for 58.4 mol%, 19.9 mol% and 21.7 mol%, respectively. Moreover, the pyrolysis of NMH coal and oxidation residue was conducted on an online pyrolysis-vacuum ultraviolet photoionization mass spectrometry, and the oxidation of several typical model compounds was also carried out to understand the oxidation mechanism. The results showed that the PhO-RPh bonds between aromatic clusters are most easily destroyed by H2O2. H2O2 oxidation degradation of coal are accompanied by generation of alkenes and decarboxylic reaction.

Mechanical–thermal sequential coupling simulation for predicting the temperature distribution of seal rings – Part I

Understanding the running status of a mechanical seal – including its thermal state – is critical to ensuring the long service life of rotating machinery. Published in two instalments, this article broadly covers failure analysis of mechanical seals. In particular, it presents details of an approach to predicting the temperature distribution of seal rings using mechanical–thermal sequential coupling simulation. Three different cases are studied for comparison purposes in order to reveal the effect of misalignment on the thermal state. The first part of this article, which appears here, mainly describes the computational approach and the coupled numerical method, including the mechanical and thermal models, and the friction power-distribution for the load transformation. The second instalment will be published in the June 2020 issue of Sealing Technology.

Wave Normal Angle Distribution of Magnetosonic Waves in the Earth's Magnetosphere: 2‐D PIC Simulation

AbstractRadiation belt electrons can be accelerated and scattered by magnetosonic waves in the Earth's magnetosphere, and the scattering rate of electrons is sensitive to the wave normal angle. However, observationally it is difficult to identify the wave normal angle within a few degrees. In this study, using 2‐D particle‐in‐cell (PIC) simulations, we investigate the wave normal angle distribution of magnetosonic waves excited by ring distribution protons. Both the linear theory and simulations have shown that the wave normal angles are distributed over a narrow range (82°–89°) with a major peak at about 85° during the linear growth stage when the proton ring velocity is close to the Alfven speed. In addition, 2‐D PIC simulations further demonstrated that the waves tend to have larger wave normal angles (84°–89°) during the saturation stage since the waves with smaller wave normal angles are dissipated faster. It is also found that wave normal angles decrease with the increase of wave frequency. With the increase of the ring velocity of the proton ring distribution, the perpendicular wavenumber of excited magnetosonic waves decreases, which leads to the decrease of the wave normal angle. The simulation results provide a valuable insight to understand the property of magnetosonic waves, and the findings are useful for the global simulations of radiation belt dynamics.

Investigation of countercurrent flow profile and liquid holdup in random packed column with local CFD data

Liquid holdup and mass transfer area are critical parameters for packed column design and CO2 capture efficiency prediction. In this paper, a framework was established for modeling the liquid–gas countercurrent flow hydrodynamics in a random packed column with pall rings. Besides the column-averaged information, the radial pall ring distribution, velocity, and liquid holdup profiles are obtained to study the entrance effect and the wall influence in the packed column. With local CFD data, the validated packing specific area ap and liquid velocity uL range for liquid holdup correlation is significantly expanded with respect to existing experimental or column-averaged CFD data. The proposed liquid holdup correlation hL~uL0.44 indicates the random packed column falls in a viscous to turbulent transition regime and it covers a Reynolds Number range of [6.7–40.2]. The derived liquid holdup correlation is in good agreement with existing correlations developed using the column-averaged experimental data.