Two-dimensional Approach Research Articles

Modelling laminar diffusion flames using a fast convergence three-dimensional CVFEM code

Laminar diffusion flames have been employed extensively to investigate the effects of physical and chemical-related parameters on combustion phenomena. Attention has been given to improve combustion models while keeping the two-dimensional (2D) axisymmetric approach and simplified boundary conditions. The flow structure due to the discrete jet nature of the reactants claims a more realistic inlet boundary condition for the burner plate which can only be accomplished if the solution domain is 3D. In this work, we present a novel 3D simulation code for the analysis of non-premixed laminar flames of methane and air, considering detailed inlet boundary conditions. The code is based on the control volume finite element method, written in MATLAB environment. To accomplish that a novel flow-oriented upwind scheme was implemented for the advection terms of the conservation equations. Combustion modelling can be carried out by either an enhanced flame sheet model in which an enthalpy equation is integrated in combination with the mixture fraction equation or detailed reaction schemes. Radiative heat losses were accounted for in the added energy equation. Three-dimensional numerical predictions, based on the flame sheet model, were able to simulate the near-wall gas temperature and inflow velocity field of a set of perforated plate burner with different porosities. It was found that the discrete nature of the injection of fuel and oxidiser, inflow boundary condition, plays a significant role on flame shape and length. Much better agreement between published experimental data and numerical predictions was obtained, particularly regarding flame structure, species mass fractions and temperature distribution of non-premixed laminar flames regardless of the adopted simplified combustion model. It was observed that flame length decreased as the burner porosity increased, up to a certain limit. The modified flow-oriented scheme greatly improved solution stability and computational time of the reacting system predictions.

Physiological and proteomics analyses reveal the resistance response mechanism to alkali stress in the early seedlings (cotyledons vs. roots) of castor plant (Ricinus communis L.)

Soil alkalinity is a major environmental problem influencing plant growth and productivity in northeastern China. Castor plant (Ricinus communis) is one of the most important oilseed crops worldwide, and has good salt tolerance. The early seedling stage is extremely vulnerable to abiotic stresses, but little is known about the physiological and molecular mechanisms involved in the cotyledons and roots of castor seedlings under alkali stress. In this study, biomass, photosynthesis, root vitality, inorganic ions, organic solutes and antioxidant enzyme activities were measured. Two-dimensional gel electrophoresis-based proteomic approaches were also applied to identify differentially abundant proteins in alkali-treated seedlings. The results showed that alkali stress strongly inhibited seedling growth, especially of the roots. Na+ content increased with increasing alkalinity, and the roots had much higher Na+ and lower K+ than cotyledons. The proline and soluble sugars were both increased in cotyledons, but kept unchanged in the roots under alkali stress. Moreover, proteomic analysis revealed a total of 15 and 25 alkali-responsive proteins in the cotyledons and roots, respectively. For cotyledons, most of the identified proteins were involved in photosynthesis, stress and defense (＞10 %), while those for roots were mainly involved in carbohydrate and energy metabolism, genetic information, stress and defense (＞10 %). These results suggest that cotyledons and roots respond differently to alkali stress. Cotyledons retain efficiency of photosynthetic electron transport and accumulation of osmolytes, while the roots enhance transfer efficiency of the mitochondrial electron transport chain, adjust fatty acid biosynthesis, and promote phosphatidic acid biosynthesis under alkali stress. Additionally, the co-increased abundance of chaperonins indicated that both cotyledons and roots maintained folding of proteins into their proper 3D structures in response to alkali stress. These findings provide new insights into different physiological mechanisms in cotyledon and root responses to alkali stress during the early seedling stage in castor.

Hereditary Optic Neuropathies: Induced Pluripotent Stem Cell-Based 2D/3D Approaches.

Inherited optic neuropathies share visual impairment due to the degeneration of retinal ganglion cells (RGCs) as the hallmark of the disease. This group of genetic disorders are caused by mutations in nuclear genes or in the mitochondrial DNA (mtDNA). An impaired mitochondrial function is the underlying mechanism of these diseases. Currently, optic neuropathies lack an effective treatment, and the implementation of induced pluripotent stem cell (iPSC) technology would entail a huge step forward. The generation of iPSC-derived RGCs would allow faithfully modeling these disorders, and these RGCs would represent an appealing platform for drug screening as well, paving the way for a proper therapy. Here, we review the ongoing two-dimensional (2D) and three-dimensional (3D) approaches based on iPSCs and their applications, taking into account the more innovative technologies, which include tissue engineering or microfluidics.

Two-dimensional integration approach to teaching cardiovascular physiology: effectiveness and students\u2019 perspectives

BackgroundPre-clerkship medical curriculums consist of a series of organ system-based courses and lectures but often lack an integration between organ systems. Such integration could be beneficial for clerkship years and students’ future career. Hence, we aimed to share our process of organising an integrative teaching approach in a large class of pre-clerkship medical students and to reflect the students’ perspective toward the teaching process in this observational study. In addition, we tested effectiveness of this integrative approach compared with the traditional teaching (lecture).MethodsWe organised a two-dimensional (2D)-integrative teaching for 309 students in selected topics of cardiovascular physiology of the medical curriculum of the Faculty of Medicine, Chulalongkorn University, Thailand. The first dimension of integration is the incorporation of physiology of other organ systems into the cardiovascular physiology class. The second is the integration of multiple teaching methods and strategies, including small group discussion, student presentation, wrap-up, quiz, and question-and-answer sessions. Unless opting out, students evaluated this integrative teaching by filling in a questionnaire. The summative scores were also used to determine their comprehensive understandings of the content.ResultsThe course evaluation showed that most students (81.9–91.2%) had positive attitudes toward all organised sessions, i.e. this teaching method helps promote their basic and applied physiology knowledge, critical thinking, information searching, presentation, and teamwork skills. In general, students at all performance levels attained higher scores in the summative exam for the 2D-integrative-class–relevant questions (74.4±16.1%) than for the lecture-pertinent questions (65.2±13.6%).ConclusionsIn a large class size of pre-clerkship students, 2D-integrative teaching strategies with careful planning and preparation can be successfully implemented, based on positive attitudes and relatively high summative scores of students in this study. Hence, this comprehensive teaching could be incorporated in current medical curriculums, particularly for the complex learning topics.

Evaluation of potassium glycinate, potassium lysinate, potassium sarcosinate and potassium threonate solutions in CO2 capture using membranes

The mitigation process of greenhouse gases emission such as CO2 into the atmosphere is known as a vital necessity in modern societies. Nowadays, amino acid salt solutions (AASSs) have been extensively applied as a promising alternative to alkanol amine absorbents to increase the CO2 sequestration efficiency from disparate gaseous flows. This article aims to computationally and theoretically evaluate the CO2 separation percentage using potassium glycinate (PG), potassium lysinate (PL), potassium sarcosinate (PS) and potassium threonate (PT) amino acid solutions from an inlet gaseous mixture inside a hydrophobic membrane contactor (HMC). To do this, the governing first principal equations inside the HMC are solved using the computational fluid dynamics procedure based on finite element technique. Acceptable agreement between the simulation results and experimental values with average deviation of approximately 3% implies the validation of developed two-dimensional (2D) simulation approach developed in this study. The analysis of obtained results demonstrated that PG is the most efficient amino acid solution for CO2 molecular sequestration with the ability of separating 90% of inlet CO2 in the system. The order of solutions is 90% sequestration using PG > 89.3% sequestration using PT > 77.4% sequestration using PL > 72.3% sequestration using PS.

Study on Precise Satellite Attitude Maneuvering Strategy for Ultrahigh Resolution Spaceborne SAR Imaging

For future ultrahigh resolution spaceborne synthetic aperture radar (SAR), it requires the antenna beam capable of large angle scanning in azimuth to increase the azimuth bandwidth and to improve the resolution consequently. To achieve this goal, this paper proposes for the first time a complete implementation scheme based on three-axis attitude maneuvering of satellite platform. Starting from the determination of rotation center, we will deduce the variation of Euler angles during the whole imaging period. Compared with two-dimensional electronical beam-sweeping approach used in phased-array antenna, the most notable advantage of our approach is that it can guarantee azimuth Doppler frequency barely vary along the range line at any azimuth squint angle, which enables the effective decoupling of the signal in azimuth from that in range. Taking advantage of this characteristic, the processing efficiency of high resolution SAR imaging could then be improved to a great extent. Simulation results are presented to verify its effectiveness as well as superiority compared to electronical beam-sweeping.

Design and testing of additively manufactured high-efficiency resistojet on hydrogen propellant

This paper presents the design methodology and performance testing of an additively manufactured resistojet operating on hydrogen as propellant. Additive manufacturing allows to produce complex monolithic resistors, resulting in reliable high efficiency thrusters. The concept, to be used in combination with advanced cryogenic storage technologies, is proposed for short time and high specific impulse orbit transfers. The simplified two-dimensional thermal design approach adopted is discussed, and its application to the engineering of the resistor is shown for both Inconel 718 and tungsten. The paper reports the performance testing of the proof-of-concept version of the thruster, manufactured in Inconel 718. Experiments on hydrogen show near ideal performance, demonstrating a peak thermal efficiency of 96%. The thruster proves the validity of the design methodology proposed, and the feasibility of the approach to develop monolithic additively manufactured hydrogen resistojets as main propulsion units.

Kinematic and dynamic analysis of dam break flow impact on vertical walls using weakly compressible SPH

This article presents the kinematic and dynamic analysis of a dam break flow based on data obtained from numerical solutions by the smoothed particle hydrodynamics (SPH) method. The method and original algorithms necessary for correct pressure evaluation are thoroughly described. The pressure evaluation method consists of data reading using virtual sensors and filtration in the time domain using the weight function. A simple convergence study showing the independency of the evaluated parameters of spatial resolution is presented together with validation of the introduced methods and algorithms using a simple hydrostatic problem and experimental data available in the literature. We focus on two parameters that describe the problem: distance of the downstream vertical wall from the edge of the liquid column and the column’s height to width ratio. We found that the impact can be divided into three consecutive phases characterized by specific kinematic (flow patterns) and dynamic (exerted pressure and forces) behavior and different roles of the investigated parameters during these phases. During the early stages of an impact, the column’s distance from the vertical wall plays a major role. A dependency between the column distance and the force peak in this stage was identified in the form of a power function. In the second stage, when a rolling wave emerges, the vertical wall position influences the shape of the wave and the pressure distribution on the wall. The total force is greater in this phase for lower column height to width ratios due to the higher total momentum of the liquid. In the third stage, when the rolling wave impacts the liquid surface, the employed methodology with two-dimensional solution and free-surface approach seems to reach its limits of applicability. A more complex modelling would be necessary to capture this phase of the impact properly.

Value-based Performance Measurement with the Attribution Matrix and the Finite Change Sensitivity Index

We present a model of performance measurement and attribution for delegated investments that summarizes the manager effect and the client effect on value creation. In particular, we introduce an innovative two-dimensional approach that, on one hand, detects the (manager and client) decision effects, measuring the impact of manager/investor choices on the overall investment performance and, on the other hand, detects the (manager and client) period effects, measuring the impact of all the (manager and client) decisions on the investment performance in a given assessment interval. As for the decision effects, the value added of an active investment portfolio is broken down in terms of the value generated by the decisions made by the manager (manager decision effect) and the value generated by the client/investor (client decision effect). As for the period effects, we quantify the impact of all the decisions made in the assessment interval on the value creation generated in a single period by the manager (manager period effect) and the client (client period effect), so that the sum of the periods' attribution values is the investment's value added. In order to accomplish the task, we employ the Finite Change Sensitivity Index (FCSI), which enables one to quantify the impact of the most influential decisions made by manager and investor, and a truncation approach which is equivalent to the well-known residual-income approach. We then combine the two attribution dimensions into an Attribution Matrix (AM). Each element of the AM provides the amount of value added generated in a given period by the decisions made by the manager or by the investor in (the same or) another period.

A new approach to (key) keywords analysis: Using frequency, and now also dispersion

A widely-used method in corpus-linguistic approaches to discourse analysis, register/text type/genre analysis, and educational/curriculum questions is that of keywords analysis, a simple statistical method aiming to identify words that are key to, i.e. characteristic for, certain discourses, text types, or topic domains. The vast majority of keywords analyses relied on the same statistical measure that most collocation studies are using, the log-likelihood ratio, which is performed on frequencies of occurrence in two corpora under consideration. In a recent paper, Egbert and Biber (2019) advocated a different approach, one that involves computing log-likelihood ratios for word types based on the range of their distribution rather than their frequencies in the target and reference corpora under consideration. In this paper, I argue that their approach is a most welcome addition to keywords analysis but can still be profitably extended by utilizing both frequency and dispersion for keyness computations. I am presenting a new two-dimensional approach to keyness and exemplifying it on the basis of the Clinton-Trump Corpus and the British National Corpus.

Rapid wind–terrain correction for wildfire simulations

Modelling the propagation of wildfires requires an accurate wind field to correctly predict the behaviour of the fire. Although numerical weather prediction models produce reliable and accurate mesoscale forecasts, these are typically either available at a spatial resolution many times greater than the typical resolution of a wildfire model or a spot forecast that must be spatially interpolated to the area of the modelled wildfire. Due to this, these forecasts may not account for fine-scale terrain interactions with the wind and must be downscaled to a higher spatial resolution before use in a wildfire model. These downscaling methods are typically computationally intensive, limiting their use for situations where rapid predictions are required. Despite this, a three-dimensional mass balancing method is commonly used in wildfire prediction as a preprocessing step. In this study we show that this mass balancing method can be reduced to a two-dimensional approach, greatly reducing the complexity and computational time required for the model. The two-dimensional method is compared with the existing three-dimensional method and experimentally measured datasets. Furthermore, a combination of rapid numerical solution techniques and modern computational processors allow these wind–terrain correction methods to be directly incorporated into wildfire propagation models.

Primary and Secondary Loss of CO and NO Ligands in the Ultraviolet Photodissociation of the Heteroleptic Co(CO)3NO Complex.

The photodissociation dynamics of the heteroleptic Co(CO)3NO complex were investigated in the metal-to-carbonyl (CO) ligand charge-transfer band to compare the reactivity of the CO and nitrosyl (NO) ligands. The final state distributions of both the CO and NO fragments were measured using resonance-enhanced multiphoton ionization (REMPI) spectroscopy and velocity-map ion-imaging. The primary CO photofragment was differentiated from the secondary fragments of the subsequent unimolecular decomposition of coordinatively unsaturated intermediates by comparing the momentum distributions. The internal energy of the Co(CO)2NO intermediate was sufficiently high (≥348 kJ/mol) to be generated in the electronic excited state, indicating the occurrence of the primary CO elimination on an excited state. The NO fragments exhibited two velocity components. The analysis of the final state distributions suggested that the higher- and lower-kinetic-energy components originated from the direct primary elimination and sequential elimination, respectively. The direct photoelimination through a transiently bent ligand conformation was illustrated on the basis of a two-dimensional REMPI approach and time-dependent density functional theory calculations. The present results of both ligands demonstrate the correlation between elimination mechanisms and possible ligand conformations in the electronic excited state.

Integration of three-dimensional continuum model and two-dimensional bonded block model for studying the damage process in a granite pillar at the Creighton Mine, Sudbury, Canada

Bonded block model (BBM) has shown potential in replicating rock mass behavior as well as the rock–support interaction mechanism, but their practical application is limited to two dimensions due to the high associated computational demand. To allow for the use of BBM in simulating three-dimensional (3D) problems, this study proposes an integrated 3D continuum–two-dimensional (2D) discontinuum approach, in context of rock pillars. A cross-section of a granite pillar was simulated using a BBM with a load path from a calibrated mine-scale FLAC3D model. Pillar support as employed in the mine was also incorporated in different stages during the simulation. The model was calibrated by varying the input parameters until the displacements at six locations within the pillar matched those measured by a multi-point borehole extensometer (MPBX) in the field. The calibrated model was subsequently used to understand how the support and load path influenced the damage evolution in the pillar. The shear component of the load path was found to have a major effect on the severity and extent of the damaged regions. When the support density was increased in the model, the lateral displacements along the pillar walls were significantly suppressed in a somewhat unpredictable manner. This was explained by the interaction between the supports and the damaged regions at the corners, which ultimately modified the stresses along the pillar periphery. The amount of displacement reduction obtained by increasing the support density illustrates the potential of BBM to be used as a support design tool.

A new toolbox to distinguish the sources of spatial memory error.

Studying the sources of errors in memory recall has proven invaluable for understanding the mechanisms of working memory (WM). While one-dimensional memory features (e.g., color, orientation) can be analyzed using existing mixture modeling toolboxes to separate the influence of imprecision, guessing, and misbinding (the tendency to confuse features that belong to different memoranda), such toolboxes are not currently available for two-dimensional spatial WM tasks.Here we present a method to isolate sources of spatial error in tasks where participants have to report the spatial location of an item in memory, using two-dimensional mixture models. The method recovers simulated parameters well and is robust to the influence of response distributions and biases, as well as number of nontargets and trials.To demonstrate the model, we fit data from a complex spatial WM task and show the recovered parameters correspond well with previous spatial WM findings and with recovered parameters on a one-dimensional analogue of this task, suggesting convergent validity for this two-dimensional modeling approach. Because the extra dimension allows greater separation of memoranda and responses, spatial tasks turn out to be much better for separating misbinding from imprecision and guessing than one-dimensional tasks.Code for these models is freely available in the MemToolbox2D package and is integrated to work with the commonly used MATLAB package MemToolbox.

Influence of Erodible Beds on Shallow Water Hydrodynamics during Flood Events

Flooding has become the most common environmental hazard, causing casualties and severe economic losses. Mathematical models are a useful tool for flood control, and current computational resources let us simulate flood events with two-dimensional (2D) approaches. An open question is whether bed erosion must be accounted for when it comes to simulating flood events. In this paper we answer this question through numerical simulations using the 2D depth-averaged shallow-water equations. We analyze the effect of mobile beds on the flow patterns during flood events. We focus on channel confluences where water flow and sediment mobilization have a marked 2D behavior. We validate our numerical simulations with laboratory experiments of erodible beds with satisfactory results. Moreover, our sensitivity analysis indicates that the bed roughness model has a great influence on the simulated erosion and deposition patterns. We simulate the sediment transport and its influence on the water flow in a real river confluence during flood events. Our simulations show that the erosion and deposition processes play an important role on the water depth and flow velocity patterns. Accounting for the mobile bed leads to smoother water depth and velocity fields, as abrupt fields for the non-erodible model emerge from the irregular bed topography. Our study highlights the importance of accounting for erosion in the simulation of flood events, and the impact on the water depth and velocity fields.

A particle packing parallel geometric method using GPU

The purpose of this paper is to present a methodology for obtaining granular models from a GPU parallel implementation of the geometric separation particle packing strategy. This methodology is suitable for the generation of large-scale granular models used in discontinuous media simulations. The proposed approach uses disk-shaped particles (two-dimensional approach) and parallelization mechanisms that consider different computational environments, with a focus on GPUs. The methodology is divided into three macro-steps: (a) definition of an input set of particles; (b) geometric separation; and (c) removal of spurious particles. The set of input particles uses data related to the particle size distribution and the domain filling rate, defining arbitrary positions for the particles. The other steps are used to eliminate overlaps between particles. Parallel computing is performed using the OpenCL programming API on compatible devices. Examples are presented to show the effectiveness of the proposed methodology. They show good time improvement and better memory efficiency in comparison with the original serial version of the strategy. The method is also validated by comparing the results with experimental and numerical data from the literature. The proposed methodology allows generating granular models with a parallel GPU particle packing method. It turns possible the achievement of bigger models in a smaller amount of time, without compromising the strategy efficiency and accuracy. It also presents mechanisms to avoid information exchange between GPU and CPU.

Archaeobiogeography of extinct rice rats (Oryzomyini) in the Lesser Antilles during the Ceramic Age (500 BCE–1500 CE)

During the Ceramic Age (500 BCE–1500 CE), Lesser Antilles rice rats (Tribe Oryzomyini) made up a significant portion of the diet of Caribbean islanders. Archaeological excavations across the archipelago resulted to the discovery of large quantities of remains from to these now extinct taxa. It offers a unique opportunity to investigate the past biogeography of this taxon of high cultural and ecological importance. We have studied 1140 first lower molars originating from 40 archaeological sites across eleven islands of the Lesser Antilles archipelago using two-dimensional geometric morphometric approaches to establish spatiotemporal patterns relying on phenotypic variations. This study identified three morphological groups, present in all chrono-cultural periods, that were geographically restricted and consistent with published ancient mitochondrial DNA clusters. These three geographically-separate groups likely represent three distinct genera of rice rats. The first group includes specimens from the North of the archipelago (Saint-Martin, Saba, Saint-Eustatius, Saint-Kitts, and Nevis) and likely referable to as Pennatomys sp.; the second, occurring in the South (Martinique), is assigned to Megalomys desmarestii; and the third corresponds to specimens from the center of the Lesser Antilles (Antigua, Barbuda, Marie-Galante, and Guadeloupe) and likely corresponds to Antillomys sp. These oryzomyine morphotypes are present during all studied periods and support an older presence of these rodents in the region. Our results are congruent with ancient DNA studies that favor the hypothesis of a natural introduction of the group in the archipelago before settlement of human populations. Moreover, the observed phenotypic homogeneity and stability over the 2000 years of Pre-Columbian occupation suggests that rice rats were not part of long-distance inter-island exchanges by humans. Instead, rice rat human consumption was likely based on in-situ hunting of local populations.

Effects of rail transit on individual travel mode shares: A two-dimensional propensity score matching approach

We examine the impact of the opening of the Circle Line (CCL) in Singapore on individuals’ travel mode choice. Using data from cross-sectional surveys conducted before and after the CCL opening, we investigate how individuals’ travel mode choices changed in response to improved accessibility to the rail transit system. The difference-in-differences models show that the CCL opening increased the rail transit mode share and reduced the private car mode share. However, there was no significant impact on the mode share of buses or trip generation. We adopt a two-dimensional propensity score matching approach to adjust for spatial and temporal variations in the treatment and control groups. We find that the effect of the CCL on the promotion of rail usage is stronger in the matched sample model. This study provides new evidence that rail transit investments are effective in encouraging the switch from private cars to rail transit and thus reducing car dependency.

Experimental and CFD Study of Heat Transfer in Spouted Beds: Analysis of Nusselt Number Correlations

The application of CFD to evaluate heat transfer in spouted beds remains scarce. Furthermore, the few reported studies about this have used a correlation proposed to determine the Nusselt number for fixed and fluidized beds. Therefore, the aim of this work was to investigate the effects of the different correlations in describing heat transfer in a conical spouted bed, using a two-dimensional Euler-Euler approach. Correlations proposed specifically for a spouted bed were implemented by means of a user-defined function. The simulated fluid phase temperatures within the bed were compared with experimental data obtained for a spouted bed operating with sorghum seeds (Sorghum bicolor (L.) Moench). Correlations that take into consideration geometric parameters that are important in spouted bed design were implemented. The comparison among experimental and simulated data indicated the most suitable correlation for description of heat transfer in the spouted bed.

A Linear Brushless Direct Current Motor Design Approach for Seismic Shake Tables

The progress in material and manufacturing technologies enables the emergence of new research areas in electromagnetic actuator applications. Permanent magnet (PM) linear motors are preferred to achieve precise position control and to meet the need for high dynamic forces in the seismic shake tables that are used in analyzing reactions of structure models. The design approaches on the linear motors used in the seismic shake tables may vary depending on the desired force, stroke and acceleration values. Especially, the maximum width, the maximum depth, the maximum linear motor length in longitudinal direction and the maximum travelling distance parameters are the primary design criteria in seismic shake table drive systems. In this paper, a design approach for a linear PM brushless direct current (BLDC) motor with high force/volume, force/weight and force/input power ratios is developed. The design was analyzed using two-dimensional (2D) and three-dimensional (3D) finite element method (FEM) approaches through the ANSYS Maxwell software. The mathematically designed linear BLDC motor was manufactured and subjected to displacement, acceleration and force tests that are used in seismic analyses. The results of the experimental tests validate the convenience of the proposed design approach and the selected parameters.