Sweep Technique Research Articles

KEANEKARAGAMAN JENIS CAPUNG DI SEPANJANG SUNGAI AYUNG

This research was conducted from february to April 2020 in three different areas, including in Petang in Penikit Village, Sayan Village, Ubud, and in Padang Galak Village, Sanur using sweeping techniques. This study aims to determine the diversity of dragonflies along the Ayung river. The analyzes carried out include analyzing the Shannon-Wiener diversity index (H'), evenness index (E), dominance index (D) sympons, frequency of presence and water quality of the Ayung River. The results showed as many as 11 species of dragonflies. The most common individuals found were Orthetrum Sabina (23 individuals), while the lowest individuals were from the Libellulidae family as many as 5 individuals. Most species and individuals were found at the Sayan location with 11 species with a total of 124 individuals (H'=2.24, E=0.93, D=0.19), followed by 6 species in the Petang location with a total of 27 individuals (H' =1.60, E=0.89, D=0.30), while the lowest was the Sanur location with 4 species with a total of 15 individuals (H'=0.94, E=0.69, D=0.67 ). Diversity of dragonflies in the Ayung River is classified as moderate (H'=2.36), the evenness index of species at the Petang and Sayan locations is in the almost evenly distributed category. Petang (0.89) and Sayan (0.93), while the Sanur location was in the fairly even category (0.69). The highest frequency of presence in Orthetrum sabina species was 89% with frequent or absolute presence categories. The BOD and DO values ??in the Ayung River do not meet the requirements of water quality standards, while COD meets the requirements based on PP No. 82 of 2001.
 Keywords: Diversity, dragonflies, Ayung River.

An improved wild horse optimization algorithm for reliability based optimal DG planning of radial distribution networks

This paper introduces a novel technique for optimal distribution system (DS) planning with distributed generation (DG) systems. It is being done to see how active and reactive power injections affect the system’s voltage profile and energy losses. DG penetration in the power systems is one approach that has several advantages such as peak savings, loss lessening, voltage profile amelioration. It also intends to increase system reliability, stability, and security. The main goal of optimal distributed generation (ODG) is a guarantee to achieve the benefits mentioned previously to increase the overall system efficiency. For extremely vast and complicated systems, analytical approaches are not suitable and insufficient. Therefore, several meta-heuristic techniques are favored to obtain better performance from were convergence and accuracy for large systems. In this paper, an Improved Wild Horse Optimization algorithm (IWHO) is proposed as a novel metaheuristic method for solving optimization issues in electrical power systems. IWHO is devised with inspirations from the social life behavior of wild horses. The suggested method is based on the horse’s decency. To assess the efficacy of the IWHO, it is implemented on the 23 benchmark functions Reliability amelioration is the most things superb as a result of DGs incorporation. Thus, in this research, a customer-side reliability appraisal in the DS that having a DG unit was carried out by a Monte Carlo Simulation (MCS) approach to construct an artificial history for each ingredient across simulation duration. For load flow calculations, the backward Forward Sweep (BFS) technique has been employed as a simulation tool to assess the network performance considering the power handling restrictions. The proposed IWHO method has been measured on IEEE 33 69 and 119 buses to ascertain the network performing in the presence of the optimal DG and the potential benefits of the suggested technique for enhancing the tools used by operators and planners to maintain the system reliability and efficiency. The results proved that IWHO is an optimization method with lofty performance regarding the exploration–exploitation balance and convergence speed, as it successfully handles complicated problems.

Calibration method for an extended depth-of-field microscopic structured light system.

This paper presents a calibration method for a microscopic structured light system with an extended depth of field (DOF). We first employed the focal sweep technique to achieve large enough depth measurement range, and then developed a computational framework to alleviate the impact of phase errors caused by the standard off-the-shelf calibration target (black circles with a white background). Specifically, we developed a polynomial interpolation algorithm to correct phase errors near the black circles to obtain more accurate phase maps for projector feature points determination. Experimental results indicate that the proposed method can achieve a measurement accuracy of approximately 1.0 μm for a measurement volume of approximately 2,500 μm (W) × 2,000 μm (H) × 500 μm (D).

3D CVD N-Doped Graphene Coated Cu Foam As Electro-Catalyst Towards CO2 Reduction Reaction (CO2RR)

At present, carbon dioxide emission is a significant environmental problem and cause of global climate change. Therefore, the utilization and conversion of CO2 should be an integral part of carbon management. One of the promising approaches to convert this greenhouse gas into value-added or commodity products is an electrochemical reduction of carbon dioxide via a path of carbon dioxide reduction reaction (CO2RR). Nevertheless, CO2 is an inert molecule that requires more energy to activate the chemical bond. Moreover, the reduction of CO2 is a complex reaction due to many paths of electron transfers on the electrocatalyst surface. Generally, the conversion of CO2 reduction relates to the composition and structure of electrode, electrolyte solution, and experimental condition. Herein, we use N-doped graphene on copper foam (N-GP/CuF) as a catalyst prepared by CVD process. To understand the electrochemical performances of synthesized catalyst for CO2 reduction, we electrochemical characterized by using linear sweep (LSV) and gas chromatography (GC) techniques. The nitrogen doped on the few-layer graphene catalyst not only reduces the onset potential but also improves the current density. These benefits help opening the new perspective in the field of electrochemical conversion of CO2 catalyst.

Towards Realizing High-Voltage Aqueous Zinc Batteries: An Investigation of the Zinc Anode in Concentrated Acetate-Based Electrolytes

Zinc-based aqueous battery systems are attractive for grid storage applications due to the inherent electrolyte safety, material non-toxicity, low cost, high volumetric capacity of zinc and the low polarizability of the zinc anode in aqueous solutions. Despite these key features, they possess lower energy density when compared to lithium-ion batteries primarily due to the limited working potential range for aqueous electrolytes. In addition, zinc hosts a slew of problems such as inhomogeneous material distribution upon cycling and the formation of inactive zinc species and dendrites, all of which contribute to capacity loss and ultimately, cell failure. Water-in-salt electrolytes (WiSE) have been found to be an effective strategy to expand the electrochemical window of aqueous electrolytes for high energy density aqueous-based batteries, including zinc batteries. There is a growing amount of literature on highly concentrated acetate-based electrolytes as low-cost and non-toxic WiSE for lithium, potassium, sodium and magnesium and zinc battery systems. However, work is scarce on the nature of zinc electrochemistry, morphology and reversibility in these concentrated electrolytes at realistic current densities (> 1 mA/cm2) and higher zinc utilization. Understanding the electrochemical behavior of zinc in this electrolyte system will significantly aid in the development of a high voltage zinc aqueous battery.In this work, the zinc electrochemical performance and surface morphology is studied in highly concentrated bi-salt potassium acetate (KOAc)-zinc acetate (Zn(OAc)2) electrolytes. The impact of the high concentration on the electrochemical working window of the electrolytes is measured using potential sweep and constant-current techniques. As the acetate concentration is varied from 1 m to 32 m, the largest electrochemical window is measured at 3.33 V for 31 m KOAc+ 1 m Zn(OAc)2. Zinc half cells are cycled at current densities of 1-5 mA/cm2 to examine zinc reversibility with respect to zinc depth-of-discharge (DOD) in these electrolytes. The zinc discharge product is visualized by in-operando optical microscopy as a function of the potential and is observed to be a zinc plating/stripping phenomenon in contrast to zinc dissolution/precipitation typically observed in alkaline media. Energy dispersive X-ray spectroscopy and X-ray diffraction studies display the minor presence of zinc oxide and zinc hydroxide after repeated cycling. Cloud point measurements are performed to measure the phase stability of these electrolytes at 5-25ºC as a function of acetate concentration, which show that concentrations below (and including) 27 m KOAc + 1 m Zn(OAc)2 does not induce crystallization at these temperatures. Preliminary measurements using spectroscopic techniques such as Raman and nuclear magnetic resonance (NMR) spectroscopy are conducted to elucidate ion solvation structures as a function of acetate concentration. Overall, the current and proposed studies are fruitful in understanding the relationship between zinc anode and the concentrated acetate-based electrolytes in the pursuit of a high-voltage aqueous zinc battery.

Magnetohydrodynamic thermal characteristics of water-based hybrid nanofluid-filled non-Darcian porous wavy enclosure: effect of undulation

PurposeThe aims of this study is to numerically investigate the thermal phenomena during magnetohydrodynamic (MHD) free convection in an oblique enclosure filled with porous media saturated with Cu–Al2O3/water hybrid nanofluid and heated at the left wavy wall. The thermophysical phenomena are explored thoroughly by varying the amplitude (λ) and undulation (n) of the wavy wall and the inclination of the enclosure (γ) along with other pertinent physical parameters. Darcy–Rayleigh number (Ram), Darcy number (Da), Hartmann number (Ha) and nanoparticle volumetric fraction (ϕ). The effect of all parameters has been analyzed and represented by using heatlines, isotherms, streamlines, average Nusselt number and local Nusselt number.Design/methodology/approachThe finite volume method is used to work out the transport equations coupled with velocity, pressure and temperature subjected to non-uniform staggered grid structure after grid-sensitivity analysis by an indigenous computing code and the semi-implicit method for pressure linked equations (SIMPLE) algorithm. The solution process is initiated following an iterative approach through the alternate direction implicit sweep technique and the tridiagonal matrix algorithm (TDMA) algorithm. The iterative process is continued until successive minimization of the residuals (<1e-8) for the governing equations.FindingsThis study reveals that the increase in the heating surface area does not always favor heat transfer. An increase in the undulation amplitude enhances the heat transfer; however, there is an optimum value of undulation of the wavy wall for this. The heat transfer enhancement because of the wall curvature is revealed at higher Ram, lower Da and Ha and lower volume fraction of nanoparticles. In general, this augmentation is optimum for four undulations of the wavy wall with an amplitude of λ = 0.3. The heat transfer enhancement can be more at the cavity inclination γ = 45°.Research limitations/implicationsThe technique of this investigation could be used in other multiphysical areas involving partial porous layers, conducting objects, different heating conditions, wall motion, etc.Practical implicationsThis study is to address MHD thermo-fluid phenomena of Cu–Al2O3/water-based hybrid nanofluid flow through a non-Darcian porous wavy cavity at different inclinations. The amplitude and number of undulations of the wavy wall, permeability of the porous medium, magnetic field intensity, nanoparticle volumetric fraction and inclinations of the enclosure play a significant role in the heat transfer process. This analysis and the findings of this work can be useful for the design and control of similar thermal systems/devices.Originality/valueMany researchers have examined the problem of buoyancy-induced free convection in a wavy-porous cavity packed with regular fluids or nanofluids. However, the effect of magnetic fields along with the amplitude (λ) at different undulations (n) of the heated wavy wall of an inclined enclosure is not attended so far to understand the transport mechanisms. Most often, the evolutions of the thermo-fluid phenomena in such complex geometries invoking different multiphysics are very intricate. Numerical implementations for simulations and subsequent post-processing of the results are also challenging.

Analysis of Flame Suppression Capabilities Using Low-Frequency Acoustic Waves and Frequency Sweeping Techniques

Symmetry plays a key role in the processing and analysis of not only visual but also acoustic signals in various multidisciplinary areas. New innovative and environmentally friendly methods for extinguishing flames are still being sought worldwide. One of these techniques appears to be the acoustic method. A laboratory stand was built for this purpose, which was coupled with the tested prototype of a high-power acoustic extinguisher, and then the original experiments and analyses of extinguishing effectiveness were carried out. For extinguishing, waveforms with specified parameters selected symmetrically around the frequency for which the extinguisher was designed were used. The aim of this article is to present and discuss selected measurement results concerning the possibility of flame extinguishing with the use of sinusoidal acoustic waves of low frequency (below 21 Hz), as well as with the use of frequency sweeping techniques with set parameters. Such an extinguisher can be equipped with an intelligent module so that the extinguisher may be activated automatically (without human intervention) when flames are detected. The benefits of this combination as well as the importance of image processing for flame detection are also presented in this paper. This solution, with its good fire detection and fast response, may be applicable for extinguishing firebreaks in particular.

Dynamical analysis of early afterdepolarization patterns in a biophysically detailed cardiac model.

Arrhythmogenic early afterdepolarizations (EADs) are investigated in a biophysically detailed mathematical model of a rabbit ventricular myocyte, providing their location in the parameter phase space and describing their dynamical mechanisms. Simulations using the Sato model, defined by 27 state variables and 177 parameters, are conducted to generate electrical action potentials (APs) for different values of the pacing cycle length and other parameters related to sodium and calcium concentrations. A detailed study of the different AP patterns with or without EADs is carried out, showing the presence of a high variety of temporal AP configurations with chaotic and quasiperiodic behaviors. Regions of bistability are identified and, importantly, linked to transitions between different behaviors. Using sweeping techniques, one-, two-, and three-parameter phase spaces are provided, allowing ascertainment of the role of the selected parameters as well as location of the transition regions. A Devil's staircase, with symbolic sequence analysis, is proposed to describe transitions in the ratio between the number of voltage (EAD and AP) peaks and the number of APs. To conclude, the obtained results are linked to recent studies for low-dimensional models and a conjecture is made for the internal dynamical structure of the transition region from non-EAD to EAD behavior using fold and cusp bifurcations and maximal canards.

Impact of pH on the Anodic Current-Voltage Characteristics of the Alkaline Cu ∣ Cu (II), Glycine System

Anodic voltammograms using rotating disc electrode (RDE) and linear sweep (LS) techniques were obtained for alkaline (9 < pH < 11.2) Cu (II)-glycine solutions. The nature and properties of the RDE anodic pseudo-limiting currents i lim and LS peak currents i p were considered within the framework of a theoretical model, taking into account the peculiarities of mass transfer of chemically interacting species. Both i lim and i p increase with solution pH and vary linearly with the concentration of glycinate anion l−. The degree of irreversibility of the process significantly affects the i p values, but has only small influence on i lim. Both characteristic current densities could serve as a measure of deprotonated ligand species, which is capable of forming stable Cu (II) complexes. The applications of modified equations, which were derived for i p in the case of simple redox systems, are discussed in detail.

Short-Term Strong Cathodic Polarization of Ni/YSZ and Pt/YSZ

The initial stages of YSZ reduction and formation of intermetallic phases at Ni∣YSZ interfaces on strongly cathodically polarized electrodes were studied by a number of potential sweep and impedance techniques. The measurements were carried out in the potential range −1.0 V to −3.0 V vs E°(O2) in H2/H2O at 650 and 750 °C. Below −1.7 V the cathodic current increases almost exponentially, mainly due to electronic conductivity in the YSZ. Reduction and oxidation peaks develop below and above −1.9 V, respectively. The peaks reveal a simultaneous reduction of YSZ at the Ni∣YSZ interface and reoxidation of a Ni-Zr phase. Charges calculated from the reoxidation peaks indicate a thickness of 200 nm for the layer formed by conditioning the electrode for 300 s at −2.6 V vs E°(O2). Impedance measurements show a suppressed arc decreasing with increasing polarization. Below −2.3 V vs E°(O2) a capacitive high frequency arc segment and an inductive low frequency loop develop. Both are ascribed to electronic conductivity. SEM/EDS microscopy on cross sections of samples cooled with and without polarization showed the formation of uniform and homogeneous intermetallic reaction layers which after reoxidation resulted in a two-phased nanostructures.

An improved backward/forward sweep power flow method based on network tree depth for radial distribution systems

This paper presents an improved load flow technique for a modern distribution system. The proposed load flow technique is derived from the concept of the conventional backward/forward sweep technique. The proposed technique uses linear equations based on Kirchhoff’s laws without involving matrix multiplication. The method can accommodate changes in network structure reconfiguration by involving the parent–children relationship between nodes to avoid complex renumbering of branches and nodes. The IEEE 15 bus, IEEE 33 bus and IEEE 69 bus systems were used for testing the efficacy of the proposed technique. The meshed IEEE 15 bus system was used to demonstrate the efficacy of the proposed technique under network reconfiguration scenarios. The proposed method was compared with other load flow approaches, including CIM, BFS and DLF. The results revealed that the proposed method could provide similar power flow solutions with the added advantage that it can work well under network reconfiguration without performing node renumbering, not covered by others. The proposed technique was then applied in Tanzania electric secondary distribution network and performed well.

Distributed Generation Effect on Distribution System

The idea about this proposed work, to know the Distributed Generation (DG) impact on distribution scheme. This is to improve the performance of the system using power loss reduction and voltage development. In this proposed work Wind Turbine (WT) and Photo-Voltaic (PV) units were taken for DGs and various algorithms are tested to get the effect of DG on network. In this paper one new hybrid algorithm is proposed to have optimal size and location of various types of DGs. Initially, active and reactive power losses of the test system and voltage at every bus of the test system were examined using Back and Forward (B/FW) Sweep technique. Similarly, Gravitational Search Analysis (GSA), BAT Analysis (BA) and Ant Lion Optimization (ALO) techniques were utilized to examine the parameters of the same test system. Finally, all the constraints were compared with projected hybrid approach. All the algorithms have tested on IEEE-33 and IEEE-69 standard test systems. Furthermore, the MATLAB simulation is used to get the optimal allocation of DGs.

The participatory turn in museums: The online facet

Social media platforms act as points of convergence for museums facing the pressure to adopt more sweeping participatory techniques. They are potentially powerful instruments in the “democratisation” process; yet the possibilities they offer in terms of spreading mass information do not automatically secure a higher level of online participation. This study uses the stimulus-organism-response (SOR) model to explore the different stimuli that museums with complex codes of access use to “democratise” themselves through the agency (organism) of social media, together with evaluating the effectiveness of their work on the basis of online public response. Empirically, the analysis was carried out in nine Italian State Archaeological Museums, as exemplars of museums with complex codes of access, with an investigation into the content of their Facebook posts and the interaction that these posts generated over more than a year. The results show, firstly, the diversity among the stimulus categories ranging from messages used to communicate and promote a museum's agenda to posts that dwell on its collection. In terms of online response, information about the museum's agenda is shown to be not sufficiently appealing to engage users online, while messages about the museum's core feature (its collections) are rewarded by its followers. These findings indicate that social media do not challenge the museums’ curatorship authority and can be an instrument for the museums’ dual mission to entertain and educate.

Voltammetric characteristics of smooth lead electrodes in sulfuric acid and TydrolyteTM solutions part 2. the Pb/PbSO4 potential region

The effects of 1.265 g•mL−1 Tydrolyte™ solution on the processes taking place on a smooth lead electrode were evaluated and compared to regular battery electrolyte in the Pb/PbSO4 potential region. At these potentials, cyclic voltammetry and potentiodynamic sweep techniques were used to simulate the conditions of a lead-acid battery negative plate. It was found that the potentials of lead oxidation and of lead sulfate reduction remained unchanged in the alternative electrolyte; however, the rate of formation and growth of lead sulfate was affected. For the Pb-Tydrolyte system, the rate of lead sulfate formation and growth was inhibited during the initial stages of cycling, but then increased and eventually became comparable to the Pb-sulfuric acid system after longer cycling. Tafel analysis confirmed that the overpotential of hydrogen evolution was lowered for the Pb-Tydrolyte system, which could introduce possible undesirable effects in the lead-acid battery at high charge voltages. The higher hydrogen reaction rate for Tydrolyte is discussed and mitigation strategies are proposed.

Modeling, optimal control of intervention strategies and cost effectiveness analysis for buruli ulcer model

A mathematical model for the transmission of buruli ulcer disease is proposed in this paper, incorporating three control strategies. Using the stability theory of differential equations, optimal control, and computer simulation, a nonlinear mathematical model for the problem is developed and qualitatively analyzed. Buruli ulcer free equilibrium and buruli ulcer present equilibrium were established. Using the next-generation operator method, the basic reproduction number of the model is obtained. It is found that the buruli ulcer-free equilibrium point is asymptotically stable locally and globally when R0<1 and otherwise when R0>1. The bifurcation analysis performed in this study indicates that the buruli ulcer model exhibits backward bifurcation. To investigate the parameters that influence the basic reproduction number R0, sensitivity analysis is performed. To minimize the transmission dynamics of buruli ulcer in humans and water bugs populations respectively, the buruli ulcer model is updated to include control measures attached to the parameters that affect the R0. In particular, the prevention measures covered are health education on the use of protective clothing, treatment of infected humans, and spraying of insecticides. The Pontryagin’s maximum principle is used to characterize the controls’ optimal levels. Using forward and backward sweep techniques in MATLAB, the optimality system was solved numerically. The results of the simulations show that, relative to the case of no control, there is a substantial decrease in the population of infected humans and the total population of water bugs when control measures are implemented. A study of cost-effectiveness shows that the most cost-effective approach is strategy G with the smallest ICER of 33442.44. To mitigate or eliminate buruli ulcer in the population, we conclude that the government should invest in health education on the use of protective clothing, treatment of infected humans, and the use of insecticide spray.

Extraction of Least‐Dispersive Ultrasonic Guided Wave Mode in Rail Track Based on Floquet‐Bloch Theory

Ultrasonic guided wave (UGW) has shown great potential in the field of structural health monitoring of rail tracks due to its long‐range capability and full cross section coverage. However, the practical application of UGW has been hindered by the complicated signal interpretation because of the natures of multiple modes and dispersion. Therefore, it is desirable that the effective UGW modes with high excitability and least dispersion can be identified and extracted for practical applications. In this paper, a numerical study on the guided wave propagation was carried out on a standard rail with 56E1 profile. Firstly, Floquet‐Bloch theory was applied to obtain the dispersion curves of guided wave in a rail. Then, a 3D FE model was built to investigate the UGW propagation along the rail within the frequency range of 0–120 kHz. Wavenumber‐frequency analysis method was applied to decompose and identify the propagating UGW modes. With a carefully designed 2D bandpass filter, a specific mode W0 was extracted in the wavenumber‐frequency domain. Finally, a frequency band sweep technique was also proposed to get the optimal frequency band to achieve a pure and least‐dispersive UGW mode along the rail web. The proposed method provides an effective way to extract efficient UGW modes to assess the integrity of the rail track, as well as other waveguides with complex geometry.

Deciphering the dynamics of lamellipodium in a fish keratocytes model

Motile cells depend on an intricate network of feedback loops that are essential in driving cell movement. Integrin-based focal adhesions (FAs) along with actin are the two key factors that mediate such motile behaviour. Together, they generate excitable dynamics that are essential for forming protrusions at the leading edge of the cell and, in certain cases, traveling waves along the membrane. A partial differential equation (PDE) model of a self-organizing lamellipodium in crawling keratocytes has been previously developed to understand how the three spatiotemporal patterns of activity observed in such cells, namely, stalling, waving and smooth motility, are produced. The model consisted of three key variables: the density of barbed actin filaments, newly formed FAs called nascent adhesions (NAs) and VASP, an anti-capping protein that gets sequestered by NAs during maturation. Using parameter sweeping techniques, the distinct regimes of behaviour associated with the three activity patterns were identified. In this study, we convert the PDE model into an ordinary differential equation (ODE) model to examine its excitability properties and determine all the patterns of activity exhibited by this system. Our results reveal that there are two additional regimes not previously identified, including bistability and oscillatory-like type IV excitability (generated by three steady states and their manifolds, rather than limit cycles). These regimes are also present in the PDE model. Applying slow-fast analysis on the ODE model shows that it exhibits a canard explosion through a folded-saddle and that rough motility seen in keratocytes is likely due to noise-dependent motility governed by dynamics near the interface of bistability and type IV excitability. The two parameter bifurcation suggests that the increase in the proportion of rough motion is due to a shift in activity towards the bistable and type IV excitable regimes induced by a decrease in NA maturation rate. Our results thus provide important insight into how microscopic mechanical effects are integrated to produce the observed modes of motility.

Large depth-of-field three-dimensional shape measurement with the focal sweep technique.

Three-dimensional (3D) shape measurement based on the fringe projection technique has been extensively used for scientific discoveries and industrial practices. Yet, one of the most challenging issues is its limited depth of field (DOF). This paper presents a method to drastically increase DOF of 3D shape measurement technique by employing the focal sweep method. The proposed method employs an electrically tunable lens (ETL) to rapidly sweep the focal plane during image integration and the post deconvolution algorithm to reconstruct focused images for 3D reconstruction. Experimental results demonstrated that our proposed method can achieve high-resolution and high-accuracy 3D shape measurement with greatly improved DOF in real time.

Accurate spherical harmonics solutions for neutron transport problems in multi-region spherical geometry

A stable spherical harmonics (PN) method for solving the problem of a multi-region sphere with internal sources subject to an externally incident angular flux is developed. The method consists in solving the problem locally (region by region) and using an iterative sweep technique to connect and update the solutions for the different regions until global convergence is attained. A post-processing step which is very effective in improving the PN solutions is also developed. Since calculating the current from its definition in terms of the angular flux is prone to loss of precision in spherical geometry, an alternative scheme for computing accurate post-processed currents is devised.Because the developed method does not rely on space and angle discretizations, it can achieve very accurate results even for problems with solutions that display strong flux gradients. This kind of problem is challenging for methods built on discretization schemes. An example of such a problem is solved and the results obtained demonstrate the good performance of the method. Accurate numerical results are also given for two variants of the example problem that involve changes in the driving term and in the scattering law.

Nonmatching Discontinuous Cartesian Grid Algorithm Based on the Multilevel Octree Architecture for Discrete Ordinates Transport Calculation

Obtaining sufficiently accurate geometric descriptions is a crucial prerequisite for reliable particle transport calculations. Conventional transport algorithms on Cartesian grids use a highly efficient sweep technique and numerous mature discretization methods despite their modeling deficiency for complex geometries. To achieve a more accurate geometric description, a cell-based nonmatching Cartesian grid algorithm is proposed on the basis of the multilevel octree architecture. Transport sweep is performed according to the tree branch relationship of nested mesh distributions. The angular flux transmission between discontinuous grids is handled by the flux spatial moment mapping technique, and multiple zero-order mapping schemes are developed, including finite element interpolation, distance interpolation, and exponential fitting methods for treating upwind flux distributions of different relative shapes. The first-order mapping schemes are modified and improved for linear and exponential short characteristic discretization methods. The mapping accuracy is evaluated for polynomial and exponential functions, and a new spatial shape factor is presented for measuring the degree of nonlinearity. The multilevel octree grid (MLTG) algorithm is tested for neutron transport benchmarks, and good agreement with Monte Carlo and standard SN results is achieved. The number of meshes in the VVER shielding model is reduced from 18 million to 2 million using 3-level octree grids with the same geometric description accuracy. Numerical verification of a one-group fixed-source problem shows that 4-level and 5-level MLTG results with proper spatial discretization schemes can achieve relative deviations of less than 3% and 5% for detector region flux, respectively.