Ammar Hakim
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View article: A Conservative Discontinuous Galerkin Algorithm for Particle Kinetics on Smooth Manifolds
A Conservative Discontinuous Galerkin Algorithm for Particle Kinetics on Smooth Manifolds Open
A novel, conservative discontinuous Galerkin algorithm is presented for particle kinetics on manifolds. The motion of particles on the manifold is represented using using both canonical and non-canonical Hamiltonian formulations. Our schem…
View article: Gyrokinetic Simulations of a Low Recycling Scrape-off Layer without a Lithium Target
Gyrokinetic Simulations of a Low Recycling Scrape-off Layer without a Lithium Target Open
Low-recycling regimes are appealing because they entail a high edge temperature and low edge density which are good for core confinement. However, due to considerably enhanced heat flux, the exhaust problems become severe. In addition, in …
View article: Axisymmetric gyrokinetic simulation of ASDEX-Upgrade scrape-off layer using a conservative implicit BGK collision operator
Axisymmetric gyrokinetic simulation of ASDEX-Upgrade scrape-off layer using a conservative implicit BGK collision operator Open
Collisions play an important role in turbulence and transport of fusion plasmas. For kinetic simulations, as the collisionality increases in the domain of interest, the size of the time step to resolve the collisional physics can become ov…
View article: Constructing Field Aligned Coordinate Systems for Gyrokinetic Simulations of Tokamaks in X-point Geometries
Constructing Field Aligned Coordinate Systems for Gyrokinetic Simulations of Tokamaks in X-point Geometries Open
Structures in tokamak plasmas are elongated along the direction of the magnetic field and short in the directions perpendicular to the magnetic field. Many tokamak simulation codes take advantage of this by using a field aligned coordinate…
View article: Towards fully predictive gyrokinetic full-f simulations
Towards fully predictive gyrokinetic full-f simulations Open
Designing economical magnetic confinement fusion power plants motivates computational tools that can estimate plasma behavior from engineering parameters without direct reliance on experimental measurement of the plasma profiles. In this w…
View article: EVALUATION OF SLOPE STABILITY PROBLEMS
EVALUATION OF SLOPE STABILITY PROBLEMS Open
Expansive soils are highly susceptible to volumetric changes due to moisture fluctuations, which can significantly affect the stability and durability of structures. Therefore, their presence must be carefully considered during the plannin…
View article: A parallel-kinetic-perpendicular-moment model for magnetised plasmas
A parallel-kinetic-perpendicular-moment model for magnetised plasmas Open
We describe a new model for the study of weakly collisional, magnetised plasmas derived from exploiting the separation of the dynamics parallel and perpendicular to the magnetic field. This unique system of equations retains the particle d…
View article: A moment-conserving discontinuous Galerkin representation of the relativistic Maxwellian distribution
A moment-conserving discontinuous Galerkin representation of the relativistic Maxwellian distribution Open
Kinetic simulations of relativistic gases and plasmas are critical for understanding diverse astrophysical and terrestrial systems, but the accurate construction of the relativistic Maxwellian, the Maxwell–Jüttner distribution, on a discre…
View article: A kinetic line-driven radiation operator and its application to Gyrokinetics
A kinetic line-driven radiation operator and its application to Gyrokinetics Open
A velocity dependent, kinetic model for line radiation is developed for continuum kinetic codes. It has been implemented in the full- f gyrokinetic code Gkeyll. The total radiation for a charge state is modeled as an advection in velocity …
View article: Direct comparison of gyrokinetic and fluid scrape-off layer simulations
Direct comparison of gyrokinetic and fluid scrape-off layer simulations Open
Typically, fluid simulations are used for tokamak divertor design. However, fluid models are only valid if the scrape-off layer (SOL) is highly collisional. This assumption is valid in many present-day experiments but is questionable in th…
View article: Effects of oxidation and impurities in lithium surfaces on the emitting wall plasma sheath
Effects of oxidation and impurities in lithium surfaces on the emitting wall plasma sheath Open
The use of lithium as a surface coating in fusion devices improves the plasma performance, but the change in the wall properties affects the secondary electron emission properties of the material. Lithium oxidizes easily, which drives the …
View article: Hydrodynamic and Electromagnetic Discrepancies between Neutron Star and Black Hole Spacetimes
Hydrodynamic and Electromagnetic Discrepancies between Neutron Star and Black Hole Spacetimes Open
The exterior spacetime geometry surrounding an uncharged, spinning black hole in general relativity depends only upon its mass and spin. However, the exterior geometry surrounding any other rotating compact object, for example a neutron st…
View article: Improved Dimensionality Reduction for Inverse Problems in Nuclear Fusion and High-Energy Astrophysics
Improved Dimensionality Reduction for Inverse Problems in Nuclear Fusion and High-Energy Astrophysics Open
Many inverse problems in nuclear fusion and high-energy astrophysics research, such as the optimization of tokamak reactor geometries or the inference of black hole parameters from interferometric images, necessitate high-dimensional param…
View article: Direct Comparison of Gyrokinetic and Fluid Scrape-Off Layer Simulations
Direct Comparison of Gyrokinetic and Fluid Scrape-Off Layer Simulations Open
Typically, fluid simulations are used for tokamak divertor design. However, fluid models are only valid if the SOL is highly collisional, an assumption that is valid in many present day experiments but is questionable in the high-power sce…
View article: Effects of oxidation and impurities in lithium surfaces on the emitting wall plasma sheath
Effects of oxidation and impurities in lithium surfaces on the emitting wall plasma sheath Open
Use of lithium as a surface coating in fusion devices improves plasma performance, but the change in wall properties affects the secondary electron emission properties of the material. Lithium oxidizes easily, which drives the emission yie…
View article: Improving Food Packaging Design Considering Performance and Attribute Rating by Using a Novel Fuzzy Framework Based Clustering
Improving Food Packaging Design Considering Performance and Attribute Rating by Using a Novel Fuzzy Framework Based Clustering Open
View article: Reusable Container Usage on a Daily Basis: A Systematic Literature Review
Reusable Container Usage on a Daily Basis: A Systematic Literature Review Open
The issue of plastic waste is a serious social, economic, and cultural issue. Many efforts have been made to reduce the use of disposable food containers and the environmental impact of plastic waste. This study aims to provide an overview…
View article: Decision Analysis on Selecting the Best PSC Scheme between Cost Recovery vs. Gross Split for Block Extension, Case Study: Panca Block
Decision Analysis on Selecting the Best PSC Scheme between Cost Recovery vs. Gross Split for Block Extension, Case Study: Panca Block Open
This research study about the evolution of contract scheme type in Indonesia’s oil and gas industry started in the early 19th century using concession contract agreement change to contract of work and the current well-known existing produc…
View article: A Tetrad-First Approach to Robust Numerical Algorithms in General Relativity
A Tetrad-First Approach to Robust Numerical Algorithms in General Relativity Open
General relativistic Riemann solvers are typically complex, fragile and unwieldy, at least in comparison to their special relativistic counterparts. In this paper, we present a new high-resolution shock-capturing algorithm on curved spacet…
View article: Weak baselines and reporting biases lead to overoptimism in machine learning for fluid-related partial differential equations
Weak baselines and reporting biases lead to overoptimism in machine learning for fluid-related partial differential equations Open
View article: Weak baselines and reporting biases lead to overoptimism in machine learning for fluid-related partial differential equations
Weak baselines and reporting biases lead to overoptimism in machine learning for fluid-related partial differential equations Open
One of the most promising applications of machine learning (ML) in computational physics is to accelerate the solution of partial differential equations (PDEs). The key objective of ML-based PDE solvers is to output a sufficiently accurate…
View article: Conservative discontinuous Galerkin interpolation: Sheared boundary conditions
Conservative discontinuous Galerkin interpolation: Sheared boundary conditions Open
View article: Effect of neutral interactions on parallel transport and blob dynamics in gyrokinetic scrape-off layer simulations
Effect of neutral interactions on parallel transport and blob dynamics in gyrokinetic scrape-off layer simulations Open
The effect of neutral interactions on scrape-off layer (SOL) turbulence is investigated in a continuum gyrokinetic code that has been coupled to a continuum kinetic model of neutral transport. This extends the work of a previous paper [T. …
View article: Toward continuum gyrokinetic study of high-field mirrors
Toward continuum gyrokinetic study of high-field mirrors Open
High-temperature superconducting (HTS) magnetic mirrors under development exploit strong fields with high mirror ratio to compress loss cones and enhance confinement and may offer cheaper, more compact fusion power plant candidates. This n…
View article: Towards continuum gyrokinetic study of high-field mirrors
Towards continuum gyrokinetic study of high-field mirrors Open
High-temperature superconducting (HTS) magnetic mirrors under development exploit strong fields with high mirror ratio to compress loss cones and enhance confinement, and may offer cheaper, more compact fusion power plant candidates. This …
View article: An investigation of shock formation vs shock mitigation of colliding plasma jets
An investigation of shock formation vs shock mitigation of colliding plasma jets Open
This work studies the interaction between colliding plasma jets to understand regimes in which jet merging results in shock formation vs regimes in which the shock formation is mitigated due to the collisionless interpenetration of the jet…
View article: Invariant preservation in machine learned PDE solvers via error correction
Invariant preservation in machine learned PDE solvers via error correction Open
Machine learned partial differential equation (PDE) solvers trade the reliability of standard numerical methods for potential gains in accuracy and/or speed. The only way for a solver to guarantee that it outputs the exact solution is to u…
View article: Dataset from: Towards continuum gyrokinetic study of high-field mirrors
Dataset from: Towards continuum gyrokinetic study of high-field mirrors Open
High-temperature superconducting (HTS) magnetic mirrors under development exploit strong fields with high mirror ratio to compress loss cones and enhance confinement, and may offer cheaper, more compact fusion power plant candidates. This …
View article: Dataset from: Towards continuum gyrokinetic study of high-field mirrors
Dataset from: Towards continuum gyrokinetic study of high-field mirrors Open
High-temperature superconducting (HTS) magnetic mirrors under development exploit strong fields with high mirror ratio to compress loss cones and enhance confinement, and may offer cheaper, more compact fusion power plant candidates. This …
View article: Dataset from: Towards continuum gyrokinetic study of high-field mirrors
Dataset from: Towards continuum gyrokinetic study of high-field mirrors Open
High-temperature superconducting (HTS) magnetic mirrors under development exploit strong fields with high mirror ratio to compress loss cones and enhance confinement, and may offer cheaper, more compact fusion power plant candidates. This …