ICRF Heating in JET During Initial Operations with the ITER-like Wall
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Jacquet, P.↗
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A fast non-Fourier method for Landau-fluid operators
An efficient and versatile non-Fourier method for the computation of Landau-fluid (LF) closure operators [Hammett and Perkins, Phys. Rev. Lett. 64, 3019 (1990)] is presented, based on an approximation by a sum of modified-Helmholtz-equation solves (SMHS) in configuration space. This method can yield fast-Fourier-like scaling of the computational time requirements and also provides a very compact data representation of these operators, even for plasmas with large spatial nonuniformity. As a result, the method can give significant savings compared with direct application of “delocalization kernels” [e.g., Schurtz et al., Phys. Plasmas 7, 4238 (2000)], both in terms of computational cost and memory requirements. The method is of interest for the implementation of Landau-fluid models in situations where the spatial nonuniformity, particular geometry, or boundary conditions render a Fourier implementation difficult or impossible. Systematic procedures have been developed to optimize the resulting operators for accuracy and computational cost. The four-moment Landau-fluid model of Hammett and Perkins has been implemented in the BOUT++ code using the SMHS method for LF closure. Excellent agreement has been obtained for the one-dimensional plasma density response function between driven initial-value calculations using this BOUT++ implementation and matrix eigenvalue calculations using both Fourier and SMHS non-Fourier implementations of the LF closures. The SMHS method also forms the basis for the implementation, which has been carried out in the BOUT++ code, of the parallel and toroidal drift-resonance LF closures. The method is a key enabling tool for the extension of gyro-Landau-fluid models [e.g., Beer and Hammett, Phys. Plasmas 3, 4046 (1996)] to codes that treat regions with strong profile variation, such as the tokamak edge and scrapeoff-layer.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Understanding nuclear motions in molecules: Derivation of Eckart frame ro-vibrational Hamiltonian operators via a gateway Hamiltonian operator
A new ro-vibrational Hamiltonian operator, named gateway Hamiltonian operator, with exact kinetic energy term, T-hat, is presented. It is in the Eckart frame and it is of the same form as Watson’s normal coordinate Hamiltonian. However, the vibrational coordinates employed are not normal coordinates. The new Hamiltonian is shown to provide easy access to Eckart frame ro-vibrational Hamiltonians with exact T-hat given in terms of any desired set of vibrational coordinates. A general expression of the Eckart frame ro-vibrational Hamiltonian operator is given and some of its properties are discussed.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Boundary dual of bulk local operators
We provide a procedure to determine if a given nonlocal operator in a large N holographic CFT is dual to a local bulk operator on the geometry associated with a particular code subspace of the CFT. This procedure does not presuppose knowledge of the bulk geometry. We are able to pick out local operators in a large region of the bulk, called the "localizable region,"' that can extend beyond event horizons in certain cases. The method relies heavily on the quantum-error correcting structure of AdS/CFT and, in particular, on entanglement wedge reconstruction. As a byproduct of this machinery, we are able to reconstruct the metric in the localizable region up to a conformal factor. This suggests a connection between our program and the recent light-cone cut approach to bulk reconstruction.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Porting the Kitten Lightweight Kernel Operating System to RISC-V
Hardware design in high-performance computing (HPC) is often highly experimental. Exploring new designs is difficult and time-consuming, requiring lengthy vendor cooperation. RISC-V is an open-source processor ISA that improves the accessibility of chip design, including the ability to do hardware/software co-design using open-source hardware and tools. Co-design allows design decisions to easily flow across the hardware/software boundary and influence future design ideas. However, new hardware designs require corresponding software to drive and test them. Conventional operating systems like Linux are massively complex and modification is time-prohibitive. In this paper, we describe our port of the Kitten lightweight kernel operating system to RISC-V in order to provide an alternative to Linux for conducting co-design research. Kitten's small code base and simple resource management policies are well matched for quickly exploring new hardware ideas that may require radical operating system modifications and restructuring. Our evaluation shows that Kitten on RISC-V is functional and provides similar performance to Linux for single-core benchmarks. This provides a solid foundation for using Kitten in future co-design research involving RISC-V.
Gordon, Nick↗
Sensor-Less Current Sharing Over Wide Operating Range for Extended-Duty-Ratio Boost Converter
Not provided.
Engineering↗
Design, Operation, and Controlled-Island Operation of the U.S. Department of Energy Solar Decathlon 2013 Microgrid
This document reports on the design and operation of a high-capacity and high-penetration-ratio microgrid, which consists of 19 photovoltaic-powered residential houses designed by collegiate teams as part of their participation in the U.S. Department of Energy Solar Decathlon 2013. The microgrid was interconnected with the local utility, and resulting net-power and power-quality events were recorded in high detail (1-minute data sampling or better). Also, a controlled-island operation test was conducted to evaluate the microgrid response to additional events such as increased loads (e.g., from electric vehicles) and bypassing of voltage regulators. This temporary ground-laid microgrid was stable under nominal and island-operation conditions; adverse weather and loads did not lead to power-quality degradation.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Human Performance Analysis Depending on Operator Expertise (Student vs. Operator) and Simulator Complexity (Rancor Microworld vs. Compact Nuclear Simulator)
Human reliability analysis (HRA) evaluates human errors and provides human error probabilities (HEPs) for application in probabilistic safety assessment (PSA), which is a comprehensive safety assessment method for nuclear power plants (NPPs). Generally, HRA methods estimate HEPs based on human reliability data collected from actual historical measurement, simulator experiments, or expert judgement. Most recent HRA data collection studies focus on collecting data via full-scope main control room (MCR) simulators with actual licensed reactor operators. Contrary to this, Idaho National Laboratory (INL) has adopted a different approach, which attempts to collect HRA data based on experiment using simplified simulators and student participants by following the Simplified Human Error Experimental Program (SHEEP). This approach has a couple of advantages compared to full-scope data collection. Representatively, it has relatively low entry point for collecting HRA data, and secures large sample sizes with reasonable cost and labor. In the previous studies, we developed the SHEEP framework, then verified whether the data collected through the framework could support a representative full-scope data collection study, i.e., the Human Reliability Data Extraction (HuREX) study. Also, we analyzed human performance measurements depending on participant type (i.e., student vs. operator). In this paper, we analyze human performance data collected from an experiment comparing operator expertise and simulator complexity when using the more simplified simulator developed by INL, i.e., Rancor Microworld and the less simplified simulator, i.e., Compact Nuclear Simulator (CNS) developed by Korea Atomic Energy Research Institute (KAERI). Analysis of variance (ANOVA) tests and correlation analysis are used for analyzing the experimental data.
99 GENERAL AND MISCELLANEOUS↗
Influence of Operating Conditions on Ethanol Passive Prechamber Cold-start Operation
Cold-start operation in spark ignition engines is characterized by many drawbacks such as poor fuel vaporization, substantial wall film formation, and weak ignition which can result in unstable combustion and high concentrations of carbon monoxide (CO), nitrogen oxides (NOx), and unburnt hydrocarbons (UHC) prior to catalyst light-off. These challenges are particularly important for ethanol as the fuel’s high latent heat of vaporization and low vapor pressure can hinder reliable ignition during cold-start. In this context, passive prechamber ignition systems offer a viable pathway to improve ignitability by producing hot turbulent jets that can promote combustion in the main chamber. In this study, the influence of operating conditions on jet formation and combustion characteristics in an ethanol-fueled passive prechamber spark ignition engine is investigated. Two intake pressures (40 kPa and 60 kPa) and two engine speeds (450 and 600 rpm) are studied to represent various stages of the cold-start ramp-up. Results indicate that lower intake pressures lead to delayed and asymmetric turbulent jet formation, and lower peak heat release rates. Lower engine speeds, on the other hand, produced higher peak heat release and faster combustion due to greater residence time in the engine. This greater residence time also increases the likelihood of autoignition in the main chamber, potentially promoting quicker heat release for lower engine speeds. These results provide insight into the role of operating conditions on cold-start ramp-up of passive prechamber engines.
Banagiri, Shrikar [ORNL] (ORCID:0000000239745099)↗
Experimental verification of an energy consumption signal tool for operational decision support in an office building
Not Available
Pavlak, Gregory S. (ORCID:0000000347340750)↗
Top-gate organic field-effect transistors fabricated on paper with high operational stability
Not provided.
Materials Science↗
Ion Exchange Gels Allow Organic Electrochemical Transistor Operation with Hydrophobic Polymers in Aqueous Solution
Conjugated-polymer-based organic electrochemical transistors (OECTs) are being studied for applications ranging from biochemical sensing to neural interfaces. While new polymers that interface digital electronics with the aqueous chemistry of life are being developed, the majority of high-performance organic transistor materials are poor at transporting biologically relevant ions. Here, the operating mode of an organic transistor is changed from that of an electrolyte-gated organic field-effect transistor (EGOFET) to that of an OECT by incorporating an ion exchange gel between the active layer and the aqueous electrolyte. This device works by taking up biologically relevant ions from solution and injecting more hydrophobic ions into the active layer. Using poly[2,5-bis(3-tetradecylthiophen-2-yl) thieno[3,2-b]thiophene] as the active layer and a blend of an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and poly(vinylidene fluoride-co-hexafluoropropylene) as the ion exchange gel, four orders of magnitude improvement in device transconductance and a 100-fold increase in kinetics are demonstrated. The ability of the ion-exchange-gel OECT to record biological signals by measuring the action potentials of a Venus flytrap is demonstrated. These results show the possibility of using interface engineering to open up a wider palette of organic semiconductors as OECTs that can be gated by aqueous solutions.
Bischak, Connor G.↗
High Voltage Operation of Ni-Rich NMC Cathodes Enabled by Stable Electrode/Electrolyte Interphases
Lithium (Li) metal battery (LMB) is one of the most promising candidates for the next generation energy storage systems. However, it is still a significant challenge to operate LMBs with high voltage cathode under high rate conditions. In this work, a LMB using nickel-rich layered cathode of LiNi0.76Mn0.14Co0.10O2 (NMC76) and an optimized electrolyte (0.6 M LiTFSI + 0.4 M LiBOB + 0.05 M LiPF6 dissolved in EC: EMC (4:6 by weight)) demonstrate excellent stability under a high charge cutoff voltage of 4.5 V. Remarkably, these Li||NMC76 cells can deliver a high discharge capacity of > 220 mAh g-1 (846 Wh kg-1) and retain more than 80% capacity after 1000 cycles under a high charge/discharge current rates of 2C/2C (1C = 200 mA g-1). These excellent electrochemical performances can be attributed to the highly enhanced structural/interfacial stability of both Ni-rich NMC76 cathode materials and Li metal anode using the optimized electrolyte.
Ni-rich NMC, cathode electrolyte interphase, dual ↗
Operable adaptive sparse identification of systems: Application to chemical processes
Not provided.
Engineering↗
The unexpected virtue of almost: Exploiting MPI collective operations to approximately coordinate checkpoints
Summary Coordinated checkpoint/restart is currently the dominant approach to mitigating the impact of failures on important scientific applications running on large‐scale distributed systems. However, there is widespread evidence that coordinated checkpointing may no longer be viable on next‐generation systems. Uncoordinated checkpoint/restart attempts to address the shortcomings of coordinated checkpoint/restart by allowing application processes to checkpoint their state independently. However, eliminating coordination may significantly degrade application performance. In this paper, we propose an approach that leverages existing coordination in important scientific applications to approximately coordinate checkpoints. Specifically, we propose to extend MPI implementations to force checkpoints to occur immediately after the completion of a collective operation. We evaluate the performance implications of this approach using an existing validated simulation framework. Our results demonstrate that approximately coordinated checkpointing can significantly improve application performance relative to totally uncoordinated checkpointing. We also show that forcing checkpoints to occur following a collective operation has a small impact on the nominal checkpoint interval for several important workloads. As a whole, the results presented in this paper demonstrate that approximately coordinated checkpointing may provide significant performance benefits without significantly increasing the cost of failure recovery.
Levy, Scott↗