Edge momentum transport by neutrals: an interpretive numerical framework

Due to their high cross-field mobility, neutrals can contribute to momentum transport even at the low relative densities found inside the separatrix and they can generate intrinsic rotation. We use a charge-exchange dominated solution to the neutral kinetic equation, coupled to neoclassical ions, to evaluate the momentum transport due to neutrals. Numerical solutions to the drift-kinetic equation allow us to cover the full range of collisionality, including the intermediate levels typical of the tokamak edge. In the edge there are several processes likely to contribute to momentum transport in addition to neutrals. Therefore, we present here an interpretive framework that can evaluate the momentum transport through neutrals based on radial plasma profiles. We demonstrate its application by analysing the neutral angular momentum flux for an L-mode discharge in the ASDEX Upgrade tokamak. The magnitudes of the angular momentum fluxes we find here due to neutrals of 0.6 – 2 Nm are comparable to the net torque on the plasma from neutral beam injection, indicating the importance of neutrals for rotation in the edge.Vetenskapsrådet and Marie Sklodowska Curie Actions, Cofund, Project INCA 60039

Repositioning Tiered HotSpot Execution Performance Relative to the Interpreter

Although the advantages of just-in-time compilation over traditional interpretive execution are widely recognised, there needs to be more current research investigating and repositioning the performance differences between these two execution models relative to contemporary workloads. Specifically, there is a need to examine the performance differences between Java Runtime Environment (JRE) Java Virtual Machine (JVM) tiered execution and JRE JVM interpretive execution relative to modern multicore architectures and modern concurrent and parallel benchmark workloads. This article aims to fill this research gap by presenting the results of a study that compares the performance of these two execution models under load from the Renaissance Benchmark Suite. This research is relevant to anyone interested in understanding the performance differences between just-in-time compiled code and interpretive execution. It provides a contemporary assessment of the interpretive JVM core, the entry and starting point for bytecode execution, relative to just-in-time tiered execution. The study considers factors such as the JRE version, the GNU GCC version used in the JRE build toolchain, and the garbage collector algorithm specified at runtime, and their impact on the performance difference envelope between interpretive and tiered execution. Our findings indicate that tiered execution is considerably more efficient than interpretive execution, and the performance gap has increased, ranging from 4 to 37 times more efficient. On average, tiered execution is approximately 15 times more efficient than interpretive execution. Additionally, the performance differences between interpretive and tiered execution are influenced by workload category, with narrower performance differences observed for web-based workloads and more significant differences for Functional and Scala-type workloads.Comment: 17 page

Perspectives on safety culture

Overviewing selected elements from the literature, this paper locates the notion of safety culture within its parent concept of organisational culture. A distinction is drawn between functionalist and interpretive perspectives on organisational culture. The terms ‘culture’ and ‘climate’ are clarified as they are typically applied to organisations and to safety. A contrast is drawn between strategic top down and data-driven bottom up approaches to human factors as an illustrative aspect of safety. A safety case study is used to illustrate two measurement approaches. Key issues for future study include valid measurement of safety culture and developing methods to adequately represent mechanisms through which safety culture might influence, and be influenced by, other safety factors

토카막 통합 시뮬레이션 코드의 개발과 여러 장치에 대한 적용 연구

학위논문(박사) -- 서울대학교대학원 : 공과대학 에너지시스템공학부, 2022. 8. 나용수.The in-depth design and implementation of a newly developed integrated suite of codes, TRIASSIC (tokamak reactor integrated automated suite for simulation and computation), are reported. The suite comprises existing plasma simulation codes, including equilibrium solvers, 1.5D and 2D plasma transport solvers, neoclassical and anomalous transport models, current drive and heating (cooling) models, and 2D grid generators. The components in TRIASSIC could be fully modularized, by adopting a generic data structure as its internal data. Due to a unique interfacing method that does not depend on the generic data itself, legacy codes that are no longer maintained by the original author were easily interfaced. The graphical user interface and the parallel computing of the framework and its components are also addressed. The verification of TRIASSIC in terms of equilibrium, transport, and heating is also shown. Following the data model and definition of the data structure, a declarative programming method was adopted in the core part of the framework. The method was used to keep the internal data consistency of the data by enforcing the reciprocal relations between the data nodes, contributing to extra flexibility and explicitness of the simulations. TRIASSIC was applied on various devices including KSTAR, VEST, and KDEMO, owing to its flexibility in composing a workflow. TRIASSIC was validated against KSTAR plasmas in terms of interpretive and predictive modelings. The prediction and validation on the VEST device using TRIASSIC are also shown. For the applications to the upcoming KDEMO device, the machine design parameters were optimized, targeting an economical fusion demonstration reactor.본 연구에서는 TRIASSIC (tokamak reactor integrated automated suite for simulation and computation) 코드의 자세한 디자인과 실행 결과에 대해 소개합니다. 이 시뮬레이션 코드는 기존에 존재하던 플라즈마 평형, 1.5차원 및 2차원 플라즈마 수송, 신고전 및 난류 수송 모델, 전류 구동 및 가열 (냉각) 모델, 그리고 2차원 격자 생성기 등의 코드를 구성하여 만들어졌습니다. 프레임워크 내 데이터 구조로써 일반 데이터 구조를 채택함으로써 TRIASSIC의 코드 구성요소들은 완전한 모듈화 방식으로 결합될 수 있었습니다. 일반 데이터 구조에 의존하지 않는 독특한 코드 결합 방식으로 인해, 더 이상 유지보수되지 않는 레거시 코드들 또한 쉽게 결합될 수 있었습니다. 본 코드의 그래피컬 유저 인터페이스, 프레임워크와 코드 구성 요소들의 병렬 컴퓨팅에 관한 내용도 다뤄집니다. 평형, 수송, 그리고 가열 측면에서의 TRIASSIC 시뮬레이션의 검증 내용도 소개됩니다. 시뮬레이션 프레임워크 내 일반 데이터 구조의 데이터 모델과 데이터 정의를 만족시키기 위해, 데이터를 관리하는 프레임워크의 중심부에는 선언적 프로그래밍이 도입되었습니다. 선언적 프로그래밍을 통해 일반 데이터의 데이터 노드 간 관계식을 만족시킴으로써 데이터 간 내부 일관성을 확보하고, 코드의 유연성과 명시성을 추가적으로 확보할 수 있었습니다. TRIASSIC은 해석적, 예측적 모델링 측면에서 KSTAR 플라즈마를 대상으로 검증되었습니다. VEST 장치를 대상으로 한 예측 및 이에 대한 검증 내용 또한 서술됩니다. 경제적인 핵융합 실증로 건설을 목표로 KDEMO 장치에 대한 적용 및 장치 설계 최적화 연구도 소개됩니다.Abstract １ Table of Contents ２ List of Figures ４ List of Tables １０ Chapter 1. Introduction １１ 1.1. Background １１ 1.1.1. Fusion Reactor and Modeling １１ 1.1.2. Interpretive Analysis and Predictive Modeling １７ 1.1.3. Modular Approach ２１ 1.1.4. The Standard Data Structure ２４ 1.1.5. The Internal Data Consistency in a Generic Data ２８ 1.1.6. Integration of Physics Codes into IDS ２９ 1.2. Overview of the Research ３１ Chapter 2. Development of Integrated Suite of Codes ３３ 2.1. Development of TRIASSIC ３３ 2.1.1. Design Requirements ３３ 2.1.2. Overview of TRIASSIC ３５ 2.1.3. Comparison of Integrated Simulation Codes ４０ 2.2. Components in the Framework ４３ 2.2.1. Physics Codes Interfaced with the Framework ４３ 2.2.2. Physics Code Interfacings ４６ 2.2.3. Graphical User Interface ５２ 2.2.4. Jobs Scheduler and MPI ５５ 2.3. Verifications ５７ 2.3.1. The Coordinate Conventions ５７ 2.3.2. Coupling of Equilibrium-Transport ５９ 2.3.3. Neoclassical Transport and Bootstrap Current ６３ 2.3.4. Heating and Current Drive ６５ Chapter 3. Improvements in Keeping the Internal Data Consistency ６８ 3.1. Background ６８ 3.2. Possible Implementations of a Component ７１ 3.3. A Method Adopted in the Framework ７３ 3.3.1. Prerequisites and Relation Definitions ７３ 3.3.2. Adding Relations in the Framework ７８ 3.3.3. Applying Relations ８０ 3.4. Performance and Flexibility of the Framework ８３ 3.4.1. Performance Enhancement ８３ 3.4.2. Flexibility and Maintenance of the Framework ８５ Chapter 4. Applications to Various Devices ９１ 4.1. Applications to KSTAR ９１ 4.1.1. Kinetic equilibrium workflow and its validation ９１ 4.1.2. Stationary-state predictive modeling workflow ９５ 4.2. Application to VEST １０２ 4.2.1. Time-dependent predictive modeling workflow １０３ 4.3. Application to KDEMO １０６ 4.3.1. Predictive simulation workflow for optimization １０６ Chapter 5. Summary and Conclusion １１２ 5.1. Summary and Conclusion １１２ Appendix １１６ A. Code Snippet of the Relation Definition １１６ Bibliography １１８ Abstract in Korean １２６박

Functional design for operational earth resources ground data processing

The author has identified the following significant results. Study emphasis was on developing a unified concept for the required ground system, capable of handling data from all viable acquisition platforms and sensor groupings envisaged as supporting operational earth survey programs. The platforms considered include both manned and unmanned spacecraft in near earth orbit, and continued use of low and high altitude aircraft. The sensor systems include both imaging and nonimaging devices, operated both passively and actively, from the ultraviolet to the microwave regions of the electromagnetic spectrum

A programme management approach for ensuring coherence in IS (higher) education

This paper examines IS higher education, concentrating on issues of ‘coherence’ in IS curricula. While curriculum coherence can be jeopardized by poor curriculum design, misalignment between module content and/or misalignment between module or course aims can cause serious coherence issues over time. Misalignment of this type is exacerbated by the traditional processes of curriculum (re)design, which rely heavily on the (singular) interpretation of highly abstract documents, such as module syllabi and course specifications – often produced by curriculum designers in isolation. To improve curriculum coherence, this paper examines the use of a programme management framework as a means of (a) ‘humanizing’ the abstract aims and goals of curricula schemes and (b) managing the delivery and evolution of curricula in relation to the stakeholders in the process of delivery. The practical use of the framework is examined in the context of a Masters-level course in ‘Information Systems Management’. An action research approach is used to demonstrate the practical utility of the framework in terms of (a) improving communication of curricula, (b) improving the coherence between modules and between modules and course and (c) removing content redundancy. Guidelines are presented that generalize the findings in order that key practices may be adopted by others

Research and Education in Computational Science and Engineering

Over the past two decades the field of computational science and engineering (CSE) has penetrated both basic and applied research in academia, industry, and laboratories to advance discovery, optimize systems, support decision-makers, and educate the scientific and engineering workforce. Informed by centuries of theory and experiment, CSE performs computational experiments to answer questions that neither theory nor experiment alone is equipped to answer. CSE provides scientists and engineers of all persuasions with algorithmic inventions and software systems that transcend disciplines and scales. Carried on a wave of digital technology, CSE brings the power of parallelism to bear on troves of data. Mathematics-based advanced computing has become a prevalent means of discovery and innovation in essentially all areas of science, engineering, technology, and society; and the CSE community is at the core of this transformation. However, a combination of disruptive developments---including the architectural complexity of extreme-scale computing, the data revolution that engulfs the planet, and the specialization required to follow the applications to new frontiers---is redefining the scope and reach of the CSE endeavor. This report describes the rapid expansion of CSE and the challenges to sustaining its bold advances. The report also presents strategies and directions for CSE research and education for the next decade.Comment: Major revision, to appear in SIAM Revie