509 research outputs found
‘Whether you go illegally or legally in the end it’s the same, you’re cheated’: A study of formal and informal recruitment practices of Lao workers migrating to Thailand
Non-linear Simulations of MHD Instabilities in Tokamaks Including Eddy Current Effects and Perspectives for the Extension to Halo Currents
The dynamics of large scale plasma instabilities can strongly be influenced
by the mutual interaction with currents flowing in conducting vessel
structures. Especially eddy currents caused by time-varying magnetic
perturbations and halo currents flowing directly from the plasma into the walls
are important. The relevance of a resistive wall model is directly evident for
Resistive Wall Modes (RWMs) or Vertical Displacement Events (VDEs). However,
also the linear and non-linear properties of most other large-scale
instabilities may be influenced significantly by the interaction with currents
in conducting structures near the plasma. The understanding of halo currents
arising during disruptions and VDEs, which are a serious concern for ITER as
they may lead to strong asymmetric forces on vessel structures, could also
benefit strongly from these non-linear modeling capabilities. Modeling the
plasma dynamics and its interaction with wall currents requires solving the
magneto-hydrodynamic (MHD) equations in realistic toroidal X-point geometry
consistently coupled with a model for the vacuum region and the resistive
conducting structures. With this in mind, the non-linear finite element MHD
code JOREK has been coupled with the resistive wall code STARWALL, which allows
to include the effects of eddy currents in 3D conducting structures in
non-linear MHD simulations. This article summarizes the capabilities of the
coupled JOREK-STARWALL system and presents benchmark results as well as first
applications to non-linear simulations of RWMs, VDEs, disruptions triggered by
massive gas injection, and Quiescent H-Mode. As an outlook, the perspectives
for extending the model to halo currents are described.Comment: Proceeding paper for Theory of Fusion Plasmas (Joint Varenna-Lausanne
International Workshop), Varenna, Italy (September 1-5, 2014); accepted for
publication in: to Journal of Physics: Conference Serie
Comparing spontaneous and pellet-triggered ELMs via non-linear extended MHD simulations
Injecting frozen deuterium pellets into an ELMy H-mode plasma is a well established scheme for triggering edge localized modes (ELMs) before they naturally occur. This paper presents non-linear simulations of spontaneous type-I ELMs and pellet-triggered ELMs in ASDEX Upgrade performed with the extended MHD code JOREK. A thorough comparison of the non-linear dynamics of these events is provided. In particular, pellet-triggered ELMs are simulated by injecting deuterium pellets into different time points during the pedestal build-up described in A Cathey et al (2020 Nuclear Fusion 60 124007). Realistic ExB and diamagnetic background plasma flows as well as the time dependent bootstrap current evolution are included during the build-up to accurately capture the balance between stabilising and destabilising terms for the edge instabilities. Dependencies on the pellet size and injection times are studied. The spatio-temporal structures of the modes and the resulting divertor heat fluxes are compared in detail between spontaneous and triggered ELMs. We observe that the premature excitation of ELMs by means of pellet injection is caused by a helical perturbation described by a toroidal mode number of n=1. In accordance with experimental observations, the pellet-triggered ELMs show reduced thermal energy losses and a narrower divertor wetted area with respect to spontaneous ELMs. The peak divertor energy fluence is seen to decrease when ELMs are triggered by pellets injected earlier during the pedestal build-up.</p
PAS Update aanvullende reservemaatregelen Landbouw
In many Natura 2000 area’s, the nitrogen deposition is higher than wished for. This led to a deadlock in economic development of,among others,livestock husbandry. For the three sector groups Traffic and Transportation, Industry and Energy, and Agriculture source measures were listedin 2017 to deal with the bottlenecks. For agriculture, the list with measures is updated in consultation with representatives of the agricultural sector, research and policy, developed and written in this present report. This study was performed by order of the Ministry of Agriculture, Nature and Food qualitybefore the Council of State made judgement regarding PAS
Theorising age and generation in development: A relational approach
This introduction outlines the analytical approach informing the articles presented in this special issue. The project of ‘generationing’ development involves re-thinking development as distinctly generational in its dynamics. For this, we adopt a relational approach to the study of young people in development, which overcomes the limitations inherent to common categorising approaches. Concepts of age and generation are employed to conceptualise young people as social actors and life phases such as childhood and youth in relational terms. Acknowledging the centrality of young people in social reproduction puts them at the heart of development studies and leads the articles comprising this special issue to explore how young people’s agency shapes and is shaped by the changing terms of social reproduction brought about by development
Nitrogen and sulphur management: challenges for organic sources in temperate agricultural systems
A current global trend towards intensification or specialization of agricultural enterprises has been accompanied by increasing public awareness of associated environmental consequences. Air and water pollution from losses of nutrients, such as nitrogen (N) and sulphur (S), are a major concern. Governments have initiated extensive regulatory frameworks, including various land use policies, in an attempt to control or reduce the losses. This paper presents an overview of critical input and loss processes affecting N and S for temperate climates, and provides some background to the discussion in subsequent papers evaluating specific farming systems. Management effects on potential gaseous and leaching losses, the lack of synchrony between supply of nutrients and plant demand, and options for optimizing the efficiency of N and S use are reviewed. Integration of inorganic and organic fertilizer inputs and the equitable re-distribution of nutrients from manure are discussed. The paper concludes by highlighting a need for innovative research that is also targeted to practical approaches for reducing N and S losses, and improving the overall synchrony between supply and demand
Case Report: Humeral avulsion of the glenohumeral ligament of the shoulder
A 24-year-old rugby player presented to an orthopaedic surgeon with a history of dislocation of the left shoulder. It reduced spontaneously and dislocated again later during the same match.
On examination there was no residual instability, but the apprehension test for anterior instability was positive. Speed s test as well as O Brien s test for SLAP (Superior Labrum Anterior to Posterior tear) lesions were negative. There were no signs of rotator cuff tear or impingement.
South African Sports Medicine Vol.17(1) 2005: 27-2
Probing non-linear MHD stability of the EDA H-mode in ASDEX Upgrade
Regimes of operation in tokamaks that are devoid of large ELMs have to be
better understood to extrapolate their applicability to reactor-relevant
devices. This paper describes non-linear extended MHD simulations that use an
experimental equilibrium from an EDA H-mode in ASDEX Upgrade. Linear ideal MHD
analysis indicates that the operational point lies slightly inside of the
stable region. The non-linear simulations with the visco-resistive extended MHD
code, JOREK, sustain non-axisymmetric perturbations that are linearly most
unstable with toroidal mode numbers of n = \{6 \dots 9\}, but non-linearly
higher and lower n become driven and the low-n become dominant. The poloidal
mode velocity during the linear phase is found to correspond to the expected
velocity for resistive ballooning modes. The perturbations that exist in the
simulations have somewhat smaller poloidal wavenumbers (k_{\theta} \sim 0.1 to
0.5 cm^{-1} ) than the experimental expectations for the quasi-coherent mode in
EDA, and cause non-negligible transport in both the heat and particle channels.
In the transition from linear to non-linear phase, the mode frequency chirps
down from approximately 35 kHz to 13 kHz, which corresponds approximately to
the lower end of frequencies that are typically observed in EDA H-modes in
ASDEX Upgrade
- …