721 research outputs found
Toroidal modelling of plasma response and RMP field penetration
The penetration dynamics of the resonant magnetic perturbation (RMP) field is sim-
ulated in the full toroidal geometry, under realistic plasma conditions in MAST experiments.
The physics associated with several aspects of the RMP penetration - the plasma response
and rotational screening, the resonant and non-resonant torques and the toroidal momentum
balance - are highlighted. In particular, the plasma response is found to significantly amplify
the non-resonant component of the RMP field for some of the MAST plasmas. A fast rotating
plasma, in response to static external magnetic fields, experiences a more distributed electro-
magnetic torque due to the resonance with continuum waves in the plasma. At fast plasma
flow (such as for the MAST plasma), the electromagnetic torque is normally dominant over
the neoclassical toroidal viscous (NTV) torque. However, at sufficiently slow plasma flow,
the NTV torque can play a significant role in the toroidal momentum balance, thanks to the
precession drift resonance enhanced, so called superbanana plateau regime
Self-consistent simulation of plasma scenarios for ITER using a combination of 1.5D transport codes and free-boundary equilibrium codes
Self-consistent transport simulation of ITER scenarios is a very important
tool for the exploration of the operational space and for scenario
optimisation. It also provides an assessment of the compatibility of developed
scenarios (which include fast transient events) with machine constraints, in
particular with the poloidal field (PF) coil system, heating and current drive
(H&CD), fuelling and particle and energy exhaust systems. This paper discusses
results of predictive modelling of all reference ITER scenarios and variants
using two suite of linked transport and equilibrium codes. The first suite
consisting of the 1.5D core/2D SOL code JINTRAC [1] and the free boundary
equilibrium evolution code CREATE-NL [2,3], was mainly used to simulate the
inductive D-T reference Scenario-2 with fusion gain Q=10 and its variants in H,
D and He (including ITER scenarios with reduced current and toroidal field).
The second suite of codes was used mainly for the modelling of hybrid and
steady state ITER scenarios. It combines the 1.5D core transport code CRONOS
[4] and the free boundary equilibrium evolution code DINA-CH [5].Comment: 23 pages, 18 figure
IGFBP3 mRNA expression in benign and malignant breast tumors
INTRODUCTION: Most previous studies have focused on evaluating the association between circulating insulin-like growth factor binding protein 3 (IGFBP-3) levels and breast cancer risk. Emerging evidence over the past few years suggests that IGFBP-3 may act directly on mammary epithelial cells. METHODS: To understand the role of IGFBP-3 in breast tumorigenesis, we investigated IGFBP3 mRNA expression levels in benign and malignant breast tumors and their adjacent normal tissues using real-time quantitative PCR. RESULTS: Cancer tissues had significantly lower IGFBP3 expression than benign tumor tissues (p < 0.001). IGFBP3 expressions in both tumor and adjacent tissues were higher in patients who had proliferative benign tumors than in those who had non-proliferative benign tumors. Among patients with benign breast disease, IGFBP3 expression in the tumor was significantly higher than that in their adjacent normal tissue. There were no apparent associations of IGFBP3 expression in cancer tissues with either overall survival or disease-free survival in a cohort of 521 patients with breast cancer. CONCLUSION: Our findings suggest that the expression level of IGFBP3 in breast tissues may be involved in breast tumorigenesis
Towards a strategic understanding of global teams and their HR implications : an expert dialogue
Drawing on initial insights emerging from a panel at the EIBA 2016 Conference in Vienna, here discussants and expert panelists engage in a follow-on conversation on the HRM implications of global teams for international organizations. First we set out how HRM can enable global teams and their constituent members to overcome the new and considerable challenges of global teams. These challenges span levels of analysis, time and space. Next we debate global teams as a strategic response to the dual pressures of global integration and local adaptation. We consider what HRM is needed for global teams to successfully resolve this dilemma, challenging practitioners to move beyond the ‘best practices’ and ‘alignment’ dichotomy. Lastly we look to the future to consider implications for research. We propose a rich research agenda focused on the complexities of the global team context
Aerodynamic investigations of ventilated brake discs.
The heat dissipation and performance of a ventilated brake disc strongly depends
on the aerodynamic characteristics of the flow through the rotor passages. The
aim of this investigation was to provide an improved understanding of ventilated
brake rotor flow phenomena, with a view to improving heat dissipation, as well
as providing a measurement data set for validation of computational fluid
dynamics methods. The flow fields at the exit of four different brake rotor
geometries, rotated in free air, were measured using a five-hole pressure probe
and a hot-wire anemometry system. The principal measurements were taken using
two-component hot-wire techniques and were used to determine mean and unsteady
flow characteristics at the exit of the brake rotors. Using phase-locked data
processing, it was possible to reveal the spatial and temporal flow variation
within individual rotor passages. The effects of disc geometry and rotational
speed on the mean flow, passage turbulence intensity, and mass flow were
determined. The rotor exit jet and wake flow were clearly observed as
characterized by the passage geometry as well as definite regions of high and
low turbulence. The aerodynamic flow characteristics were found to be reasonably
independent of rotational speed but highly dependent upon rotor geometry
Operating a full tungsten actively cooled tokamak: overview of WEST first phase of operation
WEST is an MA class superconducting, actively cooled, full tungsten (W) tokamak, designed to operate in long pulses up to 1000 s. In support of ITER operation and DEMO conceptual activities, key missions of WEST are: (i) qualification of high heat flux plasma-facing components in integrating both technological and physics aspects in relevant heat and particle exhaust conditions, particularly for the tungsten monoblocks foreseen in ITER divertor; (ii) integrated steady-state operation at high confinement, with a focus on power exhaust issues. During the phase 1 of operation (2017–2020), a set of actively cooled ITER-grade plasma facing unit prototypes was integrated into the inertially cooled W coated startup lower divertor. Up to 8.8 MW of RF power has been coupled to the plasma and divertor heat flux of up to 6 MW m−2 were reached. Long pulse operation was started, using the upper actively cooled divertor, with a discharge of about 1 min achieved. This paper gives an overview of the results achieved in phase 1. Perspectives for phase 2, operating with the full capability of the device with the complete ITER-grade actively cooled lower divertor, are also described
Overview of the FTU results
Since the 2018 IAEA FEC Conference, FTU operations have been devoted to several experiments covering a large range of topics, from the investigation of the behaviour of a liquid tin limiter to the runaway electrons mitigation and control and to the stabilization of tearing modes by electron cyclotron heating and by pellet injection. Other experiments have involved the spectroscopy of heavy metal ions, the electron density peaking in helium doped plasmas, the electron cyclotron assisted start-up and the electron temperature measurements in high temperature plasmas. The effectiveness of the laser induced breakdown spectroscopy system has been demonstrated and the new capabilities of the runaway electron imaging spectrometry system for in-flight runaways studies have been explored. Finally, a high resolution saddle coil array for MHD analysis and UV and SXR diamond detectors have been successfully tested on different plasma scenarios
On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection
A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)
Modelling of the effect of ELMs on fuel retention at the bulk W divertor of JET
Effect of ELMs on fuel retention at the bulk W target of JET ITER-Like Wall was studied with multi-scale calculations. Plasma input parameters were taken from ELMy H-mode plasma experiment. The energetic intra-ELM fuel particles get implanted and create near-surface defects up to depths of few tens of nm, which act as the main fuel trapping sites during ELMs. Clustering of implantation-induced vacancies were found to take place. The incoming flux of inter-ELM plasma particles increases the different filling levels of trapped fuel in defects. The temperature increase of the W target during the pulse increases the fuel detrapping rate. The inter-ELM fuel particle flux refills the partially emptied trapping sites and fills new sites. This leads to a competing effect on the retention and release rates of the implanted particles. At high temperatures the main retention appeared in larger vacancy clusters due to increased clustering rate
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