Controllers for high-performance nuclear fusion plasmas

A succesful nuclear fusion reactor will confine plasma at hig temperatures and densities, with low thermal losses. The workhorse of the nuclear fusion community is the tokamak, a toroidal device in which plasmas are confined by poloidal and toroidal magnetic fields. Ideally, the confirming magnetic fields form a set of nested tori. A repetive magnetohydrodynamic (MHD) event in the plasma core (the sawteeth instability) perturbs the confirming magnetic field by producing seed islands. In low-pressure plasmas the seed islands will self-heal. In high-pressure plasmas the seed islands can grow and saturate. These neoclassical tearing models (NTMs) reduce the plasma performance or lead to plasma disruption. This sets the resistive pressure limit in tokamaks. High-performance operation in tokamaks therefore implies the control or amelioration of the NTMs. Controllers for the sawteeth and the NTMs will be discussed, with special emphasis on the development of dedicated sensors and models for MHD control

Electron transport barriers in tokamak plasmas

+139hlm.;23c

The construction of knowledge-based economies versus knowledge societies: The cases of Germany and Singapore

In the past decades, terms such as knowledge-based economy (KBE)\u27, and \u27information/knowledge society\u27 have been adopted by governments worldwide in order to underline their interest in developing their economies and societies further and assure future growth. Many governments used these catchwords as labels for government programs and action plans aiming at economic and social prosperity. This aim of national governments to construct knowledge-based economies, information/knowledge societies, the actions taken and especially the ability or disability to do so, is the topic of this paper. As two cases of comparison act Singapore and Germany. (DIPF/Orig.

Experimental stabilisation of 2D vortex patterns using time-dependent forcing

Experimental results of the effect of time-periodic and "chirped" (electro-magnetic) forcing on vortex patterns in shallow-water-layer flows are presented. Analogously to vibrational control, the use of a time-periodic forcing results in stabilisation of otherwise unstable vortex patterns. Chirped frequency forcing yields self-organising patterns that are different from those in stationary and periodically forced experiments. The results are shown to be consistent with theoretical analysis of 2D Taylor-Green vortices, i.e. unstable analytical solutions of the 2D Navier-Stokes equation. These results imply that, compared to the more often analysed stationary forced flows, time-varying forcing can stabilise different vortex patterns in shallow-water-layer flows

Sawtooth period pacing and locking by EC power control on TCV

Abstract #TP9.127 submitted for the DPP11 Meeting of The American Physical Society

Haptic Shared Control in Tele-Manipulation: Effects of Inaccuracies in Guidance on Task Execution

Haptic shared control is a promising approach to improve tele-manipulated task execution, by making safe and effective control actions tangible through guidance forces. In current research, these guidance forces are most often generated based on pre-generated, errorless models of the remote environment. Hence such guidance forces are exempt from the inaccuracies that can be expected in practical implementations. The goal of this research is to quantify the extent to which task execution is degraded by inaccuracies in the model on which haptic guidance forces are based. In a human-in-the-loop experiment, subjects (n = 14) performed a realistic tele-manipulated assembly task in a virtual environment. Operators were provided with various levels of haptic guidance, namely no haptic guidance (conventional tele-manipulation), haptic guidance without inaccuracies, and haptic guidance with translational inaccuracies (one large inaccuracy, in the order of magnitude of the task, and a second smaller inaccuracy). The quality of natural haptic feedback (i.e., haptic transparency) was varied between high and low to identify the operator\u27s ability to detect and cope with inaccuracies in haptic guidance. The results indicate that haptic guidance is beneficial for task execution when no inaccuracies are present in the guidance. When inaccuracies are present, this may degrade task execution, depending on the magnitude and the direction of the inaccuracy. The effect of inaccuracies on overall task performance is dominated by effects found for the Constrained Translational Movement, due to its potential for jamming. No evidence was found that a higher quality of haptic transparency helps operators to detect and cope with inaccuracies in the haptic guidance.</p

Child Posttraumatic Stress after Parental Cancer: Associations with Individual and Family Factors

Objective This study aimed to examine the severity of posttraumatic stress disorder (PTSD) symptoms in children of parents with cancer and to identify individual and family factors associated with these symptoms. Methods The sample consisted of 175 children (52% girls, aged M ¼ 11.98, SD ¼ 3.20, range ¼ 6–20 years) from 92 families, of which 90 parents with a current or past cancer diagnosis and 71 healthy co-parents also completed questionnaires. Children reported on PTSD symptoms, trauma-related cognitions, emotion regulation difficulties, general family functioning, and family communication. Both parents reported on their own PTSD symptoms. Associations were investigated using multilevel regression. Results Twenty-seven percentage of the children showed clinically relevant PTSD symptoms. Intraclass correlations indicated that children from the same family showed little overlap in these symptoms. Multilevel analyses showed that child trauma-related cognitions and emotion regulation difficulties were related to higher levels of PTSD symptoms at the individual level. General family functioning was only related to child PTSD symptoms at the family level. Child PTSD severity was unrelated to parental PTSD symptoms and family communication at the family level when taking into account the other factors. Conclusions The current study highlights the psychological impact of parental cancer on children. Individual factors contributed more strongly to child PTSD symptoms than family factors. Trauma-related cognitions and emotion regulation difficulties might be targeted through specific psychoeducation for children and parents, family-oriented support and interventions, and evidence-based treatments for child PTSD

Child Posttraumatic Stress after Parental Cancer: Associations with Individual and Family Factors

Objective This study aimed to examine the severity of posttraumatic stress disorder (PTSD) symptoms in children of parents with cancer and to identify individual and family factors associated with these symptoms. Methods The sample consisted of 175 children (52% girls, aged M ¼ 11.98, SD ¼ 3.20, range ¼ 6–20 years) from 92 families, of which 90 parents with a current or past cancer diagnosis and 71 healthy co-parents also completed questionnaires. Children reported on PTSD symptoms, trauma-related cognitions, emotion regulation difficulties, general family functioning, and family communication. Both parents reported on their own PTSD symptoms. Associations were investigated using multilevel regression. Results Twenty-seven percentage of the children showed clinically relevant PTSD symptoms. Intraclass correlations indicated that children from the same family showed little overlap in these symptoms. Multilevel analyses showed that child trauma-related cognitions and emotion regulation difficulties were related to higher levels of PTSD symptoms at the individual level. General family functioning was only related to child PTSD symptoms at the family level. Child PTSD severity was unrelated to parental PTSD symptoms and family communication at the family level when taking into account the other factors. Conclusions The current study highlights the psychological impact of parental cancer on children. Individual factors contributed more strongly to child PTSD symptoms than family factors. Trauma-related cognitions and emotion regulation difficulties might be targeted through specific psychoeducation for children and parents, family-oriented support and interventions, and evidence-based treatments for child PTSD

Strong Scattering of High Power Millimeter Waves in Tokamak Plasmas with Tearing Modes

In tokamak plasmas with a tearing mode, strong scattering of high power millimeter waves, as used for heating and noninductive current drive, is shown to occur. This new wave scattering phenomenon is shown to be related to the passage of the O point of a magnetic island through the high power heating beam. The density determines the detailed phasing of the scattered radiation relative to the O-point passage. The scattering power depends strongly nonlinearly on the heating beam power