118,516 research outputs found
Traité pratique du gréement des vaisseaux et autres batimens de mer ...
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Evaluation of the REP project: the Rossie-Elms mental health and well-being project
No full textIntroduction: The Rossie/Elms Project (REP) is a specialist mental health project providing services to young people looked after in Rossie Secure Accommodation Services and the Elms Secure Unit. In February 2003 a partnership proposal was submitted by Dundee City Council and Rossie Secure Accommodation Services to obtain funding from the Intensive Support Fund. The funding was to be used to obtain specialist mental health services from Tayside Primary Care NHS Trust. The proposal was submitted on the basis that looked after young people are more likely to experience mental health problems than the general population of young people and to encounter a greater number of 'systematic and personal barriers' to accessing appropriate services (Kendrick, Milligan and Furnivall 2004, Meltzer et al 2003, Richardson and Lelliot 2003, Ridley 2001). The proposal addressed recommendations by the Social Work Services Inspectorate Report (1996) to explore opportunities for fast tracking access to psychiatric and psychological services for young people in secure care. The key elements of the mental health service were: • To promote good mental health and wellbeing • To identify and provide needed therapeutic interventions for young people in secure care • To provide specialist advice and consultancy to staff in order to improve assessment, care planning and the delivery of secure care In May 2003 REP was awarded funding for three years to offer a mental health service within Rossie Secure Accommodation and the Elms Secure Unit. Rossie Secure Accommodation service is located five miles south of Montrose and has places for 28 young people across four units. The Elms Secure Unit, located in Dundee City, is a custom built unit attached to a close support unit. It is licensed for 4 young people staying for a maximum of three months. The first project workers were appointed in September 2003. This included one full time Psychiatric Nurse and a part-time Consultant Psychiatrist. In April 2004, one project worker left the project owing to a promotion. Subsequently two full-time project workers were appointed and in October 2004, a part time secretary was hired. At the time of this report funding enables two full-time Mental Health Workers, a part time Consultant Psychiatrist and one part-time post for secretarial support to be employed across the two units. The project has now been in operation for 2.5 years
Long-lived coupled peeling ballooning modes preceding ELMs on JET
No full textPaperLong-lived coupled peeling ballooning modes preceding ELMs on JETC. Perez von Thun1,2, L. Frassinetti3, L. Horvath4, S. Saarelma5, L. Meneses6, E. de la Luna7, M. Beurskens8, J. Boom9, J. Flanagan5, J.C. Hillesheim5Show full author listPublished 22 March 2019 • © EURATOM 2019Nuclear Fusion, Volume 59, Number 5Download Article PDFFiguresReferencesDownload PDF80 Total downloadsTurn on MathJaxGet permission to re-use this articleShare this article Share this content via email Share on Facebook Share on Twitter Share on Google+ Share on CiteULike Share on MendeleyArticle informationAbstractIn some JET discharges, type-I edge localised modes (ELMs) are preceded by a class of low-frequency oscillations (Perez et al 2004 Nucl. Fusion 44 609). While in many cases the ELM is triggered during the growth phase of this oscillation, it is also observed that this type of oscillation can saturate and last for several tens of ms until an ELM occurs. In order to identify the nature of these modes, a wide pre-ELM oscillation database, including detailed pedestal profile information, has been assembled and analysed in terms of MHD stability parameters. The existence domain of these pre-ELM oscillations and the statistical distribution of toroidal mode numbers (n) up to n = 16 have been mapped in ballooning alpha () and either edge current density () or pedestal collisionality () coordinates and compared to linear MHD stability predictions. The pre-ELM oscillations are reliably observed when the ratio is high enough for the pedestal to access the coupled peeling-ballooning (PB) domain (aka stability nose). Conversely, when the pedestal is found to be in or near the high-n ballooning domain (which is at low ratio), ELMs are usually triggered promptly, i.e. with no detectable pre-ELM oscillations, or with pre-ELM oscillations only observable on ECE whose n appears to be too high to be resolved by the magnetics. Individual discharges can sometimes exhibit a fairly wide range of pre-ELM mode numbers, but for a wider database, the statistical n-number domains are found to be well ordered along the stability boundary and behave as expected from PB theory: the higher the ratio, the lower the mode's measured n tends to be. Within the measurement uncertainties, the measured n is usually found to be compatible with the most unstable n predicted by the linear stability code MISHKA1. These results confirm the earlier hypothesis that these modes are coupled peeling-ballooning modes, and extend and generalise to higher-mode numbers the work by Huysmans et al (1998 Nucl. Fusion 38 179), who identified the lowest n modes as pure external kink modes. Since the destabilisation of PB modes is widely accepted to give rise to ELMs, the mode saturation and delayed ELM triggering that is sometimes observed is rather unexpected. Possibilities to reconcile the extended lifetime of these modes with current ELM models are briefly discussed, but will require further investigation
tfelm: a TensorFlow Toolbox for the Investigation of ELMs and MLPs Performance
No full textExtreme learning machine (ELMs) and gradient-based multilayer perceptrons (MLPs) have competing performance, in terms of learning speed and model accuracy. Thus, with reference to a specific application, it is of interest to establish whether the performance of ELMs are better than those achieved with MLPs. To this end this paper proposes a unified framework for the investigation of ELMs and MLPs performance in real data sets. The tool is based on Google’s TensorFlow architecture and is able to overcome the lack of previously available ELMs libraries. A wide experimentation on both toy and benchmark datasets shows the usefulness of the tool
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A review of ELMs in divertor tokamaks
No full textThis paper reviews what is known about edge localized modes (ELMs), with an emphasis on their effect on the scrape-off layer and divertor plasmas. ELM effects have been measured in the ASDEX-U, C-Mod, COMPASS-D, DIII-D, JET, JFT-2M,JT-60U, and TCV tokamaks and are reported here. At least three types of ELMs have been identified and their salient features determined. Type-1 giant ELMs can cause the sudden loss of up to 10-15% of the plasma stored energy but their amplitude ({Delta}W/W) does not increase with increasing power. Type- 3 ELMs are observed near the H-mode power threshold and produce small energy dumps (1-3% of the stored energy). All ELMs increase the scrape- off layer plasma and produce particle fluxes on the divertor targets which are as much as ten times larger that the quiescent phase between ELMs. The divertor heat pulse is largest on the inner target, unlike that of L-Mode or quiescent H-mode; some tokamaks report radial structure in the heat flux profile which is suggestive of islands or helical structures. The power scaling of Type-1 ELM amplitude and frequency have been measured in several tokamaks and has recently been applied to predictions of the ELM Size in ITER. Concern over the expected ELM amplitude has led to a number of experiments aimed at demonstrating active control of ELMs. Impurity gas injection with feedback control on the radiation loss in ASDEX-U suggests that a promising mode of operation (the CDH-mode) with a very small type-3 ELMs can be maintained with heating power sell above the H-mode threshold, where giant type-1 ELMs can be maintained with heating power well above the H-mode threshold, where Giant type-1 ELMs are normally observed. While ELMs have many potential negative effects, the beneficial effect of ELMs in providing density control and limiting the core plasma impurity content in high confinement H- mode discharges should not be overlooked
Study of Type III ELMs in JET
No full textThis paper presents the results of JET experiments aimed at studying the operational space of plasmas with a Type III ELMy edge, in terms of both local and global plasma parameters. In JET, the Type III ELMy regime has a wide operational space in the pedestal n(e)-T-e diagram, and Type III ELMs are observed in standard ELMy H-modes as well as in plasmas with an internal transport barrier (ITB). The transition from an H-mode with Type III ELMs to a steady state Type I ELMy H-mode requires a minimum loss power, P-TypeI-P-TypeI decreases with increasing plasma triangularity. In the pedestal n(e)-T-e diagram, the critical pedestal temperature for the transition to Type I ELMs is found to be inversely proportional to the pedestal density (T-crit proportional to 1/n) at a low density. In contrast, at a high density, T-crit, does not depend strongly on density. In-the density range where T-crit proportional to 1/n, the critical power required for the transition to Type I ELMs decreases with increasing density. Experimental results are presented suggesting a common mechanism for Type III ELMs at low and high collisionality. A single model for the critical temperature for the transition from Type III to Type I ELMs, based on the resistive interchange instability with magnetic flutter, fits well the density and toroidal field dependence of the JET experimental data. On the other hand, this model fails to describe the variation of the Type III n(e)-T-e operational space with isotopic mass and q(95). Other results are instead suggestive of a different physics for Type III ELMs. At low collisionality, plasma current ramp experiments indicate a role of the edge current in determining the transition from Type III to Type I ELMs, while at high collisionality, a model based on resistive ballooning instability well reproduces, in term of a critical density, the experimentally observed q(95) dependence of the transition from Type I to Type III ELMs. Experimental evidence common to Type III ELMs in standard ELMy H-modes and in plasmas with ITBs indicates that they are driven by the same instability
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ELMs and the H-mode Pedestal in NSTX
No full textWe report on the behavior of ELMs in NBI-heated H-mode plasmas in NSTX. It is observed that the size of Type I ELMs, characterized by the change in plasma energy, decreases with increasing density, as observed at conventional aspect ratio. It is also observed that the Type I ELM size decreases as the plasma equilibrium is shifted from a symmetric double-null toward a lower single-null configuration. Type III ELMs have also been observed in NSTX, as well as a high-performance regime with small ELMs which we designate Type V. These Type V ELMs are consistent with high bootstrap current operation and density approaching Greenwald scaling. The Type V ELMs are characterized by an intermittent n=1 MHD mode rotating counter to the plasma current. Without active pumping, the density rises continuously through the Type V phase. However, efficient in-vessel pumping should allow density control, based on particle containment time estimates
Tolerable ELMs in conventional and advanced scenarios at ASDEX Upgrade
No full textRecent ASDEX Upgrade experiments integrated benign type II ELMs (tolerable peak heat loads on target plates) with high performance. In both conventional and advanced H-modes, the operation window with type II ELMs was extended towards q95 > 3.5 in close to double null configurations at sufficient high edge pedestal density above 50% of the Greenwald density. Type I ELMs are suppressed at almost constant pedestal parameters presumably due to a change in edge stability provided by higher edge magnetic shear, and at the same confinement level. Since conventional reactor designs are optimised at q95 around 3 operation with type II ELMs has to compensate the required higher q-value by advanced performance. This was achieved in advanced H-mode scenarios integrating high βN > 3.5, improved confinement via density peaking ( H98 - P = 1.3), and densities of 90% of Greenwald density with type II ELMs. Another way to mitigate ELMs is active type I ELM control by means of hydrogen or impurity injection. Using small hydrogen pellets we demonstrated an enhancement of the ELM frequency to almost the pellet rate of 20 Hz and a considerable reduction of the energy loss/ELM by more than a factor of 3
Tolerable ELMs in conventional and advanced scenarios at ASDEX Upgrade
No full textRecent ASDEX Upgrade experiments integrated benign type II ELMs (tolerable peak heat loads on target plates) with high performance. In both conventional and advanced H-modes, the operation window with type II ELMs was extended towards q95 > 3.5 in close to double null configurations at sufficient high edge pedestal density above 50% of the Greenwald density. Type I ELMs are suppressed at almost constant pedestal parameters presumably due to a change in edge stability provided by higher edge magnetic shear, and at the same confinement level. Since conventional reactor designs are optimised at q95 around 3 operation with type II ELMs has to compensate the required higher q-value by advanced performance. This was achieved in advanced H-mode scenarios integrating high βN > 3.5, improved confinement via density peaking ( H98 - P = 1.3), and densities of 90% of Greenwald density with type II ELMs. Another way to mitigate ELMs is active type I ELM control by means of hydrogen or impurity injection. Using small hydrogen pellets we demonstrated an enhancement of the ELM frequency to almost the pellet rate of 20 Hz and a considerable reduction of the energy loss/ELM by more than a factor of 3
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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