3,474 research outputs found
Excited states in bilayer graphene quantum dots
We report on ground- and excited state transport through an electrostatically
defined few-hole quantum dot in bilayer graphene in both parallel and
perpendicular applied magnetic fields. A remarkably clear level scheme for the
two-particle spectra is found by analyzing finite bias spectroscopy data within
a two-particle model including spin and valley degrees of freedom. We identify
the two-hole ground-state to be a spin-triplet and valley-singlet state. This
spin alignment can be seen as Hund's rule for a valley-degenerate system, which
is fundamentally different to quantum dots in carbon nano tubes and GaAs-based
quantum dots. The spin-singlet excited states are found to be valley-triplet
states by tilting the magnetic field with respect to the sample plane. We
quantify the exchange energy to be 0.35meV and measure a valley and spin
g-factor of 36 and 2, respectively
Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution
Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads
to tolerable heat and particle loads on the wall is a major challenge. The new European
medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade
(AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide
parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal
and SOL parameters are not achievable simultaneously in present day devices. A two prong
approach is adopted. On the one hand, scenarios with tolerable transient heat and particle
loads, including active edge localised mode (ELM) control are developed. On the other hand,
divertor solutions including advanced magnetic configurations are studied. Considerable
progress has been made on both approaches, in particular in the fields of: ELM control with
resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control,
as well as filamentary scrape-off-layer transport. For example full ELM suppression has now
been achieved on AUG at low collisionality with n = 2 RMP maintaining good confinement
HH(98,y2) 0.95. Advances have been made with respect to detachment onset and control.
Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor)
shed new light on SOL physics. Cross field filamentary transport has been characterised in a
wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental
understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the
SOL also play a crucial role for ELM stability and access to small ELM regimes.European Commission (EUROfusion 633053
Scrape-off layer heat transport and divertor power deposition of pellet-induced edge localized modes
Simulation of Main Memory Database Recovery
In a main memory database (MMDB), the primary copy of the database may reside permanently in a volatile memory. When a system failure occurs, the database must be reloaded efficiently from archive memory into main memory. This paper presents four different reload schemes and the simulation models constructed to compare the algorithms. Simulation results indicate that the reload scheme based on freguency of data access gives the best overall performance in terms of transaction response time and system throughput.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
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