445 research outputs found
Preliminary observation on use of nest boxes in protected areas of Southern Sicily
In this short note we summarize the data self-made nesting in nest boxes in two areas
of NATURA 2000 in southern Sicily. The models of nest boxes considered host species during
the study the following period: Falco naumanni, Falco tinnunculus, Athene noctua, Strix aluco,
Sturnus unicolor, Parus major, Certhia brachydactyla, Corvus monedula, Passer montanus
An equilibrium model for RFP plasmas in the presence of resonant tearing modes
The equilibrium of a finite-beta RFP plasma in the presence of
saturated-amplitude tearing modes is investigated. The singularities of the MHD
force balance equation JXB=grad(p) at the modes rational surfaces are resolved
through a proper regularization of the zeroth-order (equilibrium) profiles, by
setting to zero there the gradient of the pressure and parallel current
density. An equilibrium model, which satisfies the regularization rule at the
various rational surfaces, is developed. The comparison with the experimental
data from the Reversed Field eXperiment (RFX) gives encouraging results. The
model provides an easy tool for magnetic analysis: many aspects of the
perturbations can be analyzed and reconstructed.Comment: Final accepted version. 36 page
Nanostructured Lead Electrodes with Reduced Graphene Oxide for High-Performance LeadâAcid Batteries
Nanostructured Pb electrodes consisting of nanowire arrays were obtained by electrodeposition, to be used as negative electrodes for leadâacid batteries. Reduced graphene oxide was added to improve their performances. This was achieved via the electrochemical reduction of graphene oxide directly on the surface of nanowire arrays. The electrodes with and without reduced graphene oxide were tested in a 5 M sulfuric acid solution using a commercial pasted positive plate and an absorbed glass mat separator in a zero-gap configuration. The electrodes were tested in deep cycling conditions with a very low cut-off potential. Chargeâdischarge tests were performed at 5C. The electrode with reduced graphene oxide outperformed the electrode without reduced graphene oxide, as it was able to work with a very high utilization of active mass and efficiency. A specific capacity of 258 mAhgâ1âvery close to the theoretical oneâwas achieved, and the electrode lasted for more than 1000 cycles. On the other hand, the electrode without reduced graphene oxide achieved a capacity close to 230 mAhgâ1, which corresponds to a 90% of utilization of active mass
An active feedback recovery technique from disruption events induced by m=2 n=1 tearing modes in ohmically heated tokamak plasmas
We present experimental results of magnetic feedback control on the m=2, n=1
tearing mode in RFX-mod operated as a circular ohmically heated tokamak. The
feedback suppression of the non-resonant m=2, n=1 Resistive Wall Mode (RWM) in
q(a)<2 plasmas is a well-established result of RFX-mod. The control of the
tearing counterpart, which develops in q(a)>2 equilibrium, is instead a more
difficult issue. In fact, the disruption induced by a growing amplitude m=2,
n=1 tearing mode can be prevented by feedback only when the resonant surface
q=2 is close to the plasma edge, namely 2<q(a)<2.5, and the electron density
does not exceed approximately half of the Greenwald limit. A combined technique
of tearing mode and q(a) control has been therefore developed to recover the
discharge from the most critical conditions: the potentially disruptive tearing
mode is converted into the relatively benign RWM by suddenly decreasing q(a)
below 2. The experiments demonstrate the concept with 100% of successful cases.
The q(a) control has been performed through the plasma current, given the
capability of the toroidal loop-voltage power supply of RFX-mod. We also
propose a path for controlling q(a) by acting on the plasma shape, which could
be applied to medium size elongated tokamaks
The plasma boundary in Single Helical Axis RFP plasmas
Single Helical Axis (SHAx) states obtained in high current reversed field
pinch (RFP) plasmas display, aside from a dominant mode in the m=1 spectrum,
also a dominant m=0 mode, with the same toroidal mode number as the m=1 one.
The two modes have a fixed phase relationship. The island chain created by the
m=0 mode across the reversal surface gives rise, at shallow reversal of the
toroidal field, to an X-point structure which separates the last closed flux
surface from the first wall, creating a divertor-like configuration. The
plasma-wall interaction is found to be related to the connection length of the
field lines intercepting the wall, which displays a pattern modulated by the
dominant mode toroidal periodicity. This configuration, which occurs only for
shallow toroidal field reversal, could be exploited to realize an island
divertor in analogy to stellarators.Comment: 12 pages, 9 figures Submitted to Nuclear Fusio
Contrastive Language-Image Pretrained Models are Zero-Shot Human Scanpath Predictors
Understanding the mechanisms underlying human attention is a fundamental
challenge for both vision science and artificial intelligence. While numerous
computational models of free-viewing have been proposed, less is known about
the mechanisms underlying task-driven image exploration. To address this gap,
we present CapMIT1003, a database of captions and click-contingent image
explorations collected during captioning tasks. CapMIT1003 is based on the same
stimuli from the well-known MIT1003 benchmark, for which eye-tracking data
under free-viewing conditions is available, which offers a promising
opportunity to concurrently study human attention under both tasks. We make
this dataset publicly available to facilitate future research in this field. In
addition, we introduce NevaClip, a novel zero-shot method for predicting visual
scanpaths that combines contrastive language-image pretrained (CLIP) models
with biologically-inspired neural visual attention (NeVA) algorithms. NevaClip
simulates human scanpaths by aligning the representation of the foveated visual
stimulus and the representation of the associated caption, employing
gradient-driven visual exploration to generate scanpaths. Our experimental
results demonstrate that NevaClip outperforms existing unsupervised
computational models of human visual attention in terms of scanpath
plausibility, for both captioning and free-viewing tasks. Furthermore, we show
that conditioning NevaClip with incorrect or misleading captions leads to
random behavior, highlighting the significant impact of caption guidance in the
decision-making process. These findings contribute to a better understanding of
mechanisms that guide human attention and pave the way for more sophisticated
computational approaches to scanpath prediction that can integrate direct
top-down guidance of downstream tasks
Radiomics-Based Inter-Lesion Relation Network to Describe [18F]FMCH PET/CT Imaging Phenotypes in Prostate Cancer
Advanced image analysis, specifically radiomics, has been recognized as a potential source of biomarkers for cancers. However, there are challenges to its application in the clinic, such as proper description of diseases where multiple lesions coexist. In this study, we aimed to characterize the intra-tumor heterogeneity of metastatic prostate cancer using an innovative approach. This approach consisted of a transformation method to build a radiomic profile of lesions extracted from [18F]FMCH PET/CT images, a qualitative assessment of intra-tumor heterogeneity of patients, and a quantitative representation of the intra-tumor heterogeneity of patients in terms of the relationship between their lesionsâ profiles. We found that metastatic prostate cancer patients had lesions with different radiomic profiles that exhibited intra-tumor radiomic heterogeneity and that the presence of many radiomic profiles within the same patient impacted the outcome
Resistive g-modes in a reversed field pinch plasma
First direct experimental evidence of high frequency, high toroidal mode
number (n>20), magnetic fluctuations due to unstable resistive interchange
modes (g-modes) resonant in the edge region of a reversed field pinch (RFP)
plasma is presented. Experimental characterization of time and space
periodicities of the modes is provided by means of highly resolved in-vessel
edge and insertable magnetic diagnostics. It is found that the spectral mode
properties are in good agreement with the predictions of the theoretical linear
resistive magnetohydrodynamic stability analysis. A simple model is proposed
for the observed saturation levels of the modes.Comment: Submitted to Physical Review Letter
Statistical features of edge turbulence in RFX-mod from Gas Puffing Imaging
Plasma density fluctuations in the edge plasma of the RFX-mod device are
measured through the Gas Puffing Imaging Diagnostics. Statistical features of
the signal are quantified in terms of the Probability Distribution Function
(PDF), and computed for several kinds of discharges. The PDFs from discharges
without particular control methods are found to be adequately described by a
Gamma function, consistently with the recent results by Graves et al [J.P.
Graves, et al, Plasma Phys. Control. Fusion 47, L1 (2005)]. On the other hand,
pulses with external methods for plasma control feature modified PDFs. A first
empirical analysis suggests that they may be interpolated through a linear
combination of simple functions. An inspection of the literature shows that
this kind of PDFs is common to other devices as well, and has been suggested to
be due to the simultaneous presence of different mechanisms driving
respectively coherent bursts and gaussian background turbulence. An attempt is
made to relate differences in the PDFs to plasma conditions such as the local
shift of the plasma column. A simple phenomenological model to interpret the
nature of the PDF and assign a meaning to its parameters is also developed.Comment: 27 pages. Published in PPC
Signatures of non-Markovian turbulent transport in Reversed Field Pinch plasmas
Transport of field lines is studied for a realistic model of magnetic field
configuration in a Reversed Field Pinch. It is shown that transport is
anomalous, i.e., it cannot be described within the standard diffusive paradigm.
To fit numerical results we present a transport model based upon the Continuous
Time Random Walk formalism. Fairly good quantitative agreement appears for
exponential memory functions.Comment: 20 pages. Submitte
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