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A genetic algorithm for the design of a fuzzy controller for active queue management
Active queue management (AQM) policies are those
policies of router queue management that allow for the detection of network congestion, the notification of such occurrences to the
hosts on the network borders, and the adoption of a suitable control
policy. This paper proposes the adoption of a fuzzy proportional
integral (FPI) controller as an active queue manager for Internet
routers. The analytical design of the proposed FPI controller is
carried out in analogy with a proportional integral (PI) controller,
which recently has been proposed for AQM. A genetic algorithm is
proposed for tuning of the FPI controller parameters with respect
to optimal disturbance rejection. In the paper the FPI controller
design metodology is described and the results of the comparison
with random early detection (RED), tail drop, and PI controller
are presented
DEFAULT MODE NETWORK AND WORKING MEMORY NETWORK DURING AN FMRI WORKING MEMORY TASK: DIFFERENCES AND CORRELATIONS WITH BEHAVIORAL PERFORMANCE
INTRODUCTION
Previous neuroimaging studies have shown that working memory load has marked effects on regional neural activation[1-5]. However, the mechanism through which working memory load modulates brain connectivity is still unclear. During a working memory task, two of the most involved networks are the default mode network (DMN) and the working memory network (WMN)[6-7]: the selective focus on these networks can be useful in better understanding the load effects. Spatial independent component analysis (ICA)[8] has becomes a reliable technique to investigate the networks involved during an fMRI task, as it extracts spatiotemporal patterns of neural activity maximizing spatial independence. A specific study, conducted with ICA, investigating on how the load and phase of a working memory task are related with the activation and response time, is nowadays lacking. The aim of this work is to use the time course of DMN and WMN, selected by means of ICA, for studying: a) how these networks are involved with the complexity of the task and the phase; b) how, in these networks, complexity and phase are correlated with reaction times. METHODS
MR Data Acquisition and preprocessing
Fifteen young adult healthy and right-handed were involved. The MR protocol consisted of one anatomical sequence 3D T1-weighted MP-RAGE (Voxel size: 1 x 1 x 1 mm) and three functional acquisitions of 15 minutes each performed with a T2*-weighted EPI sequence (TR/TE: 1500/30, In- plane resolution: 3.5x3.5 mm, Thickness: 3.5 mm, Nr of slices: 24, Field of view: 64 x 64 mm). All the images were collected with a Siemens Allegra 3T MR scanner (Siemens, Erlangen, Germany) and a standard head coil. During the fMRI acquisition the subjects performed a delayed spatial working memory paradigm presented with three levels of difficulty. The memory set consisted of one, three or five circles presented randomly in different locations and to the subjects were asked to judge whether or not a given target stimulus had been part of a previous memory stimulus set. Every experiment consisted of 90 working memory trials, 30 per load, divided in three runs. Data were analyzed with Brain Voyager QX. 2.4 (Brain Innovation, Maastricht, The Netherlands). FMRI preprocessing included: 3D head-motion correction, slice-scan time correction, spatial smoothing, temporal high pass filter and linear trend removal. Anatomic 3D data set was inhomogeneities corrected, filtered and transformed into Talairach coordinates and coregistered with the functional information.
Independent Component Analysis
This analysis was conducted using Brainvoyager QX 2.4. ICA analysis was performed on each subject\u2019s three functional acquisitions. A subsequent total ICA group analysis[9-10] was achieved by an inter- subject ICA group analysis of all the intra-subject ICA group analysis. From the obtained maps were selected two Independent Components (ICs) containing the WMN[1,2]: WMN1 defined by SPL and Precuneus, and WMN2 with DLPFC and IPS (Fig. 1b-c). Also one IC describing the DMN was considered, with PCC, IPL and MPFC (Fig. 1a)[11]. For each run of all the subjects the ICs time course was considered: three time windows of 3TR (4.5s) for each working memory task phase (encode, maintenance and retrieval) were selected taking into account the haemodynamic response by delaying the window of 5 volumes events from the start of every trial. The window time course was corrected for a baseline value. Mean values of the ICs where examined and a subsequent correlation between the mean values and the response time in every trial was estimated. A 3x3 two-way ANOVA on Fisher transformed correlation was conducted to test the variation of loads (load1=less complex, load3=more complex), phases and runs.
Figure 1: Networks selected from ICA analysis (transversal view): (a) DMN, (b) WMN1 (c) WMN2.
RESULTS
Figure 2 exhibits window mean activities and correlations divided for phase and load. DMN mean activity is negative while WMN1-2 mean activities have opposite behaviors regarding the phase, but similar concerning with the complexity (Fig. 2a-c). DMN shows a reduction of the correlation from encode to retrieval, instead of WM1-2 where it grows (Fig. 2d-f). The ANOVA showed significant variation for the phases over all the subjects in WMN1-2, an interaction of the variation of phases and runs in WMN2 and a interaction of phases, runs and loads in DMN. DISCUSSION These findings suggest that working memory networks (WMNs), as isolated by means of IC A, display substantially opposed mean values related to a different areas specialization. WMN1 seems to be more involved in the first part of the mnemonic phase and the amount of this involvement is associated to the trial: the more complicated the task, the higher the activation with respect to baseline. On the other hand, WMN2 increases from the first to the last part of the trial and is probably more involved in the operation of retrieval. In Figure 2e-f it is also shown that in the retrieval there is a stronger correlation between WMN1-2 mean values and the response time probably because this phase is the more complex. DMN exhibits, over all the phases, smaller than zero mean values (due to the task inducted deactivation). In contrast, its correlation has a different trend and increases above zero during the maintenance, probably due to the free thought of this phase. The different behavior of load 3 is probably due to the fact that this type of complexity is totally different from the other two. In conclusion, this study shows that, by means of ICA, it is possible to isolate networks of connected regions and relate their time courses to task phases and behavioral performance. This is a promising approach to advance the understanding of connectivity modulations in several brain networks, including WMNs and DMN
Response of microchannel plates to single particles and to electromagnetic showers
We report on the response of microchannel plates (MCPs) to single
relativistic particles and to electromagnetic showers. Particle detection by
means of secondary emission of electrons at the MCP surface has long been
proposed and is used extensively in ion time-of-flight mass spectrometers. What
has not been investigated in depth is their use to detect the ionizing
component of showers. The time resolution of MCPs exceeds anything that has
been previously used in calorimeters and, if exploited effectively, could aid
in the event reconstruction at high luminosity colliders. Several prototypes of
photodetectors with the amplification stage based on MCPs were exposed to
cosmic rays and to 491 MeV electrons at the INFN-LNF Beam-Test Facility. The
time resolution and the efficiency of the MCPs are measured as a function of
the particle multiplicity, and the results used to model the response to
high-energy showers.Comment: Paper submitted to NIM
Hardware prototyping and validation of a W-ΔDOR digital signal processor
Microwave tracking, usually performed by on ground processing of the signals coming from a spacecraft, represents a crucial aspect in every deep-space mission. Various noise sources, including receiver noise, affect these signals, limiting the accuracy of the radiometric measurements obtained from the radio link. There are several methods used for spacecraft tracking, including the Delta-Differential One-Way Ranging (ΔDOR) technique. In the past years, European Space Agency (ESA) missions relied on a narrowband ΔDOR system for navigation in the cruise phase. To limit the adverse effect of nonlinearities in the receiving chain, an innovative wideband approach to ΔDOR measurements has recently been proposed. This work presents the hardware implementation of a new version of the ESA X/Ka Deep Space Transponder based on the new tracking technique named Wideband ΔDOR (W-ΔDOR). The architecture of the new transponder guarantees backward compatibility with narrowband ΔDOR
Hemoperitoneum following mild blunt abdominal trauma: First presentation of Crohn's disease
Introduction: Inflammatory bowel diseases are heterogeneous in their presentation. Crohn's disease (CD) has been described as an unusual cause of massive lower gastrointestinal bleeding. We present a patient with CD whose first presentation was hemoperitoneum following mild blunt abdominal trauma Case presentation: A 54-year-old woman came to the emergency room with a blunt abdominal trauma. The patient underwent an abdominal CT scan with i.v. contrast medium injection, which showed hemoperitoneum with stenotic strictures of the small bowel and active massive bleeding from ileocolic artery. The rapid anemia onset and the CT report induced us to perform blood transfusion and an emergency exploratory laparotomy. Histological examination of the resected terminal ileum revealed a Crohn's disease. Discussion: Crohn's disease has been associated with hemoperitoneum, but to date there is no exact protocol regarding treatment of massive hemorrhagic Crohn's disease, which is rare. A conservative approach with medical therapy has been suggested for initial treatment. However, if medical treatment fails or bleeding continues even with intervention, bowel resection through surgical therapy should be performed
Photorefractive light needles in glassy nanodisordered KNTN
We study the formation of 2D self-trapped beams in nanodisordered potassium-sodium-tantalate-niobate (KNTN) cooled below the dynamic glass transition. Supercooling is shown to accelerate the photorefractive response and enhance steady-state anisotropy. Effects in the excited state are attributed to the anomalous slim-loop polarization curve typical of relaxors dominated by non-interacting polar-nano-regions
Influence of spatially heterogeneous deterioration patterns on strength and ductility of corroded reinforced concrete bridge piers
This work reports on some preliminary results obtained within the framework of a wide research project aimed to study the influence of the corrosion of in Reinforced Concrete (RC) piers on the overall seismic performances of bridges. In this context, after the statistical evaluation of a large database of real structures, a consistent set of bridges and piers has been selected as a sample representative of typical bridge profiles, pier heights and cross-sections as well as of material properties. In the first part of the project, pushover analyses of isolated piers with different corrosion patterns and intensity are carried out to evaluate the residual strength and ductility of corroded piers. In the second part, nonlinear static and dynamic seismic analyses of bridges with corroded piers are carried out to evaluate the influence of the deterioration on the overall seismic performance. Due to specific environmental conditions exposure or to water percolation from the superstructures, it is often the case that corrosion is non-uniformly distributed over piers producing non-homogeneous spatial deterioration patterns. The nonlinear modeling of this type of situations represents specific challenges related to the description of the deterioration patterns and the calibration of material properties. To this end, a multi-level modeling approach based on fiber-based finite elements has been developed and implemented in a specific OpenSeesPy software that allows users to accurately model RC piers subject to arbitrary corrosion patterns, up to their ultimate limit states. In this work, a specific case study of a typical RC rectangular hollow bridge extracted from the mentioned above database subject to different corrosion intensity and patterns is studied. In particular, the influence of the corrosion-induced deterioration on residual strength and ductility are studied. Results show that depending on the intensity and on the patterns significant variations of both strength and ductility can be observed with respect to the undamaged conditions
Swallowing evaluation with videofluoroscopy in the paediatric population
Paediatric swallowing disorders can have several causes, from prematurity and congenital anomalies to gastro-oesophageal reflux and
infective or inflammatory pathologies of the upper digestive tract. In neonates, the swallowing process is reflexive and involuntary. Later
in infancy, the oral phase comes under voluntary control, while the pharyngeal phase and oesophageal phases remain involuntary. Swallowing difficulties can severely compromise pulmonary health and nutritional intake of paediatric patients. Videofluoroscopic Swallow Study
(VFSS) is a radiographic procedure that provides a dynamic view of the swallowing process and is frequently considered to be definitive
evaluation for objective assessment of dysphagia in paediatric patients. This review focuses on the different possible aetiologies of paediatric swallowing disorders and related videofluoroscopic swallowing study procedures and appearances
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