Search results for "Contrast"
showing 10 items of 1162 documents
Using penalties instead of rewards: Solving OCST problems with guided local search
2012
Abstract This paper considers the optimal communication spanning tree (OCST) problem. Previous work analyzed features of high-quality solutions and found that edges in optimal solutions have low weight and point towards the center of a tree. Consequently, integrating this problem-specific knowledge into a metaheuristic increases its performance for the OCST problem. In this paper, we present a guided local search (GLS) approach which dynamically changes the objective function to guide the search process into promising areas. In contrast to traditional approaches which reward promising solution features by favoring edges with low weights pointing towards the tree’s center, GLS penalizes low-…
The squared symmetric FastICA estimator
2017
In this paper we study the theoretical properties of the deflation-based FastICA method, the original symmetric FastICA method, and a modified symmetric FastICA method, here called the squared symmetric FastICA. This modification is obtained by replacing the absolute values in the FastICA objective function by their squares. In the deflation-based case this replacement has no effect on the estimate since the maximization problem stays the same. However, in the symmetric case we obtain a different estimate which has been mentioned in the literature, but its theoretical properties have not been studied at all. In the paper we review the classic deflation-based and symmetric FastICA approaches…
Advantages of fitting contrast curves using logistic function: a technical note.
2013
Objective The aim of this article is to demonstrate how the contrast properties of an imaging system can be ideally fitted with the use of stripe patterns and the logistic function. Study Design Stripe patterns with defined amounts of line pairs (lp/mm) per mm (10-20 lp/mm) were recorded with the use of digital photostimulable storage phosphor. Scan data and normalized image data were analyzed with the use of ImageJ and MatLab to calculate different contrast curves. Results For original scan data, the goodness of fit was 0.0000019 (sum of squared error [SSE]). The R-square was 0.9998. For normalized data the goodness of fit was 0.0007 (SSE) and the R-square 0.998. An amount of 50% contrast …
Dynamics of Quadriceps Muscles during Isometric Contractions : Velocity-Encoded Phase Contrast MRI Study
2021
Objective: To quantify the spatial heterogeneity of displacement during voluntary isometric contraction within and between the different compartments of the quadriceps. Methods: The thigh muscles of seven subjects were imaged on an MRI scanner while performing isometric knee extensions at 40% maximal voluntary contraction. A gated velocity-encoded phase contrast MRI sequence in axial orientations yielded tissue velocity-encoded dynamic images of the four different compartments of the thigh muscles (vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), and rectus femoris (RF)) at three longitudinal locations of the proximal–distal length: 17.5% (proximal), 50% (middle), and 7…
Contrast-Enhanced Ultrasound Qualitative and Quantitative Characteristics of Parathyroid Gland Lesions
2021
Background and Objectives: preoperative differentiation of enlarged parathyroid glands may be challenging in conventional B-mode ultrasound. The aim of our study was to analyse qualitative and quantitative characteristics of parathyroid gland lesions, using multiparametric ultrasound protocol—B-mode, Colour Doppler (CD), and contrast-enhanced ultrasound (CEUS)—and to evaluate correlation with morphology in patients with hyperparathyroidism (HPT). Materials and Methods: consecutive 75 patients with 88 parathyroid lesions and biochemically confirmed HPT prior to parathyroidectomy were enrolled in the prospective study. B-mode ultrasound, CD, and CEUS were performed with the subsequent qualita…
Focal Pancreatic Lesions: Role of Contrast-Enhanced Ultrasonography.
2021
The introduction of contrast-enhanced ultrasonography (CEUS) has led to a significant improvement in the diagnostic accuracy of ultrasound in the characterization of a pancreatic mass. CEUS, by using a blood pool contrast agent, can provide dynamic information concerning macro- and micro-circulation of focal lesions and of normal parenchyma, without the use of ionizing radiation. On the basis of personal experience and literature data, the purpose of this article is to describe and discuss CEUS imaging findings of the main solid and cystic pancreatic lesions with varying prevalence.
I traffici illeciti nel Mediterraneo. Persone, stupefacenti, tabacco
2019
Attraverso la combinazione di ricerca criminologica e giuridico-normativa, e grazie anche alla collaborazione con esperti esterni (studiosi, magistrati, rappresentanti di istituzioni italiane e straniere), la ricerca da cui scaturisce il volume ha indagato le interazioni tra i diversi traffici illeciti e la criminalità organizzata nel bacino del Mediterraneo. In tale area, storicamente cruciale per la mobilità di persone e di beni, l’attenzione si è rivolta in particolare ai fenomeni del traffico e della tratta di persone, del traffico di stupefacenti e del contrabbando di sigarette. I contributi raccolti – unitamente al rapporto criminologico e ai cinque rapporti nazionali accessibili su w…
More About the Musical Expertise of Musically Untrained Listeners
2003
Several behavioral experiments that were designed to compare the abilities of musicians and nonmusicians to process subtle changes in musical structures are surveyed. These experiments deal with different aspects of music perception including the processing of melodic and harmonic structures, the processing of large-scale structures, and implicit learning. In all these experiments, the so-called nonmusician listeners behaved in a very similar way as did highly trained students from music conservatories and music departments. This outcome suggests that when the experimental setting requires participants to process musical structures (in contrast to musical tones), the large audience of untra…
Does Pathological Aging Affect Musical Learning and Memory?
2012
the effect of pathological aging on explicit memory is very well documented, but relatively few studies have addressed this issue in the musical domain. To examine learning and consolidation of melodies, we designed a melodic recognition task involving immediate and delayed recognition of 16 target melodies (8 familiar and 8 unfamiliar). Seventeen patients with mild to moderate Alzheimer's disease (AD) and 17 age-matched controls were tested. During the initial presentation of the targets, the participant had to decide whether or not the melody was familiar. Recognition was tested after one and three presentations of the target melodies using a yes/no recognition paradigm. Delayed recogniti…
Self-regulation Training and Job Search Behavior: A Natural Field Experiment Within an Active Labor Market Program
2019
Recent evidence suggests that self-regulation abilities play an important role for the job finding success of unemployed persons. We conduct a randomized controlled trial embedded in an established labor market reactivation program to examine the effect of a self-regulation training on job search effort of long-term unemployed participants. Our treatment involves teaching a self-regulation strategy based on mental contrasting with implementation intentions. We find that the treatment has a positive effect on the quality of application documents as well as on the probability of participants submitting their documents on time. However, we do not find a significant positive effect on labor mar…