Abstract The application of vibration-based Structural Health Monitoring (SHM) for damage detection is characterised by three fundamental aspects: the features extracted as representative of the ...structural condition that can be directly linked to some form of damage, the metrics selected as novelty or damage index, and the statistical model or classifier built to identify underlying patterns indicative of changes in the structure’s state. Focusing on the first step to improve the performance of vibration-based SHM strategies, the extracted features should be robust to noise, sensitive to the presence of a specific type of damage. Further, damage should induce patterns that are distinguishable from environmental and operational variabilities and other forms of damage such as ageing phenomena. In this paper, the problem is framed as an outlier detection problem and the the use of different modal parameters as Damage Sensitive Features (DSFs) is investigated, evaluating them based on the detection performance of an unsupervised One-Class Support Vector Machine (OCSVM) classifier. In particular, an artificial dataset is generated from the calibrated numerical model of a three-storey steel frame structure in different damage scenarios. The methodology is validated against available experimental data. For the case investigated the natural frequencies were sensitive to damage and robust to noise.
Purpose
To retrospectively assess safety and potential effectiveness of percutaneous intervertebral disc coagulation therapy (PDCT) using plasma thermal reaction for the treatment of lumbar and ...cervical disc hernias resistant to medical therapy.
Materials and Methods
Forty-four patients (age range 18–87 years, mean 52.7) with contained and extruded symptomatic lumbar (
N
= 48) and cervical (
N
= 6) disc hernias in the absence of free fragments causing radiculopathy without improvement after 6-week conservative therapy were enrolled. Pretreatment discography has been performed in every patient. Spine MRI was performed before the procedure and 4 months later, in order to check post-PDCT changes. Technical success was defined as correct placement of PDCT fiber
;
clinical outcomes were evaluated using visual analog scale (VAS) and the Oswestry Disability Index (ODI) before the procedure and after 4 months.
Results
A total of 54 levels have been treated with 98% technical success; in 12 patients (27%), the treatment was performed in two levels at the same time. All patients well tolerated the procedure; most patients (
N
= 39; 89%) had significant improvement in symptoms, with ODI score reduction from 47.61 ± 8.7 to 13.38 ± 9.4 (
p
< 0.001). The mean pre-PDCT VAS score was 7.47 ± 0.8. VAS score was decreased down to 1.36 ± 1.6 at final follow-up (
p
< 0.001). There were no cases of infection, nerve damage, or bleeding.
Conclusions
PDCT can be an effective and safe for minimally invasive indirect decompression for cervical and lumbar hernia resistant to conservative treatment, particularly when patients are correctly selected.
This paper discusses on the output only modal identification of historic structures. Modal identification has been carried out both in frequency and in time domain using the Frequency Domain ...Decomposition (FDD) and the Stochastic Subspace Iteration (SSI-data) respectively. To highlight the sensitivity of the two methods, two masonry towers under different environmental loads have been considered. In one case the dynamic excitation can be assumed as a very weak random white noise, in the other case, probably due the several external noises, the ambient noise is locally dominated by several harmonic forces. The paper highlights the challenges in the modal identification of heritage structures such as the very low weak operating response and the role of the harmonics originated by engines operating somewhere nearby the structures. Moreover, it is investigated the information trade-off between the frequency domain and the time domain identification for evaluating the modal properties of the structures in a straightforward manner.
The conservation of Cultural Heritage (CH) requires the integration of experimental data in the computational models in order to improve the robustness of the structural analyses. In this scenario, ...the paper introduces recent results of experimental activities carried out on the Galleria dell’Accademia di Firenze (GDA-FI), a famous Italian museum complex. The work aims to investigate the dynamic behaviour of one of the Structural Units (SU) which compose the museum: the Tribuna, where the Michelangelo’s David is exhibited to the public. The experimental layout was composed by two triaxial stations roving in different positions carefully designed by considering both the architectonic features of the structure and the location of the masterpieces collected in the Tribuna, such as paintings and sculptures, which could not be moved during the measurements. The investigation activity was performed in the framework of a wider research project, DAVID "Defense of cultural heritage and Assessment of Vulnerability through Innovative technologies & Device", co-founded by Tuscany Region and Galleria dell’Accademia di Firenze with the aim to preserve the museum complex and the works of art inside. A computational model is herein proposed to illustrate the process of calibration, and its advantages in terms of model reliability, through the comparison between the experimental results and the model output itself. More in detail, the research deal with the issue related to the analyses of a portion of the structure, extracted from the whole complex, and the boundary conditions which need to be assigned in order to represent the actual interaction with the surrounding buildings. The workflow discussed in this paper is applied to the case study of GDA-FI and it represents a meaningful test bench in order to draw general remarks on the topic of historical museum complex conservation as well as the employment of Historical Building Information Modelling (HBIM) to link different sources of information to the computational models.
In this paper, the skin effect on a solid copper wire is studied. The AC resistance is analysed by Finite Element Method (FEM) and the results are compared with an analytical model available in ...literature. As a particular case study, a Wireless Power Transfer (WPT) system is used. The hollow wire is proposed as a possible solution for the minimization of the cross-section area with low current density due to the high frequency operation. An empirical formula that relates the optimum thickness and the operating frequency is proposed. The advantages and disadvantages of the hollow wire are then discussed.
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Monoallelic mutations on TMEM63A have been recently reported as cause of a previously unrecognized disorder named "infantile-onset transient hypomyelination". Clinical and neuroradiological ...presentation is described as highly similar to Pelizaeus-Merzbacher Disease but evolution over time was surprisingly benign with a progressive spontaneous improving course. We report on a new TMEM63A-mutated girl. The clinical picture was similar to the one already described except for the presence of recurrent episodes of unilateral eyelid twitching, and for the evidence of spinal cord involvement on MRI. These are interesting findings helping in distinguishing this condition from classic PMD since early disease stages. However, additional observations are needed to confirm if these are common features of this condition.
r-fat linearized polynomials over finite fields Bartoli, Daniele; Micheli, Giacomo; Zini, Giovanni ...
Journal of combinatorial theory. Series A,
July 2022, 2022-07-00, Volume:
189
Journal Article
Peer reviewed
Open access
r-fat polynomials are a natural generalization of scattered polynomials. They define linear sets of the projective line PG(1,qn) of rank n with r points of weight larger than one. Using techniques on ...algebraic curves and function fields, we obtain numerical bounds for r and the non-existence of exceptional r-fat polynomials with r>0. We completely determine the possible values of r when considering linearized polynomials over Fq4 and we also provide one family of 1-fat polynomials in PG(1,q5). Furthermore, we investigate LP-polynomials (i.e. polynomials of type f(x)=x+δxq2s∈Fqnx, gcd(n,s)=1), determining the spectrum of values r for which such polynomials are r-fat.
Background and purpose
The best reperfusion treatment for patients with mild acute ischaemic stroke harbouring proximal anterior circulation large vessel occlusion (LVO) is unknown. The aim was to ...compare the safety and efficacy of intravenous thrombolysis (IVT) plus endovascular thrombectomy (EVT) versus IVT alone in LVO patients with mild symptoms.
Methods
From the Safe Implementation of Treatment in Stroke–International Stroke Thrombolysis and Thrombectomy Register (SITS‐ISTR), were included: (i) consecutive acute ischaemic stroke patients, (ii) treated within 4.5 h from symptoms onset, (iii) baseline National Institutes of Health Stroke Scale (NIHSS) score ≤5 and (iv) intracranial internal carotid artery ICA, M1 or T occlusion defined as occlusion of ICA terminal bifurcation. After propensity score matching, 3‐month functional outcomes (modified Rankin Scale mRS 0–1 and 0–2) and safety outcomes (symptomatic intracerebral haemorrhage and death) were compared (via univariable and multivariable logistic and ordinal regression analyses) in patients treated with IVT + EVT versus IVT alone.
Results
In all, 1037 patients were included. After propensity score matching (n = 312 per group), IVT + EVT was independently associated with poor functional outcomes (adjusted odds ratio aOR 0.46 for mRS 0–1, 95% confidence interval CI 0.30–0.72, p = 0.001; aOR 0.52 for mRS 0–2, 95% CI 0.32–0.84, p = 0.007; aOR 1.61 for 1‐point shift in mRS score, 95% CI 1.12–2.32, p = 0.011), with no significant differences in safety outcomes compared to IVT alone, despite numerically higher rates of symptomatic intracerebral haemorrhage (3.3% vs. 1.1%; p = 0.082), a higher rate of any haemorrhagic transformation (17.6% vs. 7.3%; p < 0.001) and subarachnoid haemorrhage (7.9% vs. 1.5%; p = 0.002) in the IVT + EVT group.
Discussion
In anterior circulation LVO patients presenting with NIHSS score ≤5, IVT + EVT (vs. IVT alone) was associated with poorer 3‐month functional outcome. Randomized controlled trials are needed to elucidate the best treatments in mild LVO patients.
•Three closely spaced springs follow different underground karst conceptual models.•The karstified network is more interconnected and more active during high flow.•Use of fluorescent dyes in ...extensive alpine karst aquifers may be ineffective.•Monitoring of natural tracers in extensive alpine karst aquifers is very effective.
Limestone massifs with a high density of dolines form important karst aquifers in most of the Alps, often with groundwater circulating through deep karst conduits and water coming out of closely spaced springs with flow rates of over some cubic meters per second. Although several hydrogeological studies and tracing experiments were carried out in many of these carbonate mountains in the past, the hydrogeology of most of these karst aquifers is still poorly known.
Geological, hydrodynamic and hydrochemical investigations have been carried out in one of the most representative of these areas (Cansiglio-Monte Cavallo, NE Italy) since spring 2015, in order to enhance the knowledge on this important type of aquifer system. Additionally, a cave-to-spring multitracer test was carried out in late spring 2016 by using three different fluorescent tracers. This hydrogeological study allowed: 1) gathering new detailed information on the geological and tectonic structure of such alpine karst plateau; 2) defining discharge rates of the three main springs (Gorgazzo, Santissima, and Molinetto) by constructing rating curves; 3) understanding the discharging behavior of the system with respect to different recharge conditions; 4) better defining the recharge areas of the three springs.
The three nearby springs (the spring front stretches over 5 km), that drain the investigated karst aquifer system, show different behaviors with respect to changing discharge conditions, demonstrating this aquifer to be divided in partially independent drainage systems under low-flow conditions, when their chemistry is clearly differentiated. Under high-flow conditions, waters discharging at all springs show more similar geochemical characteristics. The combination of geochemistry, hydrodynamic monitoring and dye tracing tests has shown that the three springs have different recharge areas. The study points out that even closely spaced karst springs, that apparently drain the same karst mountain, can have different behaviors, and thus distinctive reactions toward polluting events, a characteristic to be taken into account for their management.
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