Comparative study on dynamic analyses of non-classically damped linear systems

Greco, Annalisa,Santini, Adolfo Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.6

In this paper some techniques for the dynamic analysis of non-classically damped linear systems are reviewed and compared. All these methods are based on a transformation of the governing equations using a basis of complex or real vectors. Complex and real vector bases are presented and compared. The complex vector basis is represented by the eigenvectors of the complex eigenproblem obtained considering the non-classical damping matrix of the system. The real vector basis is a set of Ritz vectors derived either as the undamped normal modes of vibration of the system, or by the load dependent vector algorithm (Lanczos vectors). In this latter case the vector basis includes the static correction concept. The rate of convergence of these bases, with reference to a parametric structural system subjected to a fixed spatial distribution of forces, is evaluated. To this aim two error norms are considered, the first based on the spatial distribution of the load and the second on the shear force at the base due to impulsive loading. It is shown that both error norms point out that the rate of convergence is strongly influenced by the spatial distribution of the applied forces.

Comparison between two geometrical nonlinear methods for truss analyses

Greco, M.,Menin, R.C.G.,Ferreira, I.P.,Barros, F.B. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.6

This paper presents a comparison between two different procedures to deal with the geometric nonlinear analysis of space trusses, considering its structural stability aspects. The first nonlinear formulation, called positional, uses nodal positions rather than nodal displacements to describe the finite elements kinematics. The strains are computed directly from the proposed position concept, using a Cartesian coordinate system fixed in space. The second formulation, called corotational, is based on the explicit separation between rigid body motion and deformed motion. The numerical examples demonstrate the performances and the convergence of the responses for both analyzed formulations. Two numerical examples were compared, including a lattice beam with postcritical behavior. Despite the two completely different approaches to deal with the geometrical nonlinear problem, the results present good agreement.

Lung Ultrasound to Evaluate Invasive Fungal Diseases after Allogeneic Hematopoietic Stem Cell Transplantation

Greco Raffaella,Lazzari Lorenzo,Xue Elisabetta,Assanelli Andrea,Marktel Sarah,Giglio Fabio,Clerici Daniela,Lupo Stanghellini Maria Teresa,Corti Consuelo,Bernardi Massimo,Ciceri Fabio,Peccatori Jacopo 대한감염학회 2019 Infection and Chemotherapy Vol.51 No.4

Invasive fungal diseases (IFDs) are a leading cause of infection-related-mortality after allogeneic hematopoietic stem cell transplantation (HSCT). In this prospective pilot study, we investigated the use of bedside lung ultrasound (US) in IFD management. Ten consecutive hematological patients, who developed pulmonary IFD after HSCT, were included in the study. Standard computed tomography scan and lung US were performed at IFD diagnosis and 10 days after antifungal treatment. The lung US demonstrated a high sensitivity in the detection of lung lesions at IFD diagnosis and in the follow-up examinations. It is of potential clinical relevance for IFD management in hematological patients.

Detection of a concentrated damage in a parabolic arch by measured static displacements

Greco, Annalisa,Pau, Annamaria Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.6

The present paper deals with the identification of a concentrated damage in an elastic parabolic arch through the minimization of an objective function which measures the differences between numerical and experimental values of static displacements. The damage consists in a notch that reduces the height of the cross section at a given abscissa and therefore causes a variation in the flexural stiffness of the structure. The analytical values of static displacements due to applied loads are calculated by means of the principle of virtual work for both the undamaged and damaged arch. First, pseudo-experimental data are used to study the inverse problem and investigate whether a unique solution can occur or not. Various damage intensities are considered to assess the reliability of the identification procedure. Then, the identification procedure is applied to an experimental case, where displacements are measured on a prototype arch. The identified values of damage parameters, i.e., location and intensity, are compared to those obtained by means of a dynamic identification technique performed on the same structure.

Effect of the Glucagon-Like Peptide-1 Receptor Agonists on Autonomic Function in Subjects with Diabetes: A Systematic Review and Meta-Analysis

Carla Greco,Daniele Santi,Giulia Brigante,Chiara Pacchioni,Manuela Simoni 대한당뇨병학회 2022 Diabetes and Metabolism Journal Vol.46 No.6

Background: In addition to the metabolic effects in diabetes, glucagon-like peptide 1 receptor (GLP-1R) agonists lead to a small but substantial increase in heart rate (HR). However, the GLP-1R actions on the autonomic nervous system (ANS) in diabetes remain debated. Therefore, this meta-analysis evaluates the effect of GLP-1R agonist on measures of ANS function in diabetes.Methods: According to the Cochrane Collaboration and Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement, we conducted a meta-analysis considering clinical trials in which the autonomic function was evaluated in diabetic subjects chronically treated with GLP-1R agonists. The outcomes were the change of ANS function measured by heart rate variability (HRV) and cardiac autonomic reflex tests (CARTs).Results: In the studies enrolled, HR significantly increased after treatment (<i>P</i><0.001), whereas low frequency/high frequency ratio did not differ (<i>P</i>=0.410); no changes in other measures of HRV were detected. Considering CARTs, only the 30:15 value derived from lying-to-standing test was significantly lower after treatment (<i>P</i>=0.002), but only two studies reported this measurement. No differences in other CARTs outcome were observed.Conclusion: The meta-analysis confirms the HR increase but seems to exclude an alteration of the sympatho-vagal balance due to chronic treatment with GLP-1R agonists in diabetes, considering the available measures of ANS function.

Selective Immunoglobulin A Deficiency in Type 1 Diabetes Mellitus: A Prevalence Study in Western Sicily (Italy)

Domenico Greco,Filippo Maggio 대한당뇨병학회 2015 Diabetes and Metabolism Journal Vol.39 No.2

Background: The association between type 1 diabetes and immunoglobulin A deficiency (IgA-D) has long been recognized in many populations. The aim of this study was to assess the prevalence of IgA-D in patients with type 1 diabetes mellitus all coming from a defined geographical area and to investigate the clinical features of these subjects. Methods: The records of 150 consecutive patients with type 1 diabetes mellitus referred in a period of one year were analyzed. A detailed history was obtained for each patient. Information was collected concerning age, gender, time of onset of diabetes, and presence of other autoimmune diseases. Results: Out of 150 patients with type 1 diabetes, eight (5.3%) had a diagnosis of IgA-D. There were one female and seven male; all these patients were diagnosed by screening: none of them had history of recurrent infections. Autoimmune thyroiditis was coexisting in five patients (62%). Although other associated autoimmune disorders were found in a number of patients, there was no different prevalence rate in IgA deficient patients. Conclusion: This study shows the prevalence of IgA-D in Sicilian patients with type 1 diabetes as 5.3% which is much higher than reported in other Italian studies. Moreover, our data show a high prevalence of IgA-D in male gender and describe thyroiditis as the most frequent autoimmune disease present in these patients. Finally, in our case report, IgA-D diagnosis always followed routine IgA measurement when case finding for celiac disease with no history of recurrent infections in each patient.

Detection of a concentrated damage in a parabolic arch by measured static displacements

Annalisa Greco,Annamaria Pau 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.6

The present paper deals with the identification of a concentrated damage in an elastic parabolic arch through the minimization of an objective function which measures the differences between numerical and experimental values of static displacements. The damage consists in a notch that reduces the height of the cross section at a given abscissa and therefore causes a variation in the flexural stiffness of the structure. The analytical values of static displacements due to applied loads are calculated by means of the principle of virtual work for both the undamaged and damaged arch. First, pseudo-experimental data are used to study the inverse problem and investigate whether a unique solution can occur or not. Various damage intensities are considered to assess the reliability of the identification procedure. Then, the identification procedure is applied to an experimental case, where displacements are measured on a prototype arch. The identified values of damage parameters, i.e., location and intensity, are compared to those obtained by means of a dynamic identification technique performed on the same structure.

Comparison between two geometrical nonlinear methods for truss analyses

M. Greco,R.C.G. Menin,I.P. Ferreira,F.B. Barros 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.6

This paper presents a comparison between two different procedures to deal with the geometric nonlinear analysis of space trusses, considering its structural stability aspects. The first nonlinear formulation, called positional, uses nodal positions rather than nodal displacements to describe the finite elements kinematics. The strains are computed directly from the proposed position concept, using a Cartesian coordinate system fixed in space. The second formulation, called corotational, is based on the explicit separation between rigid body motion and deformed motion. The numerical examples demonstrate the performances and the convergence of the responses for both analyzed formulations. Two numerical examples were compared, including a lattice beam with postcritical behavior. Despite the two completely different approaches to deal with the geometrical nonlinear problem, the results present good agreement.

Strength deterioration of reinforced concrete column sections subject to pitting

Rita Greco,Giuseppe Carlo Marano 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.4

Chloride induced reinforcement corrosion is widely accepted to be the most frequent mechanism causing premature degradation of reinforced concrete members, whose economic and social consequences are growing up continuously. Prevention of these phenomena has a great importance in structural design, and modern Codes and Standards impose prescriptions concerning design details and concrete mix proportion for structures exposed to different external aggressive conditions, grouped in environmental classes. This paper focuses on reinforced concrete column section load carrying capacity degradation over time due to chloride induced steel pitting corrosion. The structural element is considered to be exposed to marine environment and the effects of corrosion are described by the time degradation of the axial-bending interaction diagram. Because chlorides ingress and consequent pitting corrosion propagation are both time-dependent mechanisms, the study adopts a time-variant predictive approach to evaluate residual strength of corroded reinforced concrete columns at different lifetimes. Corrosion initiation and propagation process is modelled by taking into account all the parameters, such as external environmental conditions, concrete mix proportion, concrete cover and so on, which influence the time evolution of the corrosion phenomenon and its effects on the residual strength of reinforced concrete columns sections.

Comparative study on dynamic analyses of non-classically damped linear systems

Annalisa Greco,AdolfoSantini 국제구조공학회 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.6