Comparison of Model Order Reduction Techniques for Flexible Multibody Dynamics using an Equivalent Rigid-Link System Approach

In this paper we present a comparison of different model order reduction techniques for flexible multibody dynamics. In particular, we adopt a formulation based on a Equivalent Rigid-Link System (ERLS). This approach is suitable in the case of large displacements and small elastic deformations and it allows the kinematic equations of motion to be decoupled from the compatibility equations of the displacements at the joints. The ERLS approach, recently extended through a modal formulation, is here implemented in combination with different reduction techniques, i.e. Craig- Bampton, Interior Mode Ranking (IMR), Guyan, Least Square Model Reduction (LSMR) and Mode Displacement Method (MDM). In order to assess the advantages and disadvantages of the different methodologies, these techniques are applied to a benchmark mechanism under different input conditions, i.e. gravitational force and step torque input. The accuracy of each reduced model is numerically evaluated through the comparison of computational time, the behaviour in frequency domain and by means of vector correlation methods, i.e. the Modal Assurance Criterion (MAC), the Cross-Orthogonality (CO) and the Normalized Cross-Orthogonality (NCO)

insights into the definition of terms in european medical device regulation

ABSTRACTIntroduction: Medical devices comprise apparatus/instruments, software, and materials with therapeutic activities obtained by principal mechanisms of action different from pharmacological, immunological and metabolic, which are proper of medicinal products. In this context the key for the distinction between medicinal products and devices lies in the correct interpretation of these terms, which, although defined in a guideline, are still not univocally interpreted.Areas covered: This article discusses the definitions of pharmacological and non-pharmacological mechanisms of action, such as the chemical and physical means. The aim is to give insights on the correct definition these terms in order to contribute to build the desired synergy between scientific and regulatory fields and promote a correct interpretation of the European regulatory framework as well as sustainable health and innovation.Expert commentary: We propose a series of definitions and a method to interpret those definitions within ..

Modeling the vibration of spatial flexible mechanisms through an equivalent rigid-link system/component mode synthesis approach

In this paper, a novel formulation for modeling the vibration of spatial flexible mechanisms and robots is introduced. The formulation is based on the concepts of equivalent rigid-link system (ERLS) that allows kinematic equations of motion for the ERLS decoupled from the compatibility equations of the displacement at the joint to be written. With respect to the available literature, in which the ERLS concept has been proposed together with a finite element method (FEM) approach (ERLS-FEM), the formulation is extended in this paper through a modal approach and, in particular, a component mode synthesis technique which allows a reduced-order system of dynamic equations to be maintained even when a fine discretization is needed. The model is validated numerically by comparing it with the results obtained from the Adams-Flex\u2122 software, which implements the well-known floating frame of reference approach for a benchmark L-shaped mechanism. A good agreement between the two models is shown

Experimental Validation of a Dynamic Model for Lightweight Robots

Nowadays, one of the main topics in robotics research is dynamic performance improvement by means of a lightening of the overall system structure. The effective motion and control of these lightweight robotic systems occurs with the use of suitable motion planning and control process. In order to do so, model-based approaches can be adopted by exploiting accurate dynamic models that take into account the inertial and elastic terms that are usually neglected in a heavy rigid link configuration. In this paper, an effective method for modelling spatial lightweight industrial robots based on an Equivalent Rigid Link System approach is considered from an experimental validation perspective. A dynamic simulator implementing the formulation is used and an experimental test-bench is set-up. Experimental tests are carried out with a benchmark L-shape mechanism

Apparent diffusion coefficient values in borderline breast lesions upgraded and not upgraded at definitive histopathological examination after surgical excision

Purpose: The study aims were to evaluate if the apparent diffusion coefficient (ADC) value could distinguish between breast lesions classified as B3 at core needle biopsy (CNB) that show or do not show atypia or malignancy at definitive histopathological examination (DHE) after surgical excision. Material and methods: From January 2013 to December 2017, 141 patients with a B3 breast lesion underwent magnetic resonance imaging and were included in the study. The ADC value was assessed drawing a ROI outlining the entire lesion, evaluating the mean ($ADC_{mean}$) and minimum ADC values ($ADC_{min}$). Results: Both $ADC_{mean}$ and ADCmin values showed a statistically significant difference between B3 lesions without and with malignancy or, for B3a lesions, atypia at DHE. They both showed a statistically significant difference also between B3a lesions without or with atypia or malignancy at DHE, but only $ADC_{min}$ (not $ADC_{mean}$) showed statistically significant difference between B3b lesions without or with malignancy at DHE. Conclusions: The ADC value could help distinguish between B3a lesions without or with atypia/malignancy at DHE after surgical excision and between B3b lesions without or with malignancy at DHE. Therefore, it could be used to help guide the diagnostic-therapeutic pathway of these lesions, particularly of B3a lesion

Prevalence and clinical outcome of hepatic haemangioma with specific reference to the risk of rupture: a large retrospective cross-sectional study.

BACKGROUND: Prevalence and incidence of hepatic haemangioma are estimated from autopsy series only. Although benign and generally asymptomatic, hepatic haemangioma can cause serious complications. AIMS: The aim of the study was to assess the prevalence of hepatic haemangioma and to attempt to quantify the risk of major complications such as spontaneous rupture. METHODS: We retrospectively analyzed the radiology database of a Regional University Hospital over a 7-year period: the radiological records of 83,181 patients who had an abdominal computed tomography or magnetic resonance scan were reviewed. Diagnoses made at imaging were reviewed and related to clinical course. RESULTS: Hepatic haemangioma was diagnosed in 2071 patients (2.5% prevalence). In 226 patients (10.9%), haemangioma had diameter of 4 cm or more (giant haemangioma). The risk of bleeding was assessed on patients without concomitant malignancies. Spontaneous bleeding occurred in 5/1067 patients (0.47%). All 5 patients had giant haemangioma: 4 had exophytic lesions and presented with haemoperitoneum; 1 with centrally located tumour experienced intrahepatic bleeding. CONCLUSION: Giant haemangiomas have a low but relevant risk of rupture (3.2% in this series), particularly when peripherally located and exophytic. Surgery might be considered in these cases

The Expanded Risk Score in Rheumatoid Arthritis: performance of a disease-specific calculator in comparison with the traditional prediction scores in the assessment of the 10-year risk of cardiovascular disease in patients with rheumatoid arthritis

The increased risk of cardiovascular disease has emerged as a major issue in patients with rheumatoid arthritis – it has been estimated that the cardiovascular disease burden in rheumatoid arthritis is comparable to that of diabetes mellitus

Magnetic Resonance Imaging (MRI)-Based Semi-Quantitative Methods for Rheumatoid Arthritis: From Scoring to Measurement

Rheumatoid arthritis (RA) is a chronic autoimmune disease that primarily affects the small joints of the hands and feet, characterized by pain, inflammation, and joint damage. In this context, magnetic resonance imaging (MRI) is useful to identify and monitor joint/tendon inflammation and the evolution of joint damage, playing a key role in treatment response evaluation, in addition to clinical measurements. Various methods to quantify joint inflammation and damage with MRI in RA have been developed, such as RA-MRI Score (RAMRIS), Early RA-MRI Score (ERAMRS), and Simplified RA-MRI Score (SAMIS). RAMRIS, introduced in 2002, offers an objective means to assess inflammation and damage via MRI in RA trials, encompassing findings such as synovitis, bone erosion, and edema/osteitis. Recently, an updated RAMRIS version was developed, which also includes the evaluation of joint space narrowing and tenosynovitis. The RAMRIS-5, which is a condensed RAMSIS version focusing on five hand joints only, has been proven to be a valuable resource for the semi-quantitative evaluation of RA joint damage, both in early and established disease. This narrative literature review will provide an overview of the MRI scoring systems that have been developed for the assessment of joint inflammation and structural damage in RA patients

Imaging of Sacroiliac Pain: The Current State-of-the-Art

Pain in the sacroiliac (SI) region is a common clinical manifestation, often caused by diseases involving the SI joints. This is typically due to inflammation or degenerative changes, while infections or cancer are less frequent causes. The SI joint is challenging to image accurately because of its distinct anatomical characteristics. For an accurate diagnosis, conventional radiography often needs to be supplemented with more precise methods such as magnetic resonance imaging (MRI) or computed tomography (CT). Sacroiliitis, a common presenting feature of axial spondyloarthritis (axial SpA), manifests as bone marrow edema, erosions, sclerosis, and joint space narrowing. Septic sacroiliitis and repetitive stress injuries in sports can also cause changes resembling inflammatory sacroiliitis. Other conditions, such as osteitis condensans ilii (OCI), can mimic the radiologic characteristics of sacroiliitis. Inflammatory lesions are diagnosed by concurrent erosions, hyperostosis, and ankylosis. Ligament ossifications or mechanical stress can also result in arthritic disorders. Determining the exact diagnosis can be aided by the distribution of the lesions. Inflammatory lesions can affect any part of the articulation, including the inferior and posterior portions. Mechanical lesions, such as those seen in OCI, often occur in the anterior middle region of the joint. In cases of idiopathic skeletal hyperostosis, ligament ossification is found at the joint borders. This pictorial essay describes common SI joint problems, illustrated with multimodal imaging data. We, also, discuss strategies for selecting the best imaging modalities, along with imaging pitfalls, key points, and approaches for treating patients with suspected inflammatory back pain

Experimental Paradigm for the Assessment of the Non-pharmacological Mechanism of Action in Medical Device Classification: The Example of Glycerine as Laxative

The evolution of medical devices has led to the introduction of medical devices that include “substances” and which, due to their presentation and sites of application may resemble medicinal products. The difference between substance-based medical devices and medicinal products lies in the proper definition of the principal mechanism of action. The major problem at the moment is the lack of a proper procedure for the demonstration of a mechanism that is “not pharmacological, immunological or metabolic.” We aimed to design an experimental set up to demonstrate the difference between the mechanism of action of two substances used commonly for the treatment of constipation, lubiprostone (example of medicinal product) and glycerine (example of medical device). By implementing cellular models and molecular analyses we demonstrate the difference in their mechanism of action. This set up can be considered an example on the possibility to define a paradigm for the case by case study of the mechanism of action of substances and combination of substances in medical devices