João Cardoso

Structural reliability analysis using Monte Carlo simulation and neural networks

This paper examines a methodology for computing the probability of structural failure by combining neural networks (NN) and Monte Carlo simulation (MCS). MCS is a powerful tool, simple to implement and capable of solving a broad range of reliability problems. However, its use for evaluation of very low probabilities of failure implies a great number of structural analyses, which can become excessively time consuming. The proposed methodology makes use of the capability of a NN to approximate a function for reproducing structural behavior, allowing the computation of performance measures at a much lower cost. This approach seems very attractive, and its main challenge lies in the ability of a NN to approximate accurately complex structural response. In order to assess the validity of this methodology, a test function and two structural examples are presented and discussed. The second example is also used to show how this methodology can be used to perform reliability-based structural optimization.

Numerical modeling of bone tissue adaptation—A hierarchical approach for bone apparent density and trabecular structure

In this work, a three-dimensional model for bone remodeling is presented, taking into account the hierarchical structure of bone. The process of bone tissue adaptation is mathematically described with respect to functional demands, both mechanical and biological, to obtain the bone apparent density distribution (at the macroscale) and the trabecular structure (at the microscale). At global scale bone is assumed as a continuum material characterized by equivalent (homogenized) mechanical properties. At local scale a periodic cellular material model approaches bone trabecular anisotropy as well as bone surface area density. For each scale there is a material distribution problem governed by density-based design variables which at the global level can be identified with bone relative density. In order to show the potential of the model, a three-dimensional example of the proximal femur illustrates the distribution of bone apparent density as well as microstructural designs characterizing both anisotropy and bone surface area density. The bone apparent density numerical results show a good agreement with Dual-energy X-ray Absorptiometry (DXA) exams. The material symmetry distributions obtained are comparable to real bone microstructures depending on the local stress field. Furthermore, the compact bone porosity is modeled giving a transversal isotropic behavior close to the experimental data. Since, some computed microstructures have no permeability one concludes that bone tissue arrangement is not a simple stiffness maximization issue but biological factors also play an important role.

A review of national guidelines for management of COPD in Europe

The quality of care can be improved by the development and implementation of evidence-based treatment guidelines. Different national guidelines for chronic obstructive pulmonary disease (COPD) exist in Europe and relevant differences may exist among them. This was an evaluation of COPD treatment guidelines published in Europe and Russia in the past 7 years. Each guideline was reviewed in detail and information about the most important aspects of patient diagnosis, risk stratification and pharmacotherapy was extracted following a standardised process. Guidelines were available from the Czech Republic, England and Wales, Finland, France, Germany, Italy, Poland, Portugal, Russia, Spain and Sweden. The treatment goals, criteria for COPD diagnosis, consideration of comorbidities in treatment selection and support for use of long-acting bronchodilators, were similar across treatment guidelines. There were differences in measures used for stratification of disease severity, consideration of patient phenotypes, criteria for the use of inhaled corticosteroids and recommendations for other medications (e.g. theophylline and mucolytics) in addition to bronchodilators. There is generally good agreement on treatment goals, criteria for diagnosis of COPD and use of long-acting bronchodilators as the cornerstone of treatment among guidelines for COPD management in Europe and Russia. However, there are differences in the definitions of patient subgroups and other recommended treatments. There are important differences between European national COPD guidelines http://ow.ly/U2P4y

Parallel computing techniques applied to the simultaneous design of structure and material

In this work a computational procedure for two-scale topology optimization problem using parallel computing techniques is developed. The goal is to obtain simultaneously the best structure and material, minimizing structural compliance. An algorithmic strategy is presented in a suitable way for parallelization. In terms of parallel computing facilities, an IBM Cluster 1350 is used comprising 70 computing nodes each with two dual core processors, for a total of 280 cores. Scalability studies are performed with mechanical structures of low/moderate dimensions. Finally the applicability of the proposed methodology is demonstrated solving a grand challenge problem that is the simulation of trabecular bone adaptation.

Chronic Obstructive Pulmonary Disease Guidelines in Europe: a Look Into the Future

Clinical practice guidelines are ubiquitous and are developed to provide recommendations for the management of many diseases, including chronic obstructive pulmonary disease. The development of these guidelines is burdensome, demanding a significant investment of time and money. In Europe, the majority of countries develop their own national guidelines, despite the potential for overlap or duplication of effort. A concerted effort and consolidation of resources between countries may alleviate the resource-intensity of maintaining individual national guidelines. Despite significant resource investment into the development and maintenance of clinical practice guidelines, their implementation is suboptimal. Effective strategies of guideline dissemination must be given more consideration, to ensure adequate implementation and improved patient care management in the future.

Use of CPAP to reduce arterial stiffness in moderate-to-severe obstructive sleep apnoea, without excessive daytime sleepiness (STIFFSLEEP): an observational cohort study protocol

Introduction Sleepiness is a cardinal symptom in obstructive sleep apnoea (OSA) but most patients have unspecific symptoms. Arterial stiffness, evaluated by pulse wave velocity (PWV), is related to atherosclerosis and cardiovascular (CV) risk. Arterial stiffness was reported to be higher in patients with OSA, improving after treatment with continuous positive airway pressure (CPAP). This study aims to assess whether the same effect occurs in patients with OSA and without sleepiness. Methods and analysis This observational study assesses the CV effect of CPAP therapy on a cohort of patients with moderate-to-severe OSA; the effect on the subcohorts of sleepy and non-sleepy patients will be compared. A systematic and consecutive sample of patients advised CPAP therapy will be recruited from a single outpatient sleep clinic (Centro Hospitalar de Lisboa Central—CHLC, Portugal). Eligible patients are male, younger than 65 years, with confirmed moderate-to-severe OSA and apnoea–hypopnea index (AHI) above 15/hour. Other sleep disorders, diabetes or any CV disease other than hypertension are exclusion criteria. Clinical evaluation at baseline includes Epworth Sleepiness Scale (ESS), and sleepiness is defined as ESS above 10. OSA will be confirmed by polygraphic study (cardiorespiratory, level 3). Participants are advised to undertake an assessment of carotid-femoral PWV (cf-PWV) and 24 hours evaluation of ambulatory blood pressure monitoring (ABPM), at baseline and after 4 months of CPAP therapy. Compliance and effectiveness of CPAP will be assessed. The main outcome is the variation of cf-PWV over time. Ethics and dissemination This protocol was approved by the Ethics Committees of CHLC (reference number 84/2012) and NOVA Medical School (number36/2014/CEFCM), Lisbon. Informed, written consent will be obtained. Its results will be presented at conferences and published in peer-reviewed journals. Trial registration number NCT02273089; Pre-results.

A three-dimensional hierarchical model for topology optimization of structures

The topology optimization of structures consists of the identification of solid and void regions within a design domain, for a given criterion and a prescribed amount of material. Using a material approach, the optimal topology is achieved by the distribution in space of a nonhomogeneous material of variable density. Regions with high density identify structure while regions with low value are interpreted as holes.

Ontology-Based Approach for Heterogeneity Analysis of EA Models

The different needs and domains of enterprises and how they employ EA modelling languages and tools can give rise to heterogeneity at the syntactical, structural and semantical levels. In particular, models dealing with the process perspective are becoming increasingly complex and hetereogeneous. This raises difficulties in managing and reusing EA models.

PRINCIPAL COMPONENT ANALYSIS OF DYNAMICAL DATA IN STRETCH SHORTENING CYLE OF HUMAN LOWER LIMB

Stretch Shortening Cycle (SSC) is a common element of the abilities and gestures of many occupational and sports, such as walking, running and jumping. The natural form of muscle function involves use of SSC muscle actions in which preactivated muscle is first stretched, eccentric action, and then followed by the shortening, concentric action [Carvalho, 2002]. On several different problems of biomechanics, as the study and characterization of a phenomenon mechanism, such as SSC, is given by a broad set of measures or variables, strongly correlated with each other, for which assessment, it is necessary to reduce dimensionality of the DataSet, while preserving maximum variability of original data. Comparison and evaluation of associated phenomena to SSC make it necessary the determination of the relationship between concerned variables. Several types of classifiers have been used to reduce dimensionality of the human locomotion data, in addition to the extraction of information about the movement pattern of an individual, a population or a phenomenon under study, namely in gait analysis [Vaughan, 1999], but not in SSC.

Prediction of severe exacerbations and mortality in COPD: the role of exacerbation history and inspiratory capacity/total lung capacity ratio

Background Severe exacerbations and mortality are major outcomes in COPD, and risk factors for these events are actively searched for. Several predictors of mortality have been identified in COPD. The inspiratory capacity/total lung capacity (IC/TLC) ratio has been shown to be a strong predictor of all cause and respiratory mortality in patients with COPD. The major objectives of this study were to analyze which clinical parameters, including lung volumes, were the best predictors of the 5-year cumulative risk of hospital admissions or death and the 5-year risk of exacerbations, in stable COPD patients. Methods This study retrospectively reviewed data from 98 stable COPD patients, consecutively recruited in 2012. Forced expiratory volume in 1 s (FEV1), modified Medical Research Council dyspnea scale, exacerbation history (ExH), Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2011 groups, and lung volumes were reviewed. Five years later, this population was evaluated for cumulative exacerbations, hospital admissions, and mortality. All the population, and GOLD group D separately, were analyzed. Results The cumulative 5-year combined risk of hospital admission or death was significantly predicted by the ExH and the IC/TLC ratio. Analyzing separately group D, FEV1 was the only predictor of this outcome. The frequency of exacerbations in the previous year was the best predictor of future cumulative 5-year risk of subsequent exacerbations, both for the total population and the GOLD D group. Conclusion ExH and IC/TLC ratio were the best predictors of the most severe outcomes in COPD (admissions or mortality), independently of COPD severity. FEV1 was the only predictor of the cumulative 5-year combined risk of hospital admission or death in the GOLD D group. ExH was the best predictor of 5-year cumulative future risk of exacerbations. Besides FEV1 and ExH, the IC/TLC ratio can be a useful predictor of severe outcomes in COPD.