Search results for "STIFFNESS"

Effect of steel collars on the seismic behaviour of axially-cracked historical stone columns

2014

Granite and heavy stone circular columns could often be found in the cultural heritage among ancient churches and historical buildings in all the Mediterranean area. Their good strength properties allow them to carry big load values, while their bright colours and aesthetical characteristics were used by a lot of architects in the past to achieve structural solutions with great visual impact.Though such materials have great compressive strength values, environmental effects, especially long term effects, can damage the structural members, by cracking them. In this way the slenderness of the column increases, and the presence of an imposed ground motion can be very dangerous, since the colum…

INFLUENCE OF HIV INFECTION AND ANTIRETROVIRAL THERAPY ON AORTIC STIFFNESS: A META-ANALYSIS.

2018

INTRODUCTION: A growing body of evidence indicates that risk of CV events is higher in HIV-infected patients (HIV?) when compared to HIV-uninfected persons (HIV-). This enhanced risk may in part be mediated through preclinical CV damage. Large artery stiffness, a well-documented marker of arterial damage and predictor of adverse CV prognosis, is usually assessed by measuring aortic pulse wave velocity (PWV). Several studies examined arterial stiffness in HIV? with inconsistent results. In a previous meta-analysis, showing increased arterial stiffness in HIV? than in HIV- subjects, studies assessing aortic and peripheral PWV were pooled together. This may be misleading, because only the form…

INFLUENCE OF HIV INFECTION AND ANTIRETROVIRAL THERAPY ON AORTIC STIFFNESS

2018

Objective: A growing body of evidence indicates that risk of CV events is higher in HIV-infected patients (HIV+) when compared to HIV-uninfected persons (HIV-). This enhanced risk may in part be mediated through preclinical CV damage. Large artery stiffness, a well-documented marker of arterial damage and predictor of adverse CV prognosis, is usually assessed by measuring aortic pulse wave velocity (PWV). Several studies examined arterial stiffness in HIV+ with inconsistent results. In a previous meta-analysis, showing increased arterial stiffness in HIV+ than in HIV- subjects, studies assessing aortic and peripheral PWV were pooled together. This may be misleading, because only the former …

A machine learning approach to determine airport asphalt concrete layer moduli using heavy weight deflectometer data

2021

An integrated approach based on machine learning and data augmentation techniques has been developed in order to predict the stiffness modulus of the asphalt concrete layer of an airport runway, from data acquired with a heavy weight deflectometer (HWD). The predictive model relies on a shallow neural network (SNN) trained with the results of a backcalculation, by means of a data augmentation method and can produce estimations of the stiffness modulus even at runway points not yet sampled. The Bayesian regularization algorithm was used for training of the feedforward backpropagation SNN, and a k-fold cross-validation procedure was implemented for a fair performance evaluation. The testing p…

On the Energy Efficiency of Dual Prime Mover Pump-Controlled Hydraulic Cylinders

2019

Abstract This paper concerns the energy efficiency of a special class of pump-controlled hydraulic cylinders utilizing two prime movers. The performance of such circuits has been studied previously motivated by their capability of providing an actuator stiffness similar to that of servo valve-controlled systems. This characteristic may improve performance and robustness in applications requiring feedback control. In this paper, the presence of losses similar to that of fluid throttling, in the sense that they occur even in the absence of component inefficiencies, are demonstrated for such circuits and shown to degrade the overall energy efficiency of the system. The conditions under which s…

RELATIONSHIP BETWEEN OXIDATIVE STRESS AND AORTIC STIFFNESS IN HYPERTENSIVE PATIENTS WITH CHRONIC KIDNEY DISEASE

2011

Methods for Experimentally Determining Stiffness of a Multi-Axis Machining Centre

2019

This paper deals with global methods for experimentally determining the static stiffness of multi-axis machining centres. Different devices used for measuring deflection, in specific, are explored, where accuracy and usability are highlighted. The methods were tested on a 3-axis CNC milling machine, 2-axis trunnion table and a 6-DOF industrial robot.

Method for estimating combined controller, joint and link stiffnesses of an industrial robot

2014

In this paper a new combined local/global approach for estimating the combined stiffnesses of joints in anthropomorphic robots is presented. The stiffness of each joint is a combination of several effects: i) stiffness of the links, ii) stiffness of joint bearings and gears and iii) stiffness of the position control loops given by the individual axis controller gains in the controller software. Experimental results are presented for an ABB IRB6600 industrial robot using measurements from a FARO Xi laser tracker and an ATI Omega160 force/torque sensor. The results show that there is a significant variation in stiffness among the individual joints of the robot and that the stiffnesses of the …

The metabolic syndrome-arterial stiffness relationship in patients with ischaemic stroke: role of inflammation

2008

THE INFLUENCE OF TOOL STIFFNESS OF THE LIFETIME OF THE INSERTS IN INTERRUPTED CUTTING OPERATIONS

1989

ABSTRACT In the present paper the influence exerted by the stiffness of the tool-workpiece system under working conditions on tool life up to the fracture of carbide inserts in interrupted cutting is investigated. It is shown how, with the increase in compliance of the system, there is a corresponding increase in the average tool life of the insert which is greater the lesser the cutting speed. The results of tests carried out indicate as a possible cause the amount of damage evident in the successive phase of tool engagement with the workpiece. It was observed how, in this phase, the tool, vibrating at the same rate as the toolholder produces alternations in the cutting force. This effect …