ABSTRACT
Linear variable differential transformer (LVDT) is a commonly used linear displacement sensor because of its good measurement characteristics. When using laminated ferromagnetic cores in LVDTs, it is very important to take eddy currents into the account during design phase of the sensor. Particularity of the open-type core means that the eddy currents induced by the stray magnetic flux that flow in large loops tangential to the lamination surfaces take on significant values. Due to the open-type core a typical LVDT has, depending on the core material, it is, therefore, very important to take eddy currents into the account when designing the sensor. This paper's goal is to present a methodology for calculating LVDT eddy current losses that can be applied to LVDT design in order to optimize the dimensions and help with selection of materials of the LVDTs, in order to achieve the highest measurement accuracy. Presented approach using an AτA-formulation with elimination of redundant degrees of freedom exhibits rapid convergence. In order to calculate the relationship between eddy current losses and core displacement, frequency, and material characteristics, a number of 3D finite element method (FEM) simulations was performed. Analysis of the obtained results using presented methodology for eddy current losses calculation in LVDTs enables the designer optimize the design of the LVDT.
ABSTRACT
With the aim of increasing the efficiency of maintenance and fuel usage in airplanes, structural health monitoring (SHM) of critical composite structures is increasingly expected and required. The optimized usage of this concept is subject of intensive work in the framework of the EU COST Action CA18203 "Optimising Design for Inspection" (ODIN). In this context, a thorough review of a broad range of energy harvesting (EH) technologies to be potentially used as power sources for the acoustic emission and guided wave propagation sensors of the considered SHM systems, as well as for the respective data elaboration and wireless communication modules, is provided in this work. EH devices based on the usage of kinetic energy, thermal gradients, solar radiation, airflow, and other viable energy sources, proposed so far in the literature, are thus described with a critical review of the respective specific power levels, of their potential placement on airplanes, as well as the consequently necessary power management architectures. The guidelines provided for the selection of the most appropriate EH and power management technologies create the preconditions to develop a new class of autonomous sensor nodes for the in-process, non-destructive SHM of airplane components.
ABSTRACT
INTRODUCTION: Hepatitis C virus (HCV) infection is one of the main causes of chronic liver disease worldwide. Pegylated interferon alfa-2a or 2b (PEG IFN alfa-2a or 2b) and ribavirin (RBV) represent a standard treatment of chronic hepatitis C (CHC). Sustained virological response (SVR), defined as continued undetectable HCV RNA 24 weeks after completion of treatment, is universally considered as an indicator of treatment efficacy. OBJECTIVE: The aim of this study was to determine efficacy and safety of PEG IFN alfa-2a and RBV treatment in patients with CHC in Serbia. METHODS: One hundred seventy-six patients with CHC were included in this multicenter trial from 8 reference centers in Serbia. The patients were treated with standard PEG IFN alfa-2a and RBV protocol. We performed the following virological testing: anti-HCV (ELISA), HCV RNK (quantitative PCR), HCV genotype (type-specific PCR), HBsAg, anti-HBs, anti-HBc and anti-HIV (ELISA). Histological activity and the degree of fibrosis were determined according to the Metavir scoring system. Potential predictors for achieving SVR were evaluated using multivariable logistic regression analysis. RESULTS: Of the treated patients with CHC 65.9% were male, and 60.2% of them aged over 40 years. Of the treated patients 68.2% had infection over 5 years, 63% had HCV RNA >400.000 IU/mL, 76.1% had HCV G1/4, and 60.1% had a mild to moderate liver fibrosis. SVR was achieved in 78.9% of patients (G1/4 79.1%; G2/3 78.1%). The factors that indicated a poorer efficacy of the treatment were age >40 (p<0.05), high basal viremia (p=0.013), and the reduction of PEG IFN alfa-2a and RBV doses, with interruption of therapy (p<0.001). Of the treated patients 45.9% had adverse affects (G1/4 50.8%; G2/3 29.7%). CONCLUSION: Treatment of CHC with PEG IFN alfa-2a and RBV was efficient in 78.9% of patients. The safety profile of therapy was satisfactory. Longer therapy increases the possibility of the development of adverse affects. No life-threatening adverse effects were recorded in our patients.
