The stiffness of laser stake welded T-joints in web-core sandwich structures

The purpose of this paper is to describe experiments carried out on laser stake welded T-joints of web-core steel sandwich structures. A special test setup was developed to measure the shear-induced rotation at the T-joint. The ratio of the shear force to rotation angle gave the joint stiffness. This stiffness was measured for specimens with two different face-plate thicknesses. The influence of weld thickness, root gap and occurrence of contact were further investigated with finite element simulations. Finally, the shear stiffness of the sandwich structure transverse to the web plate direction was determined using the experimentally obtained average joint stiffness value. The validation of the shear stiffness was carried out by considering a beam in four-point bending. The agreement between calculated deflection and stress and experimental results was found to be good.     

Kinetic parameters of the oxidation of zirconium alloys in simulated WWER water – Effect of KOH content

The pre-transition oxides formed on two different types of zirconium alloys (Zircaloy 4 and E110) have been characterised in situ using electrochemical impedance spectroscopy (EIS) in high-temperature electrolyte simulating WWER conditions at 310 °C. To obtain a correlation between the oxide film thickness, the oxide growth rate and the impedance parameters, the EIS data have been fitted to a transfer function derived from the mixed-conduction model for oxide films, allowing for the contribution of both an inner, barrier type of oxide and a more defective outer layer. The values of the total oxide film thickness based on the model calculations have proved to be in a good agreement with the values measured from the cross-section micrographs of the specimens using scanning electron microscopy. The main kinetic and transport parameters characterising the oxidation process have been estimated and discussed with regard to the effect of KOH content and alloy type on the mechanism of conduction through the formed oxide.     

Effect of Ceramic Particles on Properties of Cold-Sprayed Ni-20Cr+Al2O3 Coatings

Cold spraying is a thermal spray process enabling the production of metallic and metal-ceramic coatings with low porosity and low oxygen content, capable of, e.g., resisting corrosion. The aim of this study was to characterize the microstructural and mechanical properties of cold-sprayed Ni-20Cr+Al₂O₃ coatings and to clarify the effect of the hard particles on different coating properties. Accordingly, the research focused on the microstructure, denseness (impermeability), adhesion strength, and hardness of the coatings. Scanning electron microscopy (SEM) analysis and corrosion tests were run to gain information on the through-porosity. Ceramic addition in cold-sprayed Ni-20Cr+Al₂O₃ coatings improved their quality by lowering their porosity. Moreover, hardness was slightly higher than those of cold-sprayed Ni-20Cr coating, indicating a hardening effect by the ceramic particles. The addition of Al₂O₃ also made it possible to use high gas temperatures without nozzle clogging, which affects coating properties, such as coating thickness, denseness, and hardness.     

Pareto navigator for interactive nonlinear multiobjective optimization

We describe a new interactive learning-oriented method called Pareto navigator for nonlinear multiobjective optimization. In the method, first a polyhedral approximation of the Pareto optimal set is formed in the objective function space using a relatively small set of Pareto optimal solutions representing the Pareto optimal set. Then the decision maker can navigate around the polyhedral approximation and direct the search for promising regions where the most preferred solution could be located. In this way, the decision maker can learn about the interdependencies between the conflicting objectives and possibly adjust one’s preferences. Once an interesting region has been identified, the polyhedral approximation can be made more accurate in that region or the decision maker can ask for the closest counterpart in the actual Pareto optimal set. If desired, (s)he can continue with another interactive method from the solution obtained. Pareto navigator can be seen as a nonlinear extension of the linear Pareto race method. After the representative set of Pareto optimal solutions has been generated, Pareto navigator is computationally efficient because the computations are performed in the polyhedral approximation and for that reason function evaluations of the actual objective functions are not needed. Thus, the method is well suited especially for problems with computationally costly functions. Furthermore, thanks to the visualization technique used, the method is applicable also for problems with three or more objective functions, and in fact it is best suited for such problems. After introducing the method in more detail, we illustrate it and the underlying ideas with an example.     

Average power estimation under nonsinusoidal conditions

In this paper, the authors address the problem of estimating the average power of electrical systems under nonsinusoidal conditions. At first, a time-domain-based algorithm is proposed, which smoothes sampled data using suitable coefficients, prior to their numerical integration. Then, the algorithm accuracy is quantified with respect to wide-band noise. Last, simulation and experimental results are presented showing its effectiveness in estimating average power when starting from multifrequency voltage and current samples     

Wavelet packet modulation for wireless communications

As proven by the success of OFDM, multicarrier modulation has been recognized as an efficient solution for wireless communications. Waveform bases other than sine functions could similarly be used for multicarrier systems in order to provide an alternative to OFDM. In this paper, we study the performance of wavelet packet transform modulation (WPM) for transmission over wireless channels. This scheme is shown to be overall quite similar to OFDM but with some interesting additional features and improved characteristics. A detailed analysis of the system's implementation complexity as well as an evaluation of the influence of implementation‐related impairments are also reported. Copyright © 2004 John Wiley & Sons, Ltd.     

Indoor exposure to particulate matter and the incidence of acute lower respiratory infections among children: A birth cohort study in urban Bangladesh

Approximately half of all children under two years of age in Bangladesh suffer from an acute lower respiratory infection (ALRI) each year. Exposure to indoor biomass smoke has been consistently associated with an increased risk of ALRI in young children. Our aim was to estimate the effect of indoor exposure to particulate matter (PM_2.5) on the incidence of ALRI among children in a low‐income, urban community in Bangladesh. We followed 257 children through two years of age to determine their frequency of ALRI and measured the PM_2.5 concentrations in their sleeping space. Poisson regression was used to estimate the association between ALRI and the number of hours per day that PM_2.5 concentrations exceeded 100 μg/m³, adjusting for known confounders. Each hour that PM_2.5 concentrations exceeded 100 μg/m³ was associated with a 7% increase in incidence of ALRI among children aged 0–11 months (adjusted incidence rate ratio (IRR) 1.07, 95% CI 1.01–1.14), but not in children 12–23 months old (adjusted IRR 1.00, 95% CI 0.92–1.09). Results from this study suggest that reducing indoor PM_2.5 exposure could decrease the frequency of ALRI among infants, the children at highest risk of death from these infections.     

The transformative effect of top management governance choices on project team identity and relationship with the organization — An agency and stewardship approach

This study focuses on the relationship and identity changes within and between a project team and its organization following top management intervention in the context of a large international construction project. The study follows the project-as-practice orientation, examining the actions and behaviors of the project team through participant ethnography in the “praxis” of the project site over its entire duration. The longitudinal case allows the examination of the way the transition process established a new governance culture undermining the initial trust-based one and changed it from a virtual absence of mechanisms toward far more potent mechanisms of control, monitoring, and punishment. Simultaneously, the initial stewardship relationships and collectivist identity of the project team shifted toward agency relationships and individualistic identity. The triggers for the transformation process were identified as CEO succession, project failure, top management intervention driven changes in governance mechanisms, and perception of organizational betrayal of the project team.     

Remote Didactic Laboratory “G. Savastano,” The Italian Experience for E-Learning at the Technical Universities in the Field of Electrical and Electronic Measurements: Overview on Didactic Experiments

The Remote Didactic Laboratory Laboratorio Didattico Remoto - LA.DI.RE. ldquoG. Savastanordquo is the e-learning measurement laboratory supported by the Italian Ministry of Education and University. It involves about 20 Italian universities and provides students of electric and electronic measurement courses with access to remote measurement laboratories delivering different didactic activities related to measurement experiments. In order to demonstrate the versatility for didactic use, the overview of some experiments is given. The didactic experiments summarized in this paper concern measurement characterization of instruments and communication systems, measurement devices for remote laboratories, basic electrical measurements, magnetic measurements, electromagnetic-interference measurements, and signal processing for measurement applications.