Search results for "transient"

A new phase locked loop strategy for power quality instruments synchronisation

2006

Power quality instrumentation requires the accurate fundamental frequency estimation and the signal synchronization, even in presence of disturbances. In the paper the authors present an innovative synchronization technique, based on a single phase software PLL. To evaluate how the synchronization technique is adversely affected by the application of stationary and transient disturbing influences, appropriate testing conditions have been developed, taking into account the requirements of the in-force standards. In the paper the proposed technique is described and PLL performances in presence of stationary and transient disturbances are presented

Implementation of active infrared NDT techniques using long square heating pulses

2012

The present work describes the implementation of active IR Thermography techniques for the NDT of thick polymer and glass-fibre reinforced polymer (GRP) composite panels. A low cost Thermal NDT set-up is proposed, comprising a single-detector IR camera with low thermal resolution and low frame rate, and common low-power halogen lamps as external heat source devices. The use of halogen lamps in particular requires several seconds of switch-on time in order to deliver meaningful and effective heat quantities. The influence of such long heat deposition intervals is investigated on the possibility to implement Transient Thermography and Lock-In Thermography techniques. Regarding the Transient T…

Computational issues of an electromagnetics transient meshless method

2019

In this paper we refer to the computational issues in solving Maxwell’ s curl equations without using any connectivity among the points in which the problem domain is discretized. The adopted procedure is able to approximate the electric and magnetic vector fields making use of the derivatives of a kernel function at points arranged in the computational domain. In order to improve the numerical accuracy, dealing with irregular data distribution or data located near the boundary, a suitable strategy is considered. The computational core of the overall process requires elementary linear algebra operations. In the paper the method is presented and the discussion is revolved to the computationa…

Discovery of the optical counterpart to the CGRO transient GRO J1008 - 57

1994

Zur Diagnostik der transitorischen Osteoporose der Hüfte und deren Darstellbarkeit in der MR-Tomographie

2008

Magnetic resonance (MR) imaging may distinguish transient osteoporosis of the hip from more severe hip diseases. 12 patients with transient osteoporosis of the hip underwent MR imaging. The initial and follow-up studies included T1- and T2-weighted images in coronal, transverse or sagittal planes. There were revealed 3 stages: diffuse-, focal-, and residual stage. This syndrome is characterized by hip pain, limping, and osteoporosis of the femoral head with preservation of the joint space. The clinical symptoms and abnormalities on MR images disappeared completely within 6-10 months.

A Very Large Area Telescope for γ-Ray Astronomy Above 100 MeV Employing Limited Streamer Tubes

1994

A new detector for γ-ray astronomy above 100 MeV is described in which the electron-positron pairs are tracked by means of a set of plane arrays of Limited Streamer Tubes. This technique allows to build up very large area experiments which are specifically useful to study variable or transient sources.

Numerical study of emission and dynamics from a TDE-powered jet

2012

A transient event Swift J1644+57 is thought to be caused by the emission from a collimated relativistic jet. The jet, powered by the sudden onset of accretion onto a supermassive black hole following the tidal disruption of a star, collides with the gaseous circumnuclear medium and produces forward and reverse shocks which emit synchrotron radiation. We perform 1D and 2D relativistic hydrodynamic simulations using the MRGENESIS code. The aim of the simulations is to study the dynamics of a jet thought to exist in transient events such as Swift J1644+57, as discussed in recent literature. We discuss 1D and 2D jet evolution, on-axis radio light curves and differences between 1D and 2D jet dyn…

THE POTENTIALS OF A TRANSIENT TRANSNATIONAL COMMUNITY FOR TEACHER EDUCATORS’ PROFESSIONAL LEARNING AND DEVELOPMENT

2020

Although there has been a rising interest in the profession of teacher educators, there is still a lack of research looking at the professional learning and development of teacher educators. Taking a European perspective, we intend to contribute to the field of teacher education. At the outset we outline current literature and research findings, indicating various challenges that teacher education professionals face in today’s society, which are prominent in many contexts of language teacher education. Choosing to study a transient transnational community of 11 teacher educators as an autoethnographic case, we draw on qualitative data collected in the context of the ERASMUS+ project proPIC …

3D Data Acquisition and Numerical Analysis of a Footwear in Walking

2004

The aim of the paper is to set a procedure to study the load history of a footwear during a step with non-linear FE analysis. The geometric model tested was reconstructed from a real shoe by means of Reverse Engineering process, starting from dense point clouds acquired by non-contact scanning system. For each phase of the walk, the pressure values are obtained by a pressure distribution platform when tester is walking along the platform. The Finite Element model is easily generated by Hypermesh software using the CAD model. Ansys software is used to perform non-linear analyses. The procedure can be employed for improving the product performance in terms of durability, flexibility and comfo…

Analysis of bias-shift effects in free-running and injection-locked negative resistance oscillators

2012

In this paper, the interaction between DC and RF in quasi-sinusoidal free-running and injection-locked oscillators is addressed. To account for and illustrate in a user-friendly manner the bias-shift related effects stemming from such interaction, a frequency-domain method of analysis has been developed for a rather wide class of negative-resistance circuits. Grounding on a first-approximation exact perturbation-refined approach, it permits computationally efficient simulation of the oscillator behavior directly in terms of the DC and RF signals evolutions (dynamical complex envelopes). In fact, it allows the investigation of both steady-state and transient operation of the shifting-bias dr…