Search results for "Transient"
showing 10 items of 623 documents
Analysis of a Station Black-Out transient in SMR by using the TRACE and RELAP5 code
2014
The present paper deals with the investigation of the evolution and consequences of a Station Black-Out (SBO) initiating event transient in the SPES3 facility [1]. This facility is an integral simulator of a small modular reactor being built at the SIET laboratories, in the framework of the R&D program on nuclear fission funded by the Italian Ministry of Economic Development and led by ENEA. The SBO transient will be simulated by using the RELAP5 and TRACE nodalizations of the SPES3 facility. Moreover, the analysis will contribute to study the differences on the code predictions considering the different modelling approach with one and/or three-dimensional components and to compare the capa…
Measurement of ionization, charge exchange and ion confinement times in charge breeder ECR ion sources with short pulse 1+ injection of metal ions
2022
Abstract The Consecutive Transients (CT) method is used for estimating the characteristic times of ionization, charge exchange and confinement within the plasma of a Charge Breeder Electron Cyclotron Resonance Ion Source (CB-ECRIS). The method reveals differences in the characteristic times between different source configurations, with K9+ charge breeding efficiencies of 8.9 % and 20.4 %, and allows qualitative explanation of the improved breeding efficiency. The increase in K9+ efficiency is accompanied by a decrease in ionization time for low charge states, a decrease of charge exchange time for high charge states, and an overall decrease of the ion confinement time, which increases non-l…
One-Dimensional Transient Analysis of Rainfall Infiltration in Unsaturated Volcanic Ash
2015
The paper presents a one-dimensional hydro-mechanical analysis of rainfall infiltration in a loose volcanic ash and the utilisation of a factor of safety for the implementation of an early-warning system. Three different rainy seasons with different rainfall patterns were analysed . The analysis aims to understand the influence of the antecedent rainfall on the wetting front, the pore-water pressures and the factor of safety. The analysis was carried out in the context of a Master project of the first author at the Laboratory for Soil Mechanics of EPFL.
Inertial response of isolated power networks with wind power plants
2019
The constant increase of power generation provided by renewable energy source (RES) power plants is causing a progressive reduction of the overall inertia of the power systems. Especially in the case of small, isolated power networks, the replacement of conventional generation plants with RES power plants can affect significantly the frequency response of the system. The critical low-inertia conditions can be improved by the introduction of specific additional controls to the RES power converters. These control schemes are known as “synthetic inertia” or “virtual inertia” controls. The paper analyzes the impact of a derivative-based inertial control on a small, isolated power system, with a…
Experimental evaluation of hypertext access structures
2002
Transient hypertextual access structures (THASs) are temporary graphs formed automatically on the basis of the situation-dependent information needs of software engineers. The approach is implemented in the HyperSoft system, which is a hypertext-based software maintenance support tool. THASs highlight the relevant parts of the program and enable nonlinear browsing between them. The system also supports various graphical views whose elements are linked to the program text. This paper describes the effects of using these hypertextual structures in two separate experiments. The subjects of both experiments were computer science students (total N = 70). In both experiments, the subjects perform…
Approach to the analysis of nonlinear feedback oscillators under large-signal injection
1986
A method for the analysis of driven oscillators under high-level injection is presented. It applies to single-loop feedback systems with a memoryless nonlinear element and a second-order (high-Q) tank circuit. The analysis technique employed combines the classical block-diagram approach with an improved firstharmonic dynamic modelling to provide a couple of differential equations capable of accounting for the amplitude-dependence effects arising under large-signal operation. On this basis, first-and second-order approximate expressions are also derived, which allow a better understanding of the validity limits of previous theories on this subject. As an example of application, both the stea…
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…
Numerical study and comparisons with experimental data for transient behaviour of phase boundaries during industrial FZ process for silicon crystal g…
2005
Abstract In our numerical transient model developed previously for the industrial FZ crystal growth process with the needle-eye technique, the meshing algorithms are essentially improved and a significant amount of numerical studies are carried out for model verification. Transient modelling for the experimental growth process with step-like time dependences of inductor current and feed rod velocity has shown that time dependencies of the crystal radius and zone height calculated numerically agree with the data from praxis. The fully transient simulation for growth process of crystal starting cone has shown that the model is capable of performing the simulation even if the crystal diameter …
Parameter identification of linear induction motor model in extended range of operation by means of input-output data
2012
This paper proposes a technique for the off-line estimation of the electrical parameters of the equivalent circuit of linear induction machines (LIM), taking into consideration the end effects, and focuses on the application of an algorithm based on the minimization of a suitable cost function involving the differences of measured and computed by simulation inductor current components. This method exploits an entire start-up transient of the LIM to estimate all the 4 electrical parameters of the machine (Rs, L s, σ Ls, Tr). It proposes also a set of tests to be made to estimate the variation of the magnetic parameters of the LIM versus the magnetizing current as well as the magnetizing curv…
Transient Focal Neurological Events in Cerebral Amyloid Angiopathy and the Long-term Risk of Intracerebral Hemorrhage and Death: A Systematic Review …
2021
Importance Transient focal neurological episodes (TFNEs) are a frequently overlooked presentation of cerebral amyloid angiopathy (CAA), a condition with prognostic implications that are still not well described. Objective To perform a systematic review and meta-analysis to examine the factors associated with incident lobar intracerebral hemorrhage (ICH) and death in patients with CAA presenting with TFNEs. Data Sources A systematic review and individual participant meta-analysis including (1) a hospital-based cohort and (2) the results obtained from a systematic search performed in MEDLINE and Embase completed in December 2019. Study Selection Included studies were observational reports of …