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Pavel F.,Technical University of Civil Engineering Bucharest
Soil Dynamics and Earthquake Engineering | Year: 2015

This short article evaluates the stochastic method of ground motion simulation for Bucharest area using both the single-corner frequency model and recently introduced double-corner frequency models. A dedicated Q model is derived using ground motions obtained during the largest Vrancea earthquakes from the past 30 years. The simulated ground motions are tested against the observed data from the Vrancea earthquakes of August 1986 and May 1990. Moreover, the observed data are also compared against simulations obtained using the Q model derived by Oth et al. (2008). Finally, the results of the simulations show that the derived Q model is better suited for larger magnitude events, while the Q model of Oth et al. (2008) provides better results for smaller earthquakes. © 2014 Elsevier Ltd. Source

Nastase I.,Technical University of Civil Engineering Bucharest | Meslem A.,University of La Rochelle
Experiments in Fluids | Year: 2010

Passive control of jet flows in order to enhance mixing and entrainment is of wide applicative interest. Our purpose is to develop new air diffusers for HVAC systems, by using lobed geometry nozzles, in order to ameliorate users the thermal comfort. Two turbulent 6-lobed air jets with and without lobe deflection angles were studied experimentally and compared with a reference circular jet having the same initial Reynolds number. The main objective was to analyze the modifications occurring in the vortex dynamics of the flow, firstly by replacing a circular tube with a straight lobed tube, and secondly by a lobed tube having a double inclination of the lobes. Rapid visualizations of the flows and hot-wire measurements of the streamwise velocity spectra allow understanding the vortex roll-up mechanisms. Unlike the circular jet, where the primary rings are continuous, the Kelvin-Helmholtz vortices in the lobed jet flows were found to be discontinuous. The resulting "ring segments" detach at different frequencies whether they are shed in the lobe troughs or at the lobe sides. One explanation relies on the strong variation of the exit plane curvature. Additionally, a speculative scenario of the vortical dynamics is advanced by the authors. The discontinuous nature of the K-H vortices enables the development of secondary streamwise structures, non-influenced by the passage of the primary structures as in the case of the circular jet. Thus, the momentum flux transport role played by the streamwise structures is rendered more efficient and leads to a spectacular increase in the entrainment rate in the initial region. The amount of fluid being entrained in the lobed jet by the streamwise structures is drastically amplified by the double inclination of the nozzle exit boundary. © 2009 Springer-Verlag. Source

Barbulescu A.,Technical University of Civil Engineering Bucharest
Water Resources Management | Year: 2016

In this article we propose a new method - the Most Probable Precipitation Method (MPPM) - for estimating the precipitation at regional scale. Comparisons with the Thiessen polygons methods (TPM), inverse distance weighting interpolation (IDW) and ordinary kriging (OK) on annual, monthly, seasonal and annual maximum monthly precipitation are provided. In all cases MPPM performs better than IDW and OK, and in most of them, better than TPM. © 2015, Springer Science+Business Media Dordrecht. Source

Popescu D.,Technical University of Civil Engineering Bucharest
WSEAS Transactions on Systems | Year: 2014

The article makes an analysis of the functioning for the heating automation system with hot air blown into an individual dwelling. The structure of the automatic control system for indoor temperature in the dwelling is determined, in which the controller is a thermostat having feature type relay with hysteresis, the conditions related to the evolution of automatic control of the process are specified and the oscillation period of the control system is calculated. The automatic temperature control system model in individual dwelling is established using Simulink and its functioning by simulation in different representative situations is checked. The results of the simulation are compared with those obtained by calculation or they are used to determine the performance of the automatic control system. Source

Catalina T.,Technical University of Civil Engineering Bucharest | Iordache V.,Technical University of Civil Engineering Bucharest
Building and Environment | Year: 2012

Nowadays, the indoor environment quality (IEQ) is growing as a new and very useful index of the building quality. The current literature presents the IEQ assessment based on questionnaires applied for existing building. The original approach of this study consists in the development of an IEQ index model that can be used by architects and engineers during design stage, in order to use it as an evaluation indicator or optimize the building energy consumption versus indoor environmental conditions. Based on a large database of values resulted from simulations, multiple non-linear regression models were obtained in order to predict variables such as operative temperature, indoor sound pressure level, indoor average illuminance and specific energy consumption. A predictive model for IEQ index is proposed as a function of the four quality indexes (air quality, thermal, acoustic and visual comfort). The entire approach was tested by means of a study case where the impact of windows' size and type on the IEQ assessment is discussed for a random climate. Also, there are presented detailed results concerning the monthly variation of IEQ and its correlation with the energy consumption. The proposed method proves to be a fast and useful method to verify architectural and engineering solutions according to the IEQ estimator. © 2011 Elsevier Ltd. Source

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