Rayonnement parasite des terminaisons court-circuitées en ligne microfente et en guide d’onde coplanaire

An integral equations technique solved by the moment method associated with simple one-port model is used to analyse parasitic radiation of short circuit terminations of slotlines and coplanar waveguides. This parasitic effect is represented by a frequency-dependent normalized resistance. Theoretical results are compared to experimental ones for substrates with several dielectric constants.     

Mélangeur équilibré dans la bande de 26,5 à 40 GHz en technologie de la ligne à ailettes

The fin line technique has been used in a balanced 27.25–29.75 GHz mixer with a 3.75 GHz intermediate frequency. The performance of essential mixer circuits elements is presented. The mixer has an available conversion loss of 5.8 ± 0.8 dB. The mixer is tunable by variable shorts.     

Conception assistée par ordinateur de circuits millimétriques incluant des discontinuités de type ligne à ailettes

Single and complex fin line discontinuities are precisely computed by means of the modal analysis combined with the spectral domain approach. Validity of the results is established by measurements of the scattering parameters of symmetrical configurations including these discontinuities in a «back to back» arrangement. Frequency dependent equivalent networks are derived and they can be used as data base in circuit simulation programs.     

Optical properties of vanadium thin films

The optical constants of vanadium thin films of different thicknesses were determined in the spectral range of 2.5 to 8.5 m. These optical constants were used to evaluate some microcharacteristics of vanadium thin films such as the free charge concentration, the relaxation time, the static conductivity, the electron velocity at the Fermi surface, the mean free path and the specularity parameter.The determination of the microcharacteristics were carried out in conjunction with Drude's theory of free charge carriers as well as with anomalous skin effect theory.     

Next generation of low global warming potential refrigerants: Thermodynamic properties molecular modeling

The recent global agreement signed in Kigali to limit the use of hydrofluorocarbons (HFCs) as refrigerants, starting by 2019, has promoted an active area of research toward the development of low global warming potential (GWP) new refrigerants. Hydrofluoroolefins (HFOs) have been proposed as a low GWP alternative to third generation HFC refrigerants, but further work on fully characterizing them and their blends with other compounds is still required to fully assess their performance to replace the ones in current use. In this work, the polar and perturbed chain statistical associating fluid theory coupled with the density gradient theory is used to predict the vapor–liquid equilibrium, isobaric heat capacity, speed of sound, and surface tension of selected HFC and HFO‐based commercial azeotropic blends as fourth generation low GWP refrigerants, seeking for a predictive tool for these properties. © 2017 American Institute of Chemical Engineers AIChE J, 63: 250–262, 2018     

Transient performance analysis in robust nonlinear adaptive control

This paper deals with the problem of controlling unknown linear systems in the presence of strictly proper unmodelled dynamics and bounded disturbances. Adaptive controllers that ensure the closed-loop global (uniform) stability and asymptotic performances can be designed following either the backstepping approach or the certainty-equivalence method. The main shortcoming of the involved controllers is that they do not allow quantification of the closed-loop transient behaviour. In this paper, the transient issue is addressed for backstepping adaptive controllers. A L_∞ bound on the tracking error is explicitly given as a function of the design parameters. This shows that the error can be made arbitrarily small by sufficiently increasing the design gains.     

Control of Grid Connected Photovoltaic Systems with Microinverters: New Theoretical Design and Numerical Evaluation

This paper addresses the problem of controlling grid connected photovoltaic (PV) systems that are driven with microinverters. The systems to be controlled consist of a solar panel, a boost dc–dc converter, a DC link capacitor, a single‐phase full‐bridge inverter, a filter inductor, and an isolation transformer. We seek controllers that are able to simultaneously achieve four control objectives, namely: (i) asymptotic stability of the closed loop control system; (ii) maximum power point tracking (MPPT) of the PV module; (iii) tight regulation of the DC bus voltage; and (iv) unity power factor (PF) in the grid. To achieve these objectives, a new multiloop nonlinear controller is designed using the backstepping design technique. A key feature of the control design is that it relies on an averaged nonlinear system model accounting, on the one hand, for the nonlinear dynamics of the underlying boost converter and inverter and, on the other, for the nonlinear characteristic of the PV panel. To achieve the MPPT objective, a power optimizer is designed that computes online the optimal PV panel voltage used as a reference signal by the PV voltage regulator. It is formally shown that the proposed controller meets all the objectives. This theoretical result is confirmed by numerical simulation tests.     

Active fuzzy modeling for estimating problems in hydrocarbon reservoirs

While active learning method (ALM) uses error as the learning parameter, selection of the validation data is still challenging. In this paper, to prevent form encountering with sample size problem, we applied an error-independent version of ALM that we call the active fuzzy modeling (AFM) with a distance threshold to model parameters of hydrocarbon reservoirs. In this paper, we demonstrate that measuring the generalization error is a vital factor in the process of ALM. Regression (R) and mean squared error (MSE) for estimating RHOB by AFM were 0.96 and 0.0032, respectively. On the other hand, R of 0.91, 0.89 and 0.92 and MSE of 0.0051, 0.0067 and 0.0047 for ANN, TS-FIS and NF, respectively, illustrate that AFM performs much better in comparison with conventional modeling approaches and produces more reliable results. Comparing the results of the presented method with ANN, TS-FIS and NF in aspect of rapidity, robustness, storage, complexity and acceptability in estimating RHOB reports the accuracy and high-performance behavior of AFM. This method is illustrated by an example of an oil field at NW Persian Gulf.     

Nonlinear output feedback control of V2G single‐phase on‐board BEV charger

In this work, we consider the problem of controlling a single‐phase on‐board battery electric vehicle (BEV) charger with vehicle‐to‐grid (V2G) technology. The BEV charger consists of a bidirectional ac‐dc power converter connected to the single‐phase power grid, followed by a bidirectional dc‐dc power converter interfacing an EV battery pack. The main control objectives are fourfold: (i) Unitary Power Factor (UPF) in grid‐side; (ii) tight dc‐bus voltage regulation; (iii) safety battery charge and battery discharge during the grid‐to‐vehicle (G2V) mode and V2G mode, respectively; and (iv) asymptotic stability of the closed loop system. After an accurate system modelling, a nonlinear controller is designed using a backstepping design technique. The point is that the battery inner voltage is not accessible to measurement. Therefore, a nonlinear observer is invoked in order to estimate all non‐measured variables making the solution cheaper and noiseless. It is shown using a formal analysis and numerical simulations, that the proposed output feedback controller (combining a nonlinear controller and a nonlinear observer) meets all control objectives.