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Alireza Karimi

Cette personne a quitté l’EPFL

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Publications associées (163)

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Electronic origin of the isostructural decomposition in cubic M1-xAlxN (M=Ti, Cr, Sc, Hf): A first-principles study

Alireza Karimi

We have used first-principles calculations to investigate the mixing enthalpies, lattice parameters and electronic density of states of the ternary nitride systems Ti1-xAlxN, Cr1-xAlxN, Sc1-xAlxN and Hf1-xAlxN in the cubic B1 structure where the transition ...

2008

Formation of cubic structured (Al1-xCrx)(2+delta)O-3 and its dynamic transition to corundum phase during cathodic arc evaporation

Alireza Karimi, Hossein Najafi

Mixed aluminum-chromium oxide coatings in the form of (Al,Cr)(2)O-3 solid solutions have attracted extensive research interest during the past years due to their successful use for challenging wear applications and the comparative ease of their moderate-te ...

Elsevier Science Sa2013

Texture change through film thickness and off-axis accommodation of (002) planes

Alireza Karimi, Ayat Karimi, Akshath Raghu Shetty

We present our recent experimental results on the formation of off-axis texture and crystallographic tilting of crystallites that take place in thin film of transition metal nitrides. For this purpose, the microstructural development of TiAlN film was stud ...

2011

Robust Loop Shaping Controller Design for Spectral Models by Quadratic Programming

Alireza Karimi, Roland Longchamp, Gorka Galdos Sanz de Galdeano

A quadratic programming approach is proposed to tune fixed-order linearly parameterized controllers for stable LTI plants represented by spectral models. The method is based on the shaping of the open-loop or closed-loop frequency functions in the Nyquist ...

2007

Robust Controller Design by Linear Programming with Application to a Double-Axis Positioning System

Alireza Karimi, Roland Longchamp, Marc Kunze

A linear programming approach is proposed to tune fixed-order linearly parameterized controllers for stable LTI plants. The method is based on the shaping of the open-loop transfer function in the Nyquist diagram. A lower bound on the crossover frequency a ...

2007

Data-driven tuning of linear parameter varying precompensators

Alireza Karimi

Methods for direct data-driven tuning of the parameters of precompensators for LPV systems are developed. Since the commutativity property is not always satisfied for LPV systems, previously proposed methods for LTI systems that use this property cannot be ...

Wiley-Blackwell2010

Fixed-structure H-2 controller design for polytopic systems via LMIs

Alireza Karimi

In this paper a new approach for fixed-structure H2 controller design in terms of solutions to a set of linear matrix inequalities are given. Both discrete- and continuous-time single-input single-output (SISO) time- invariant systems are considered. Then ...

Wiley-Blackwell2015

Robust Controller Design For Linear Systems With Nonlinear Distortions: A Data-Driven Approach

Alireza Karimi, Achille Nicoletti

The extensive use of frequency-domain tools for analyzing and controlling linear systems have become indispensable for the control systems engineer. However, due to the increased performance demands on today's industrial systems, the effects of certain non ...

Elsevier2018

Structural and mechanical properties of Nb-1 (-) xTixN thin films deposited by rf magnetron sputtering

Alireza Karimi, Ayat Karimi, Daniela Dumitriu La Grange

Nb1-xTixNy thin films with different nitrogen contents (0.5 < y < 1.2) and Nb/Ti ratios (0

Elsevier2016

Data-driven distributed frequency/voltage and power sharing control for islanded microgrids

Alireza Karimi, Dongdong Zheng

In this paper, a new data-driven distributed control structure for frequency/voltage regulation and active/reactive power sharing of islanded microgrids is proposed. By using a droop-free concept, the proposed method avoids the inherent timescale separatio ...

2020

Frequency-domain data-driven position-dependent controller synthesis for Cartesian Robots

Alireza Karimi, Philippe Louis Schuchert

Cartesian robots have position-dependent dynamics that should be accounted for in high performance applications. Traditional methods design Linear Time Invariant (LTI) controllers which are robustly stable with respect to position variations, but require a ...

2023

Plug-and-play Voltage Stabilization in Inverter-interfaced Microgrids via a Robust Control Strategy

Alireza Karimi

This paper proposes a decentralized control strategy for the voltage regulation of islanded inverter-interfaced micro- grids. We show that an inverter-interfaced microgrid under plug- and-play (PnP) functionality of distributed generations (DGs) can be cas ...

Institute of Electrical and Electronics Engineers2017

Data-Driven Robust Passivity-Based Controller Design for Grid-Connected Converters

Alireza Karimi, Seyed Sohail Madani

Due to the integration of renewable-based Distributed Generation Units (DGUs), Energy Storage Systems (ESSs) and electric car charging stations, more and more power electronic converters are connected to the grid. In grids with a high penetration rate of t ...

2023

Influence of oxygen content on structure and properties of multi-element AlCrSiON oxynitride thin films

Alireza Karimi

Multi-element oxynitrides of type Al-Cr-Si-O-N were prepared using r.f. magnetron sputtering from Al80Cr2.5Si17.5 (at.%) target composition and O-2/(O-2+N-2) gas flow ratio between 0 and 100%. Two series of samples varying from pure nitrides to pure oxides ...

2010

Linear Parameter-Varying Control of A Power-Synchronized Grid-Following Inverter

Alireza Karimi, Behrooz Bahrani

This paper proposes a Linear Parameter-Varying loop-shaping controller for a power-synchronized grid-following inverter (PSGFLI). This control strategy regulates the inverter output active and reactive power at the terminal instead of the point of connecti ...

2022

Correlation between anionic substitution and structural properties in AlCr(OxN1-x) coatings deposited by lateral rotating cathode arc PVD

Alireza Karimi, Hossein Najafi

The influence of oxygen content on the properties of cathodic arc-deposited AlCr(OxN1-x) coatings has been studied. All samples were prepared in a nitrogen-rich mixture of N-2 and O-2 at 550 degrees C using lateral rotating arc cathodes (LARC) technology t ...

2011

Decoupled dq-Current Control of Grid-Tied Voltage Source Converters Using Nonparametric Models

Alfred Rufer, Alireza Karimi, Behrooz Bahrani

This paper presents a vector control strategy for regulating the current of grid-tied voltage source converters (VSCs) in a rotating reference frame. The proposed approach is based on shaping the open-loop and closed-loop transfer matrices of the system. S ...

Institute of Electrical and Electronics Engineers2013

Microstructure of Al95.5Cr2.5Si2(N1-xOx) thin films covering from nitrides to oxides

Alireza Karimi, Hossein Najafi

Al95.5Cr2.5Si2(N1-xOx) thin films were prepared using pulsed DC-magnetron sputtering at 650 degrees C by changing the oxygen to nitrogen ratio (O-2/(O-2 + N-2)) in the reactive gas. The obtained films were characterized by various techniques including XRD, ...

2011

Multivariable Control of Single-Inductor Dual-Output Buck Converters

Alfred Rufer, Alireza Karimi, Behrooz Bahrani

Cross regulation is the main technical drawback of a Single-Inductor Multiple-Output (SIMO) dc-dc converter. This paper proposes a multivariable digital controller to suppress the cross regulation of a Single-Inductor Dual-Output (SIDO) buck converter in C ...

Ieee2013

A comparison of model-based and data-driven controller tuning

Alireza Karimi

In many industrial applications, finding a model from physical laws that is both simple and reliable for control design is a hard and time-consuming undertaking. When a set of input/output measurements is available, one can derive the controller directly f ...

Wiley-Blackwell2014