GROUPS HAVING MANY 2-GENERATED SUBGROUPS IN A GIVEN CLASS

Gherbi, Fares,Trabelsi, Nadir Korean Mathematical Society 2019 대한수학회보 Vol.56 No.2

If 𝖃 is a class of groups, denote by F𝖃 the class of groups G such that for every $x{\in}G$, there exists a normal subgroup of finite index H(x) such that ${\langle}x,h{\rangle}{\in}$ 𝖃 for every $h{\in}H(x)$. In this paper, we consider the class F𝖃, when 𝖃 is the class of nilpotent-by-finite, finite-by-nilpotent and periodic-by-nilpotent groups. We will prove that for the above classes 𝖃 we have that a finitely generated hyper-(Abelian-by-finite) group in F𝖃 belongs to 𝖃. As a consequence of these results, we prove that when the nilpotency class of the subgroups (or quotients) of the subgroups ${\langle}x,h{\rangle}$ are bounded by a given positive integer k, then the nilpotency class of the corresponding subgroup (or quotient) of G is bounded by a positive integer c depending only on k.

Groups having many 2-generated subgroups in a given class

Fares Gherbi,Nadir Trabelsi 대한수학회 2019 대한수학회보 Vol.56 No.2

If $\mathfrak{X}$ is a class of groups, denote by F$\mathfrak{X}$ the class of groups $G$ such that for every $x\in G$, there exists a normal subgroup of finite index $H(x)$ such that $\left\langle x,h\right\rangle \in\mathfrak{X}$ for every $h\in H(x)$. In this paper, we consider the class F$\mathfrak{X}$, when $\mathfrak{X}$ is the class of nilpotent-by-finite, finite-by-nilpotent and periodic-by-nilpotent groups. We will prove that for the above classes $\mathfrak{X}$ we have that a finitely generated hyper-(Abelian-by-finite) group in F$\mathfrak{X}$ belongs to $\mathfrak{X}$. As a consequence of these results, we prove that when the nilpotency class of the subgroups (or quotients) of the subgroups $\left\langle x,h\right\rangle$ are bounded by a given positive integer $k$, then the nilpotency class of the corresponding subgroup (or quotient) of $G$ is bounded by a positive integer $c$ depending only on $k$.

Techno-Economic Optimization of a Grid-Connected Hybrid Energy System Considering Voltage Fluctuation

Saib, Samia,Gherbi, Ahmed,Kaabeche, Abdelhamid,Bayindir, Ramazan The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.2

This paper proposes an optimization approach of a grid-connected photovoltaic and wind hybrid energy system including energy storage considering voltage fluctuation in the electricity grid. A techno-economic analysis is carried out in order to minimize the size of hybrid system by considering the benefit-cost. Lithium-ion battery type is used for both managing the electricity selling to the grid and reducing voltage fluctuation. A new technique is developed to limit the voltage perturbation caused by the solar irradiance and the wind speed through determining the state-of-charge of battery for every hour of a day. Improved particle swarm optimization (PSO) methods, referred to as FC-VACPSO which combines Fast Convergence Particle Swarm Optimization (FCPSO) method and Variable Acceleration Coefficient Based Particle Swarm Optimization (VACPSO) method are used to solve the optimization problem. A comparative study has been performed between standard PSO method and PSO based methods to extract the best size with the benefit cost. A sensitivity analysis has been studied for different kinds and costs of batteries, by considering variable and constant state-ofcharge of battery. The simulations, performed under Matlab environment, yield good results using the FC-VACPSO method regarding the convergence and the benefit cost of the hybrid system.

Efficient Implementation of the MQTT Protocol for Embedded Systems

Deschambault, Olivier,Gherbi, Abdelouahed,Legare, Christian Korea Information Processing Society 2017 Journal of information processing systems Vol.13 No.1

The need for embedded devices to be able to exchange information with each other and with data centers is essential for the advent of the Internet of Things (IoT). Several existing communication protocols are designed for small devices including the message-queue telemetry transport (MQTT) protocol or the constrained application protocol (CoAP). However, most of the existing implementations are convenient for computers or smart phones but do not consider the strict constraints and limitations with regard resource usage, portability and configuration. In this paper, we report on an industrial research and development project which focuses on the design, implementation, testing and deployment of a MQTT module. The goal of this project is to develop this module for platforms having minimal RAM, flash code memory and processing power. This software module should be fully compliant with the MQTT protocol specification, portable, and inter-operable with other software stacks. In this paper, we present our approach based on abstraction layers to the design of the MQTT module and we discuss the compliance of the implementation with the requirements set including the MISRA static analysis requirements.

Techno-Economic Optimization of a Grid-Connected Hybrid Energy System Considering Voltage Fluctuation

Samia Saib,Ahmed Gherbi,Abdelhamid Kaabeche,Ramazan Bayindir 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.2

This paper proposes an optimization approach of a grid-connected photovoltaic and wind hybrid energy system including energy storage considering voltage fluctuation in the electricity grid. A techno-economic analysis is carried out in order to minimize the size of hybrid system by considering the benefit-cost. Lithium-ion battery type is used for both managing the electricity selling to the grid and reducing voltage fluctuation. A new technique is developed to limit the voltage perturbation caused by the solar irradiance and the wind speed through determining the state-of-charge of battery for every hour of a day. Improved particle swarm optimization (PSO) methods, referred to as FCVACPSO which combines Fast Convergence Particle Swarm Optimization (FCPSO) method and Variable Acceleration Coefficient Based Particle Swarm Optimization (VACPSO) method are used to solve the optimization problem. A comparative study has been performed between standard PSO method and PSO based methods to extract the best size with the benefit cost. A sensitivity analysis has been studied for different kinds and costs of batteries, by considering variable and constant state-ofcharge of battery. The simulations, performed under Matlab environment, yield good results using the FC-VACPSO method regarding the convergence and the benefit cost of the hybrid system.

Efficient Implementation of the MQTT Protocol for Embedded Systems

( Olivier Deschambault ),( Abdelouahed Gherbi ),( Christian Legare ) 한국정보처리학회 2017 Journal of information processing systems Vol.13 No.1

The need for embedded devices to be able to exchange information with each other and with data centers is essential for the advent of the Internet of Things (IoT). Several existing communication protocols are designed for small devices including the message-queue telemetry transport (MQTT) protocol or the constrained application protocol (CoAP). However, most of the existing implementations are convenient for computers or smart phones but do not consider the strict constraints and limitations with regard resource usage, portability and configuration. In this paper, we report on an industrial research and development project which focuses on the design, implementation, testing and deployment of a MQTT module. The goal of this project is to develop this module for platforms having minimal RAM, flash code memory and processing power. This software module should be fully compliant with the MQTT protocol specification, portable, and inter-operable with other software stacks. In this paper, we present our approach based on abstraction layers to the design of the MQTT module and we discuss the compliance of the implementation with the requirements set including the MISRA static analysis requirements.