# Robert TchitngaUniversité de Dschang · Department of Physics

Robert Tchitnga

PhD, HDR

## About

76

Publications

19,384

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846

Citations

Introduction

Additional affiliations

May 2018 - present

**Cameroon Physical Society**

Position

- CEO

## Publications

Publications (76)

Systems of oscillators whose internal phases and spatial dynamics are coupled, swarmalators, present diverse collective behaviors which in some cases lead to explosive synchronization in a finite population as a function of the coupling parameter between internal phases. Near the synchronization transition, the phase energy of the particles is repr...

Dynamics of bidirectionally coupled swarmalators subject to attractive and repulsive couplings is analyzed. The probability of two elements in different layers being connected strongly depends on a defined vision range rc which appears to lead both layers in different patterns while varying its values. Particularly, the interlayer static sync π has...

In the literature, hyperjerk systems raised up meaningful interest due to their simple and elegant structure as well as their complex dynamical features. In this work, we propose a novel 4D autonomous hyperjerk system which the particularity resides on the type of its nonlinearity namely the Van der Pol nonlinearity. The dynamics of this hyperjerk...

The present work studies a novel efficient compressed based cryptosystem which combines a dynamical parameter coming from high dimensional system, a dynamics S-box and a 2D compress sensing (2D-CS). Firstly, a secret key depending on input image is gotten via the SHA-256 function. That input image, decomposed into four sub-images uses chaotic seque...

A detailed study of the characteristics of the time-delay signature of a single loop optoelectronic oscillator incorporating a nonlinear amplifier of sine hyperbolic type is presented. We demonstrate that with appropriate values of the system parameters, the unique time-delay of the system cannot be traced in its dynamics. Such an advantage is expl...

The aim of our work is to characterize a mortar with a cement/"Ndoor" composite binder. We determine experimentally the mechanical properties of a mortar modified by partial substitution of cement by an addition called "Ndoor". In experimental campaign, we realize different formulations of mortar diversified by the dosage of cement and "Ndoor", whi...

Most of the simple Josephson junction (JJ) based circuits with chaotic behavior found in the literature are nonautonomous. Hyperchaotic JJ-based circuits are often either driven by an external force or result from coupling chaotic circuits. An autonomous simple circuit based on Josephson junction active element (JJ), with exactly three physical ene...

In this paper, bifurcation mechanism of bursting oscillations and function projective synchronization of the fractional order form for a memristive Lorenz based system are investigated. One of the key results is the dependance of relaxation time of bursting oscillation on the fractional order derivative. The newly proposed system has a line equilib...

Time-delayed dynamical systems generally feature smooth nonlinear transfer functions in the feedback loop, such as polynomial or sinusoidal functions. As a consequence, the complexity of their dynamical behavior mainly originates from the time-delay. In this paper, we explore the opposite case where the nonlinear transfer function is complex (
$cos...

We study the emergence of the traveling chimera state in a two-dimensional network of Hindmarsh-Rose burst neurons with the mutual presence of local and non-local couplings. We show that in the unique presence of the non-local chemical coupling modeled by a nonlinear function, the traveling chimera phenomenon occurs with a displacement in both dire...

The phenomenon of the chimera state symbolizes the coexistence of coherent and incoherent sections of a given population. This phenomenon identified in several physical and biological systems presents several variants, including the multichimera states and the traveling chimera state. Here, we numerically study the influence of a weak external elec...

In this paper, analytical and numerical studies of the influence of the long-range interaction parameter on the excitability threshold in a ring of FitzHugh-Nagumo (FHN) system are investigated. The long-range interaction is introduced to the network to model regulation of the Gap junctions or hemichannels activity at the connexins level, which pro...

This document presents the design of a prototype of a low-cost personal weather station suitable for farmers in rural areas who are or may not be engaged in rudimentary agriculture. This prototype measures several weather data: temperature, relative humidity, wind speed, wind direction, rainfall. For further data analysis, these are transmitted for...

This paper presents a novel fourth-order autonomous flux controlled memristive Wien-bridge system. Standard nonlinear diagnostic tools such as bifurcation diagram, graphs of largest Lyapunov exponent, Lyapunov stability diagram, phase space trajectory and isospike diagram are used to characterize dynamics of the system.
Results show that the system...

The objective of this study was to determine whether the kinetics of germination of seeds stimulated by multi-periodic and chaotic electromagnetic fields could be described using the modified Malthus-Verhulst equation. The electrical circuits used for magnetization could generate signals of period-1, -2, and -4 as well as chaotic ones. The study wa...

In the literature, existing Josephson junction based oscillators are mostly driven by external sources. Knowing the different limits of the external driven systems, we propose in this work a new autonomous one that exhibits the unusual and striking multiple phenomena among which coexist the multiple hidden attractors in self-reproducing process und...

This paper reports a new kind of mathematical model for language competition dynamics using compartmental epidemiological modeling approach. The model describes the competition between two languages, say the predominant one called language 1, and the less spoken language 2, both in the same community. We distinguish three groups of population build...

In this paper, we consider an array of FitzHugh-Nagumo (FHN) systems with R close neighbors. Each element (j) connects to another (m) and its 2R neighbors. Shifting these neighbors produces particular phenomena such as chimera and multi-chimera. Step traveling chimera is observed for a time dependent shift. Results show that, basing oneself on both...

A simple 5D hyperchaotic system recently introduced in the literature is modified by using a charge-controlled memristor model and striking behaviors are uncovered. The resulting system is a 6D hyperchaotic system, which generates hidden attractors with the unusual feature of having plan and line equilibrium under different parameter conditions. It...

In the framework of a project on simple circuits with unexpected high degrees of freedom, we report an autonomous microwave oscillator made of a CLC linear resonator of Colpitts type and a single general purpose operational amplifier (Op-Amp). The resonator is in a parallel coupling with the Op-Amp to build the necessary feedback loop of the oscill...

A simple driven bipolar junction transistor (BJT) based two-component circuit is presented, to be used as didactic tool by Lecturers, seeking to introduce some elements of complex dynamics to undergraduate and graduate students, using familiar electronic components to avoid the traditional black-box consideration of active elements. Although the ef...

Innovation, science and engineering are driving forces to mastering the global challenges of the next decades. The basis is education. ISEE stands for Innovation, Science, Engineering and Education. This book summarises the presentations, discussions and statements that were made during the ISEE-Africa conference held in Nairobi in 2019 from Januar...

This study aims to investigate the economic and environmental combination between building materials and fuel source to improve building energy performance by considering the entransy loss. The annual entransy losses through the residential building walls were determined using the degree-day’s method. Life cycle cost and life cycle assessment were...

We design and report an electrical circuit using a Josephson junction under periodic forcing that reveals extreme multistability. Its overall state equations surprisingly recall those of a well-known model of Josephson junction initially introduced in our circuit. The final circuit is characterized by the presence of two new and different current s...

This paper presents a 6D autonomous system, obtained by introducing a flux-controlled memristor model into an existing 5D hyperchaotic autonomous system. The dynamics of the novel system are investigated in terms of equilibrium points, bifurcation diagrams, Lyapunov exponent spectra, phase portraits, time series and attraction basins. Moreover, its...

This article describes an easy way to apply active control upon all jerk systems for which the linear part of the third-order differential jerk equation strongly depends on acceleration and velocity. The kernel of that methodology is to rewrite the jerk equation as a single implicit first-order differential equation escorted with a sliding variable...

This paper is investigating the hyperchaotic dynamics of a novel hyperchaotic oscillator (made of only three electronics components namely a transformer, a capacitor and a junction field ef- fect transistor (JFET)) obtained by modifying the simple chaotic circuit proposed by Tchitnga et al. (doi:10.1016/j.chaos.2011.12.017) and published within thi...

This paper is investigating the hyperchaotic dynamics of a novel hyperchaotic oscillator (made
of only three electronics components namely a transformer, a capacitor and a junction ﬁeld ef-
fect transistor (JFET)) obtained by modifying the simple chaotic circuit proposed by Tchitnga et al.
(doi:10.1016/j.chaos.2011.12.017) and published within this...

In this paper, we extend the sliding mode idea to a class of third order Jerk system derived from a single Op-Amp-based jerk circuit. This method is achieved by the introduction of a single first order sliding equation. First, we have overcome the generally observed chattering phenomenon that occurs when the sliding mode control (SMC) method is app...

p>This paper presents the Design and implementation into Field ProgrammableGate Array (FPGA) of a combine stream cipher and a simple linear congruential generator circuit to produce key stream. The LCG circuit is used to produce initialization vector (IV) each 2<sup>64</sup> clock cycle to the cipher trivium in other to strengthen the complexity of...

p>This paper presents the Design and implementation into Field ProgrammableGate Array (FPGA) of a combine stream cipher and a simple linear congruential generator circuit to produce key stream. The LCG circuit is used to produce initialization vector (IV) each 2<sup>64</sup> clock cycle to the cipher trivium in other to strengthen the complexity of...

In this paper, a fractional-order version of a chaotic circuit made
simply of two non idealized components operating at high frequency is presented. The
fractional-order version of the Hopf bifurcation is found when the bias voltage source and the fractional-order of the system increase.
Using Adams-Bashforth-Moulton predictor-corrector scheme, dyn...

We report the modeling for analysis of electrical clippers with side to side oscillating blade. The mathematical expressions for the study of its electromechanical dynamics are derived from the application of electromagnetics as well as mechanics laws. Numerical and analytical investigations reveal that, for well chosen range of its control paramet...

The relay coupling of three fractional-order two-stage oscillators in the presence of time delay has been explored theoretically, numerically and analogically. The global stabilization of the system in a finite time is proven through Hölder and Gronwall inequalities, as well as through inequality scaling skills. The Synchronization of the system is...

This paper exposes circuit design of linear congruential generator (LCG) and implementation in FPGA based on block reduction technique. The circuit is derived from LCG algorithm proposed by Lehmer. Block reduction technique has been used to simplify the circuit. Several net connections among the blocks of the circuit are ignored or disconnected and...

We study bifurcations and chaotic behavior of a periodically forced lever that is magnetically controlled. The system is extremely simple and low cost and can be assembled in a very short time. Both the theoretical simulations and the experimental measurements exhibit regions of periodic and chaotic behaviors, depending on the system parameters. Am...

Inductive devices with ferromagnetic core are widely used in many electronic circuits to store magnetic energy. They should be treated as nonlinear devices, and the nonlinearity of their characteristics arises from the dependence of inductance on current. Such inductors display saturation and hysteresis behaviors. In the present paper, we report a...

We show the existence and stability of frozen splay states as well as temporally chaotic splay states in
a coupled sine circle map lattice system using analytic and numerical techniques. The splay states are observed for
very low values of the nonlinearity parameter, i.e., for circle maps which deviate very slightly from the shift map
case. We also...

The paper is devoted to theoretical and experimental investigations of an electromechanical system consisting of DC motor, a physical pendulum with the repulsive magnets. The work consists of modeling, simulation and experimental measurements to validate the analytical predictions and the numerical simulation of the earlier introduced mathematical...

This paper addresses the problem of generalized finite-time function projective synchronization (GFFPS) of fractional-order chaotic systems. A modified fractional nonsingular terminal sliding mode surface and an appropriate robust fractional sliding mode control law are proposed, taking into account the effects of model uncertainties and of the ext...

A linear resistive-capacitive-inductance shunted junction (LRCLSJ) model obtained by replacing the nonlinear piecewise resistance of a nonlinear resistive-capacitive-inductance shunted junction (NRCLSJ) model by a linear resistance is analyzed in this paper. The LRCLSJ model has two or no equilibrium points depending on the dc bias current. For a s...

This study aims to investigate the influence of the combination of different types of fuel and building material on energy savings into buildings. The yearly cooling transmission loads of the building were determined using the degree-day’s concept. The optimization was based on a life cycle cost analysis. Five different fuels (fuel oil, hydroelectr...

The problem of finite-time synchronization of fractional-order simplest two-component chaotic
oscillators operating at high frequency and application to digital cryptography is addressed. After
the investigation of numerical chaotic behavior in the system, an adaptive feedback controller
is designed to achieve the finite-time synchronization of two...

This work is based on the comparative study of the thermal
behavior of earth block, cement block and stone buildings roofed
with corrugated iron sheet. For this purpose, heat equations for
these buildings were developed and the Gauss Seidel scheme was
used to solve them. The effects that the type of building materials
have on temperatures and the d...

We report a simple model of two drive-response-type coupled chaotic oscillators, where the response system copies the nonlinearity of the driver system. It leads to a coherent motion of the trajectories of the coupled systems that establishes a constant separating distance in time between the driver and the response attractors, and their distance d...

We report a simple model of two drive-response-type coupled chaotic oscillators, where the response system copies the nonlinearity of the driver system. It leads to a coherent motion of the trajectories of the coupled systems that establishes a constant separating distance in time between the driver and the response attractors, and their distance d...

In this paper we present a device able to send information on time and date into seven languages (the two official languages of Cameroon English, French and five national languages of Cameroon Medumba, Ghomala, Yemba, Meta, Kom) to an LCD screen through a VGA controller. Hardware architecture is implemented on an Altera EP2C8Q208C8N FPGA (Field Pro...

A novel modeling of general purpose operational ampli ers (Op-Amps) is made to approximate at best the
real model at high frequency. With this new modeling, it appears that certain oscillators usually studied under
ideal considerations or under many existing real models of Op-Amps have hidden subtle and attractive chaotic
dynamics hitherto unknown,...

In determining the properties and inductance of ferromagnetic core inductor, hysteresis modeling is of high importance. Many models are available to investigate those characteristics but they tend to be complex and difficult to implement. In this paper, we report a new mathematical model based on the experimental data of hysteresis for ferromagneti...

A low-cost phonocardiogram (PCG) is proposed to overcome some limitations known with the electrocardiograms (ECG). This small size portable PCG with a graphic LCD is equipped with a mini solar panel. It computes and displays different physical characteristics needed by physicians to ease cardiac auscultations, like the numerous heart beats per minu...

Background
The sensitivity of Optical Coherence Tomography (OCT) images to identify retinal tissue morphology characterized by early neural loss from normal healthy eyes is tested by calculating structural information and fractal dimension. OCT data from 74 healthy eyes and 43 eyes with type 1 diabetes mellitus with mild diabetic retinopathy (MDR)...

Firstly, the synchronization problem of the simplest two-component Hartley chaotic systems is considered. A simple and effective controller is used to achieve synchronization between the drive and response systems. The proposed controller is built around a linear and a nonlinear parts with each contributing to the achievement of the synchronization...

We numerically investigate the possibility of using a coupling to increase the complexity in simplest chaotic two-component electronic circuits operating at high frequency. We subsequently show that complex behaviors generated in such coupled systems, together with the post-processing are suitable for generating bit-streams which pass all the NIST...

In this paper, the dynamics and synchronization of a fractional-order four dimensional nonlinear system based on a twostage Colpitts oscillator is investigated, using the Grünwald-Letnikov method. The study of the fractional-order stability of the equilibrium states of the system is carried out. The bifurcation diagram confirms the occurrence of Ho...

The dynamics and robust finite-time hybrid projective synchronization of a fractional-order four-dimensional nonlinear system based on a two-stage Colpitts oscillator is investigated. The study of the fractional order stability of the equilibrium states of the system is carried out. The bifurcation diagram confirms the occurrence of Hopf bifurcatio...

This paper shows an experimental evidence of chaos in one of the simplest imaginable autonomous implicit Hartley’s oscillator made simply of a junction field effect transistor (JFET) and a tapped coil. The experimental setup is implemented. The variations of amplitude of the oscillations through the control element are obtained showing the domain o...

Existing devices for the management of electric storage modules in renewable energy power stations known as charge controllers are usually developed around the principle of controlling the voltage or current delivered by the generators for the charging of batteries. However, it is known that if the total power requested by 87 different receivers (l...

The sensitivity of OCT images to sample diabetic morphology is tested by calculating attenuation coefficients and fractal dimension. Fractal analysis provided a better sensitivity to early predict diabetic retinopathy.

The sensitivity of OCT images to sample diabetic morphology is tested by calculating attenuation coefficients and fractal dimension. Fractal analysis provided a better sensitivity to early predict diabetic retinopathy.

The photodissociation of small organic molecules, namely methyl iodide, methyl bromide, and methyl chloride, adsorbed on a metal surface was investigated in real time by means of femtosecond-laser pump-probe mass spectrometry. A weakly interacting gold surface was employed as substrate because the intact adsorption of the methyl halide molecules wa...

Being able to facilitate effective hands-on laboratory experiences in introductory physics courses is a challenging task, even when contemporary laboratory facilities, equipment, and new technologies for data collection and analysis are available. At institutions without adequate resources, especially those in developing countries, we have found th...

Nanosize gold clusters were grown by thermal evaporation on ultrathin magnesia films on Mo(100) and investigated by femtosecond (fs)-laser photoemission spectroscopy. The surface work function in this system was found to increase with increasing nominal gold coverage. Methyl bromide (CH3Br) molecules adsorb molecularly on the magnesia surface as we...