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Thermophysical Characterization of Local Materials from a Locality in Chad for Use in Eco-Building

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Open Journal of Civil Engineering 2024年第3期14卷 486-497页

作者： Abderahman Adoum Oumar Malloum Soultan Abdallah Dadi Togdjim Jonas Mahamat Saleh Abdel-Khadir mahamoud youssouf khayal Salif Gaye Laboratoire de Recherche en Energtique et Matriaux (LREM) de lINSTA Institut National Suprieur des Sciences et Techniques dAbch Abch Chad Ecole Doctorale Science Technique et Environnement Universit de NDjamena NDjamena Tchad Laboratoire CABET (Construction Alternative Basse Energie au Tchad) NDjamena Chad Laboratoire de Matriaux dnergtique dlectricit et dconomie (LM3E) Universit Iba Der Thiam de This This Sngal

With the aim of enhancing the value of local building materials, the subject of this paper is a thermophysical study of natural Chadian clay from the eastern region of Chad, “Abeche”. Samples were taken from a brickwork in Abeche from a depth of 1 m, then using a clay brick-making press, 4 × 5 × 8 cm3 clay test tubes were made with 2%, 4%, 6% and 8% cow dung, and a 100% clay sample was used as a control. These samples underwent thermophysical characterization using the hot-wire method with a hot-plane option, yielding results that could improve thermophysical performance. The thermal conductivity of the test sample is in the order of 0.715 to 0.420 W/m. K, at 8% for cow dung, so the addition of cow dung as a percentage in the clay matrix enabled us to obtain various satisfactory thermal parameters.

关键词： Soils Characterization Thermophysical Local Building

Beamforming Scheme for MIMO Relay Based 5G and beyond Wireless Network

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Open Journal of Applied Sciences 2021年第10期11卷 1157-1176页

作者： Ali mahamoud Ali Bakhit Amine Adoum Idriss Saleh Bachar mahamoud youssouf khayal Laboratoire de Mathématiques Modélisation Informatique Applications et Simulation LARTIC FSEA/école Doctorale Sciences Techniques et Environnement CNRD Université de N’Djamena N’Djamena Tchad Ecole Nationale Superieure des Technologies de l’Information et de la Communication (ENASTIC) N’Djamena Tchad

In this paper, in order to attain the maximum ergodic capacity and significantly increase the spectral efficiency of wireless communication systems, novel linear beamforming is proposed for dual-hop amplify-and-forward (AF) multi-relay networks. The linear beamforming is designed based on the maximization of the signal-to-interference-plus-noise ratio (SINR) and signal-to- leakage-and-noise ratio (SLNR). The channel state information (CSI) is used in applying this new design to multi-relay (MR) nodes between the source and relays as well as relays and destination. The beamforming optimization problem is solved by using the Fukunaga-Koontz Transform (FKT). The scheme can achieve intra-node array and distributed gains by using multiple antennas and multi-relays (MRs). The performance of the proposed scheme demonstrates that by considering interference mitigation criteria the ergodic capacity at a significant level is improved as compared to the conventional techniques. Therefore, the proposed techniques based on the maximization of the signal-to-interference-plus-noise ratio (SINR) and signal-to-leakage-and-noise ratio (SLNR) relay processing outperform other conventional techniques in case of a multi-relay dual-hop network in terms of ergodic.

关键词： Beamforming Ergodic Capacity MIMO Multi-Relay Network

A Novel Bow-Tie Antenna with Triple Band-Notched Characteristics for UWB Applications

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Journal of Electromagnetic Analysis and Applications 2016年第12期8卷 271-282页

作者： Abdoulaye Chaibo Assane Ngom mahamoud youssouf khayal Kharouna Talla Aboubaker Chedikh Beye Groupe de Laboratoires de Physique des Solides et Science des Matériaux (GLPSSM) Département de Physique Université Cheikh Anta Diop de Dakar Sénégal Département des Télécommunications et Multimédia (DTM) Institut National Supérieur des Sciences et Techniques d’Abéché Tchad Université Cô te d’Azur CNRS LEAT Sophia Antipolis France Centre National de Recherche pour le Développement (CNRD) N’Djamena Tchad

This paper presents the design of a compact bow-tie antenna with triple band notched characteristics for UWB applications. The proposed antenna can operate from 3.1 to 10.6 GHz with VSWR - 8.4 GHz) centered at 8.1 GHz, the CSRR2 rejects the WLAN band (5.15 - 5.85 GHz) centered at 5.6 GHz, and the CSRR3 rejects the band (4.10 - 4.47 GHz) centered at 4.32 GHz. Compared with recent design, this antenna is more compact, and presents better simulation results of its characteristics. Our newly designed antenna is a potential candidate for application in UWB communication systems.

关键词： Bow-Tie Antenna Ultra Wide Band (UWB) Antenna CSRRs Notch Band

A Comprehensive Survey of Candidate Waveforms for 5G, beyond 5G and 6G Wireless Communication Systems

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Open Journal of Applied Sciences 2023年第1期13卷 136-161页

作者： Bakhit Amine Adoum Kalsouabe Zoukalne Mahamat Saleh Idriss Ali Mahmoud Ali Amir Moungache mahamoud youssouf khayal Ecole Nationale Superieure des Technologies de l’Information et de la Communication (ENASTIC) N’Djamena Tchad Institute of Sciences and Techniques of Abeche (INSTA) Abeche Tchad Université de N’Djamena N’Djamena Tchad Virtual University of Chad N’djamena Tchad Centre National de Recherche pour le Developpement (CNRD) N’djamena Tchad

The evolution of global mobile data over the past decades in broadcasting, Internet of Things (IoT), education, healthcare, commerce, and energy has put strong pressure on 3G/4G mobile networks to improve their service offerings. These generations of mobile networks were initially invented to meet the requirements of the above-mentioned applications. However, as the requirements in these applications continue to increase, new mobile technologies such as 5G (fifth generation), 5G and beyond (B5G, beyond fifth generation), and 6G (sixth generation) are still progressing and being experimented. These networks are very heterogeneous generations of mobile networks that will have to offer very high throughput per user, good energy efficiency, better traffic capacity per area, improved spectral efficiency, very low latency, and high mobility. To meet these requirements, the radio interface of future mobile networks will have to be flexible and rationalized the available frequency resources. Therefore, new modulation methods, access techniques and waveforms capable of supporting these technological changes are proposed. This review presents brief descriptions of the types of 5G, B5G, and 6G waveforms. The 5G consists of OFDM including its transmission techniques: generalized frequency division multiplexing (GFDM), filter bank based multi-carrier (FBMC), universal filtered multi-carrier (UFMC), and index modulation (IM). Meanwhile, the 6G covers orthogonal time frequency space (OTFS), orthogonal chirp division multiplexing (OCDM) and orthogonal time sequence multiplexing (OTSM). The networks’ potentialities, advantages, disadvantages, and future directions are outlined.

关键词： Modulation 5G B5G 6G Waveforms

Influence of Climate Temperature on the Valorization of Dung-Wastewater Slaughterhouse Biogas in Two Regions: In Chad and Senegal

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Natural Resources 2019年第4期10卷 81-95页

作者： Haroun Ali Adannou Saka Goni Mahamat Bichara Abderaman mahamoud youssouf khayal Ache Abouya Khamis Moulaye Aidara Talla Kharouna Aboubaker Chedich Beye Department of Physics Faculty of Science and Technology/Cheikh Anta Diop University of Dakar Dakar Senegal Department of Chemical Engineering National Institute of Petroleum of Mao Mao Chad Department of Industrial Engineering and Maintenance Polytechnic University of Mongo Mongo Chad Virtual University of Chad N’Djamena Chad Panafrican Institute for Online Education Dakar Senegal

In this work, we have produced biogas by co-digestion of cow dung and slaughterhouse wastewater under different climate temperatures in two countries: N’Djamena in Chad, a country of Central Africa and Dakar in Senegal, a country of West Africa. In a first approach, we put the cow dung in cans of 1.5 L, hermetically closed. The goal was to know how long you could produce biogas. Then we built a bio-digester to produce biogas for cooking. Each bio-digester was exposed to receive solar heat that varied between 27°C to 41°C in Chad and between 24°C to 30°C in Senegal. Influenced by the high temperature and a minimum residence time, the experiments showed that the N’Djamena test produced biogas more quickly than the Dakar test which, on the contrary, had a low temperature and a long residence time. The production of biogas began at the end of seven days with flammability on the twenty-first day for the bio-digester in Chad and after twenty-seven days with a flammability on the thirty-sixth day for the bio-digester of Senegal. The different digestates were valorised in fertilizers, bricks and green coal. Our research aims to meet the living conditions of the rural world specifically for women by reducing their work and thus allowing them to have more time to self-educate and educate their children.

关键词： Co-Digestion Climate Temperature Cow Dung Slaughterhouse Wastewater Biogas Digestat Rural World Self-Education

Numerical Study of Natural Convection in a Porous Square Enclosure with Sinusoidally Varying Temperature Profile on the Bottom Wall

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Open Journal of Fluid Dynamics 2017年第3期7卷 263-275页

作者： Alhadj Hisseine Issaka Ali Samba Dia mahamoud Y. khayal Cheikh Mbow Aboubaker Chedikh Beye Department of Physics Cheikh Anta University Diop of Dakar Dakar Senegal Department of Hydrocarbons Exploitation Higher National Petroleum Institute of Mao Mao Chad Department of Technical Sciences University of N’Djamena N’Djamena Chad

This current study focuses on the simulation of natural convection in square cavity filled with a porous medium considered homogenous, isotropic and saturated by a Newtonian fluid obeying the law of Darcy and the hypothesis of Boussinesq. The lower horizontal wall of the enclosure is subjected to a temperature varying sinusoidally with the space while the upper horizontal wall is maintained adiabatic. The vertical walls are kept cold isotherm. In order to generalize the results, all governing equations are put into dimensionless form, discretized by the Finite Difference Method and solved by the relaxed Gauss Seidel (SUR) Algorithm. A code has been proposed in Fortran 95, in order to solve numerically the equations of the problem. The study parameters are the Rayleigh-Darcy number (Ra) and the amplitude (Ar) of the hot wall temperature. The effects of the Rayleigh-Darcy number and amplitude on the dynamic and thermal field, the horizontal velocity distribution and the mean horizontal temperature distribution (y = 0.5) were presented and discussed. It emerges from this study that the increases of the amplitude and Rayleigh-Darcy number intensify the flow and the global transfer of heat in our physical domain.

关键词： Natural Convection Porous Media Numerical Method Sinusoidal Temperature