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Spatial and Temporal Distribution of Rainfall Breaks in Senegal

American Journal of Climate Change 2021年第4期10卷 533-560页

作者： Bara Ndiaye Mahamat Adoum Moussa Malick Wade Abdoulaye Sy Abdoulaye Bouya Diop Aichetou Dia Diop Bouya Diop Aboubakary Diakhaby laboratoire des sciences de l’atmosphère et de océans matériaux énergie dispositifs (lSAOMED) Saint-Louis Senegal

This study analyzes the spatio-temporal distribution of daily rainfall data from 13 stations in the country of Senegal located in the North-West of Africa. These data, covering the period 1950-2010, are extracted from the database of the regional Study Center for the Improvement of Drought Adaptation (CERAAS). They allow to calculate, in each station, dry episodes and their sequences and the results reveal a latitudinal variability of class 1 breaks (1 - 3 days) with the highest values recorded in the south. Unlike the class 2 episodes (greater or equal than 15 days), the latitudinal gradient is less pronounced but they are more frequent in the north. For most of the regions studied, a break in the trend towards an increase in dry sequences can be noted, most often at the beginning of the 1970s, which coincides with the start of the great drought of the 1970s decade. For all sites, the frequency of dry episodes of class 1 (1 - 3 days) exceeds 70%. The frequency of class 2 of dry episodes (greater or equal than 15 days) decreased from 30% in 1951-1970 to 18% in 1991-2010 in the region of Thiès;from 25% in 1951-1970 to 20% in 1991-2010 in louga;from 22% in 1951-1970 to 18% in 1991-2010 in Tamba;23% in 1951-1970 to 15% in 1991-2010 in Ziguinchor;25% in 1951-1970 to 16% in 1991-2010 in Kolda;22% in 1951-1970 to 18% in 1991-2010 in Diourbel and finally 20% in 1951-1970 to 17% in 1991-2010 in Fatick. Over the whole period of study, the spatial distribution of the number of dry periods in class 1 is higher in the South than in the Center and in the North of Senegal. For class 2 breaks, the latitudinal gradient is less pronounced and the minimum number of dry periods in this class is recorded in the south, especially in Ziguinchor. However, the maximum is observed in the Center. In the Northern region (Saint-louis), classes 3 and 4 are much more frequent. This spatial variability of rainfall breaks is clearly associated with the rainfall gradient between the North and the S

关键词： Rainfall Rainfall Breaks Great Drought Senegal Consecutive Dry Days

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Enhanced dielectric performance of Dy-substituted YMn2O5 for high-frequency applications

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Progress in Natural Science:materials International 2021年第5期31卷 762-771页

作者： H.Chouaibi K.Khirouni E.Dhahri laboratoire de Physique Appliquée Faculté des Sciences Université de Sfax laboratoire de Physique des matériaux et des Nanomatériaux Appliquée à l'Environnement Faculté des Sciences de Gabès Cité Erriadh Université de Gabès

The dielectric performances as well as the effects of Dy3+ions content at A sites of YMn2O5(YMO) [x=0(YDM0)and x=0.4(YDM0.4)] polycrystalline samples were *** compounds were synthesized via sol-gel method.X-Ray diffraction and Raman measurements proved the high quality of the compounds that crystallized in an orthorhombic structure with the Pbam space ***,impedance spectroscopy and electrical modulus studies revealed that both samples exhibited a non-debye’s type of *** decrease of impedance for YDM0.4compared to the pure YDM0,may be attributed to the decrease in charge transfer *** the fit of impedance spectra,they confirmed that both compounds were simultaneously capacitive and ***,the activation energies obtained from Modulus and complex impedance were proven to be neighboring,suggesting that the relaxation process refers to electron *** each compound,the evolution of ε’and tan & with temperature indicated a clearer relaxor behavior,namely the existence of two *** first one detected at low temperature is related to the charge carriers hopping between Mn3+and Mn4+and the second at high temperature is associated with oxygen *** reduced hopping rate with Dy3+substitution for Y3+ions at A sites is responsible for the decrease in dielectric constant and dielectric *** significant findings demonstrate that these materials can be invested in a fruitful use in UV photo-detector and power applications in high frequency as microwave,millimeter wave signal processing,for civilian,military and space applications.

关键词： Multiferroic relaxation phenomenon High dielectric constant relaxor behavior

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Performances Analysis of a System of localization by Angle of Arrival UWB Radio

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International Journal of Communications, Network and System sciences 2020年第2期13卷 15-27页

作者： Salick Diagne Thierry Val Abdou Karim Farota Bouya Diop Ognadon Assogba laboratoire des sciences de l’atmosphère et des océans: matériaux Energies et Dispositifs (LSAO-MED) Gaston Berger University Saint-Louis Senegal IRIT University of Toulouse2 Toulouse France

The increasingly widespread use of sensor and actuator networks and in general of the Internet of Things (IoT) in several areas of precision, imposes upon localization systems that can often equip them with a robust and more precise localization. It is in this sense that UWB technology has proved to be one of the most powerful communication technologies for these localization systems;thanks, in particular to the bandwidth occupied instantaneously by the signal allowing a very fine temporal resolution. Constructors have set up localization kits based on various technologies. These kits facilitate in a way the work of localization of users. In this paper, we present results on the performance study of the decawave PDoA Kit. This Kit uses the PDoA (Phase Difference of Arrival) to determine the Angle of Arrival (AoA) parameter with UWB technology. This study is in context of localization by AoA for an application to protect agricultural crops against grain-eating birds. The results of the study show overall AoA measurement errors around 10 degrees in an ideal environment.

关键词： Angle of Arrival (AoA) localization UWB PDoA

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Simulation of a Prototype 5G Network Integrating D2D Communication and MEC Technology

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Circuits and Systems 2023年第7期14卷 29-38页

作者： Abdou Karim Farota Harouna Moussa Sanghotte Salick Diagne Babacar Niang Bouya Diop laboratoire des sciences de l’atmosphère et de l’océan—matériaux Energie et Dispositifs Université Gaston Berger de Saint-Louis Saint-Louis Senegal

In this paper, we study the coexistence of two key technologies in the same fifth-generation network, namely D2D (device-to-device) communication and MEC (Multi-Access Edge Computing) technology. These two promising technologies each have important roles to play in future telecommunications networks. D2D communication is a technology that aims to improve communication efficiency, increase overall throughput, and decrease latency. Multi-Access Edge Computing, a promising new concept, overcomes the burden of core cloud servers. This makes it possible to provide large storage, compute, and resource capacities to mobile edge nodes. With its closest deployment to users, it significantly reduces end-to-end transmission time. Our architecture consists of an access network and a central network, a base station (gNodeB), users, an MEC server and a gateway (UPF) to connect it to the RAN (Radio Access Network) of the core network. The base station controls communication by managing signaling and interference. The MEC server is placed next to the BS to provide data to the devices. It plays the role of the cloud that is located in the core network and allows you to store data and then do calculations for good communication between devices. Finally, we did a simulation using the OMNet software. The results showed us that the data transmission passed well between the end devices, the antennas and the MEC server with very low latency and reliability.

关键词： D2D MEC Edge Computing Basic Station OMNet

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Study of the Spatio-Temporal Variability of Rainfall in the Northern region of Senegal

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Journal of Geoscience and Environment Protection 2023年第4期11卷 1-14页

作者： Aichétou Dia Diop Abdoul Karim Mbodji El Hadji deme Malick Wade Mahamat Adoum Moussa Abdoulaye Bouya Diop Younousse Biaye Djiby Sarr Abdou Karim Farota Aboubakary Diakhaby Bouya Diop laboratoire des sciences de l’atmosphère et des océans matériaux energies dispositifs UGB Saint Louis Senegal laboratoire D’études et de recherches en Statistiques et Développement University Gaston Berger (UGB) Saint Louis Senegal Ecole Nationale Supérieure des TIC N’Djamena Tchad

Senegal is a country of the Sahel. In this region, most of the populations live from agro-pastoral activities. The northern zone of Senegal is strongly influenced by river cultures. And the dynamics of the Senegal River are dependent on rainfall. The rainfall in the area is very closely linked to the dynamics of the atmosphere. The study of the spatio-temporal variability of rainfall in the northern region of Senegal requires quality rainfall observation data. It includes the Ferlo and the Senegal River valley, in particular the regions of louga (department of linguère included), Saint-louis (departments of Dagana and Podor included) and matam. These stations have been defined since le Borgne (1988). The difficulty of having quality rain observation data can be resolved by using more accessible and good quality satellite data. Using satellite data, namely MSWEP, CRU, TAMSAT, ARC and PERSIANN, we showed the return of precipitation that appeared in 2000 and the unimodal cycle of precipitation in our study area. These data were validated using the correlation coefficient, the bias, the RMSE and the Nash index with observation data from the regional Study Center for the Improvement of Adaptation to Drought (CERASS). The CRU data is then retained. Thus, this study made it possible to show the zonal distribution of rainfall in the northern zone of Senegal.

关键词： Rainfall in the Northern region of Senegal Variability of Rainfall Satellite Data The Zonal Distribution of Rainfall

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Electronic and magnetic structures of V-doped zinc blende Zn_(1-x)V_xN_yO_(1-y) and Zn_(1-x)V_xP_yO_(1-y)

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Chinese Physics B 2011年第8期20卷 419-424页

作者： N.Mamouni M.Belaiche A.Benyoussef A.El Kenz H.Ez-Zahraouy M.loulidi E.H.Saidi E.K.Hlil laboratoire de Magntisme et de Physique des Hautes energies Dpartement de Physique Associ au CNRSTURACB.P.1014Facult des SciencesRabatMorocco laboratoire de Magntisme Matriaux MagntiquesMicro-ondes et CramiqueENSRabatMorocco INANOTECH Institute of Nanomaterials and NanotechnologyMAScIRRabatMorocco laboratoire de Physique des Hautes energies Dpartement de Physique B.P.1014Facult des SciencesRabatMorocco Institut Nel MCMF-UJFC.N.R.SB.P.16638042 Grenoble CedexFrance

Electronic and magnetic structures of zinc blende ZnO doped with V impurities are studied by first-principles calculations based on the Korringa-Kohn-Rostoker （KKR） method combined with the coherent potential approximation （CPA）. Calculations for the substitution of O by N or P are performed and the magnetic moment is found to be sensitive to the N or P content. Furthermore, the system exhibits a half-metallic band structure accompanied by the broadening of vanadium bands. The mechanism responsible for ferromagnetism is also discussed and the stability of the ferromagnetic state compared with that of the paramagnetic state is systematically investigated by calculating the total energy difference between them by using supercell method.

关键词： ab initio calculations density of states magnetic moment doping diluted magneticsemiconductors

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An investigation of merging and diverging cars on a multi-lane road using a cellular automation model

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Chinese Physics B 2012年第11期21卷 565-572页

作者： K.Jetto H.Ez-Zahraouy A.Benyoussef laboratoire de Magnétisme et de la Physique des Hautes energies Universit'e Mohammed V Faculté des Sciences Ecole Hassania des Travaux Publics KM 7 Route DEL JADIDAB.P 8108OasisCasablancaMaroc

In this paper, we have investigated two observed situations in a multi-lane road. The first one concerns a fast merging vehicle. The second situation is related to the case of a fast vehicle leaving the fastest lane back into the slowest lane and targeting a specific way out. We are interested in the relaxation time T, i.e., which is the time that the merging （diverging） vehicle spends before reaching the desired lane. Using analytical treatment and numerical simulations for the NaSch model, we have found two states, namely, the free state in which the merging （diverging） vehicle reaches the desired lane, and the trapped state in which T diverges. We have established phase diagrams for several values of the braking probability. In the second situation, we have shown that diverging from the fast lane targeting a specific way out is not a simple task. Even if the diverging vehicle is in the free phase, two different states can be distinguished. One is the critical state, in which the diverging car can probably reach the desired way out. The other is the safe state, in which the diverging car can surely reach the desired way out. In order to be in the safe state, we have found that the driver of the diverging car must know the critical distance （below which the way out will be out of his reach） in each lane. Furthermore, this critical distance depends on the density of cars, and it follows an exponential law.

关键词： traffic flow merging and diverging area intelligent transportation system cellular au-tomation

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Trend and return level Analysis of Extreme Rainfalls in Senegal

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Journal of Water resource and Protection 2022年第3期14卷 221-237页

作者： Mamadou Sarr Mahamat Adoum Moussa El Hadji deme Bouya Diop laboratoire des sciences de l’atmosphère et des océans matériaux-energies-dispositifs (lSAOMED) Université Gaston Berger Saint-Louis Sénégal Ecole Nationale Supérieur des TIC (ENASTIC) N’Djamena Tchad laboratoire d’etudes et de recherches en Statistique et Développement (lERSTAD) Université Gaston Berger Saint-Louis Sénégal

In recent years, Senegal has been confronted with increasingly frequent and damaging extreme events. In the context of climate change, we conducted this study to characterize the trends of rainfall extremes in Senegal. In this work, we used daily rainfall data from 27 stations in Senegal from the period 1951 to 2005 (55 years). To study their linear trends, non-stationary extreme value models with time as a covariate are fitted to evaluate them. Our results indicate a decreasing trend of extreme rainfalls at most of the stations except for 5 stations. However, the decreasing trends are only significant for two stations (Thiès and Kidira), however, this can only be taken as information that climate change may have already impacted extreme rainfalls. For the 20-year and 30-year return periods, the results show that they have undergone changes, in fact for almost all stations, the trends in return periods are decreasing.

关键词： Climate Change Extreme Rainfall Rain Trend return level Senegal

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Monte Carlo study of nanowire magnetic properties

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Chinese Physics B 2013年第5期22卷 514-518页

作者： R. Masrour l. Bahmad A. Benyoussef laboratoire de Magnétisme et Physique des Hautes energies URAC 12Université Mohammed V-AgdalFaculté des Sciences laboratory of materials ProcessEnvironment and QualityCady Ayyad UniversityNational School of Applied Sciences

In this work, we use Monte Carlo simulations to study the magnetic properties of a nanowire system based on a honeycomb lattice, in the absence as well as in the presence of both an external magnetic field and crystal field. The system is formed with Nl layers having spins that can take the values σ= ± 1/2 and S =±1,0. The blocking temperature is deduced, for each spin configuration, depending on the crystal field A. The effect of the exchange interaction coupling Jp between the spin configurations σ and S is studied for different values of temperature at fixed crystal field. The established ground-state phase diagram, in the plane （Jp, △）, shows that the only stable configurations are：（1/2,0）, （1/2, ＋1）, and （1/2,- 1）. The thermal magnetization and susceptibility are investigated for the two spin configurations, in the absence as well as in the presence of a crystal field. Finally, we establish the hysteresis cycle for different temperature values, showing that there is almost no remaining magnetization in the absence of the external magnetic field, and that the studied system exhibits a super-paramagnetic behavior.

关键词： Monte Carlo simulations nanowire magnetic field crystal field

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D-term Chaotic Braneworld in Supergravity Constrained by WMAP9 Data

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Communications in Theoretical Physics 2014年第3期61卷 397-402页

作者： A.Safsafi M.Ferricha-Alami H.Chakir J.Inchaouh M.Bennai laboratoire de Physique de la matiére Condens'ee Equipe Physique Quantique et Applications Facultédes Sciences BenM’sik B.P. 7955 Université Hassan II-Mohammedia laboratoire de recherche Subatomique et Applications Facultédes Sciences Ben M’sik B.P. 7955 UniversitéHassanII-Mohammedia laboratoire de Physique de la matiére Condens'ee Equipe Physique Quantique et Applications Facultédes Sciences BenM’sik B.P. 7955 UniversitéHassan II-Mohammedia Groupement National de Physique des Hautes energies Focal Point LabUFR-PHE

We study a supergravity D-term chaotic inflationary model, in the context of the braneworld scenario, in particular we consider the Randal1-Sundrum model type 2. Using the latest release from the combination of WMAP9, eCMB, BAO, and Ho, we show that the inflation observables depend only on the number ore-folds N. We also derive all known spectrum inflationary parameters, which are widely consistent with WMAP9 data for a particular choice of values N specially for the scalar spectral index ns and the ratio r. However, the running of the scalar spectral index dns/dlnk is now excluded from the range given by the latest observational measurements.

关键词： D-term chaotic braneworld perturbation spectrum WMAP9

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