Articles et Chaps publiés en externe

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Réduction du bruit de deux avions commerciaux en approche par une technique de commande optimale
(Researchgate, 2010) Nahayo, Fulgence; Khardi, Salah; Hamadiche, Mahmoud; Et al.
L’objectif de ce travail est le d´eveloppement d’un mod`ele d’optimisation acoustique de trajectoires de vol minimisant les bruits per¸cus au sol pour deux avions. Il s’agit de minimiser le bruit tenant compte des contraintes de vol. La dynamique de vol, associ´ee au crit`ere `a minimiser g´en`ere un probl`eme de commande optimale r´egi par des ´equations diff´erentielles ordiniaires non-lin´eaires. Le probl`eme est resolu `a l’aide d’une m´ethode newtonienne consid´erant les conditions d’optimalit´e de Karush-Kuhn-Tucker et une m´ethode SQP. Les r´esultats obtenus montrent des r´eductions significatives des niveaux de bruit. En fonction de la distance s´eparant les deux avions en vol, la trajectoire optimale d’approche est obtenue.
The Trust Region Sequential Quadratic Programming method applied to twoaircraft acoustic optimal control problem
(Researchage, 2011) Khardi, Salah; Nahayo, Fulgence; Haddou, Mounir
This paper aims to reduce noise levels of two-aircraft landing simultaneously on approach. Constraints related to stability, performance and ight safety are taken into account. The problem of optimal control is described and solved by a Sequential Quadratic Programming numerical method 'SQP' when globalized by the trust region method. By using a merit function, a sequential quadratic programming method associated with global trust regions bypasses the non-convex problem. This method used a nonlinear interior point trust region optimization solver under AMPL. Among several possible solutions, it is shown that there is an optimal trajectory leading to a reduction of noise levels on approach.
Two-Aircraft Dynamic System on Approach. Flight Path and Noise Optimization
(Applied Mathematical Sciences, 2012) Nahayo, F.; Khardi, S.; Haddou, M.
The aim of this paper is to present and to solve a mathematical model of two-aircraft optimal control problem reducing noise during the approach. This is a non-convex optimal control problem governed by ordinary non-linear differential equations. A Symplectic Partitioned Runge-Kutta discretization and the Pontryaguin maximum principle are used. Discretization scheme provides a sufficiently high order requiring a computation of the partial derivatives of the aircraft dynamic parameters. The nonlinear interior point trust region optimization solver is applied. Numerical experiments and results are presented. They confirm the feasible optimized trajectories contributing to a significant noise reduction.
Two-Aircraft optimal control problem. The in-flight noise reduction
(ResearchGate, 2012) Nahayo, Fulgence; Khardi, Salah; Haddou,Mounir; Et al.
The aim of this paper is to present and solve a mathematical model of a two-aircraft optimal control problem reducing the noise on the ground during the approach. The mathematical modelization of this problem is a non-convex optimal control governed by ordinary non-linear differential equations. To solve this problem, A direct method and a Runge-Kutta RK4 discretization schema are used. This discretization schema is chosed because it is a sufficiently high order and it does-not require computation of the partial derivatives of the aircraft dynamic. The Nonlinear Interior point Trust Region Optimization solver KNITRO is applied. A large set of numerical experiments is presented. The obtained results give feasible trajectories with a significant noise reduction.
Two-Aircraft Dynamic System on Approach. Flight Path and noise Optimization
(ResearchGate, 2012) Nahayo, Fulgence; Khardi, Salah; Haddou, Mounir
The aim of this paper is to present and to solve a mathematical model of two-aircraft optimal control problem reducing noise during the approach. This is a non-convex optimal control problem governed by ordinary non-linear differential equations. A Symplectic Partitioned Runge-Kutta discretization and the Pontryaguin maximum principle are used. Discretization scheme provides a sufficiently high order requiring a computation of the partial derivatives of the aircraft dynamic parameters. The nonlinear interior point trust region optimization solver is applied. Numerical experiments and results are presented. They confirm the feasible optimized trajectories contributing to a significant noise reduction.
Incidence du carcinome hépatocellulaire lors de l’infection chronique par le virus de l’hépatite B
(Pan African Medical Journal, 2015) Ntagirabiri, Rénovat; Munezero, Bélyse; Kaze, Hippolyte; et al.
Introduction: le virus de l'hépatite B (VHB) est incriminé comme cause de cancer primitif du foie. Le stade de fibrose et d'autres facteurs environnementaux et génétiques seraient intriqués. Le but de notre travail était de déterminer l'incidence du carcinome hépatocellulaire (CHC) lors d'une infection chronique par le VHB et estimer le risque relatif (RR) de CHC lié au stade de la fibrose hépatique. Méthodes: étude prospective de suivi d'une cohorte de patients porteurs chroniques du VHB sur une période de 5 ans (2009 à 2014). Etaient inclus les patients consécutifs qui ont subi un dosage de la charge virale B, une évaluation de la fibrose hépatique et un suivi régulier de tous les 6 à 12 mois par une échographie hépatique. Résultats: au total 194 patients ont été retenus. L'âge moyen était de 39,1 ans. Parmi eux 112 étaient des hommes. L'incidence cumulée de CHC a été de 8,8% dans la population d'étude soit une incidence annuelle de 1,8%. Selon le stade de fibrose, 31 patients avaient une fibrose sévère ou une cirrhose (score Fibrotest >0,73). Parmi eux, l'incidence cumulée de CHC était de 35,5% soit une incidence annuelle estimée à 7,10%. Parmi 163 patients ayant une fibrose mineure, l'incidence cumulée de CHC était de 3,7% soit une incidence annuelle de 0,7%. Le RR lié à la cirrhose était de 9,7; IC 95%: (3,8-24,1%). Conclusion: le VHB expose au CHC jusqu'à 10 fois. La fibrose sévère et la cirrhose constituent des facteurs prédictifs de CHC chez le porteur chronique du VHB. Evaluer systématiquement la fibrose pour traiter précocement les malades pourra prévenir l'évolution vers la cirrhose et par là réduire la survenue du CHC.
Pontryagin Principle Applied to Commercial Aircrafts Optimal Control Problem under Physical and Energetic Constraints
(ICSRS Publication, 2017) Nahayo, Fulgence
The objective of this work is the development of a control and optimization flight paths model minimizing fuel consuption and noise perceived on the ground for two aircraft when flight constraints are considered. Flight dynamics, combined with the criterion to minimize noise levels generates an optimal control problem governed by nonlinear di erential equations . This problem is solved using an indirect method applying the minimum principle of Pontryagin and a dynamic programming method. Obtained optimal results showed signi cant reductions of fuel consumption and noise levels. This model shows and con rm environmental Approach impact around airport by reduction of the gene for neighbors due to noise. Reduction of Economic cost to airlines and for builders are also con rmed. An optimal approach path when compared to standard flight path is con rmed.This model can be generalized for any type of aircraft when considering real case for airport traffic and air traffic.
La Recherche-Développement à l’Université du Burundi : bilan, défis et perspectives
(RUFORUM Working Document Series, 2018) Masharabu, Tatien; Nahayo, F.; Bogaert, J.; Et al.
Créée en 1964, l’Université du Burundi est la principale université publique du pays. En 2017, elle compte 9300 étudiants reparties à travers huit facultés et trois instituts, avec un effectif de l’ordre de 237 enseignants-chercheurs détenteurs d’un doctorat (PhD) et de 275 assistants toutes catégories, opérant dans 13 centres de recherche sur diverses thématiques pluridisciplinaires du pôle des Sciences Naturelles, de la Vie et de l’Ingénieur, et du pôle des Sciences Humaines et Sociales. Après plus d’un demi-siècle d’enseignement, de recherche et de services à la communauté, quel serait le bilan de sa production scientifique? Malgré les défis auxquels font face le Burundi et l’Afrique, l’Université du Burundi occupe la première place à l’échelle nationale, la 91ème place à l’échelle continentale, et la 5225 ème place à l’échelle planétaire sur base des indicateurs établis par Ranking Web ofUniversities dans le cadre du classement mondial des universités. Alors que la Recherche-Développement (R-D) peut et doit contribuer à trouver des solutions aux différents défis de la société (l’insécurité alimentaire, la crise énergétique, les problèmes de financement, les changements climatiques, la santé publique, etc.), il faudrait que le secteur de la R-D soit doté de bons indicateurs et instruments. Et tout laisse entendre qu’il est possible de transformer ces défis en opportunités de collaboration et/ou d’affaires à l’échelle locale, régionale et internationale. Burundi, Indicateurs, Innovation, Recherche-Développement
The AppliedMathematical SimulationModeling Algorithm for a Multi Aircraft Landing Dynamic System at Bujumbura International Airport Mathematics and Innovative Technologies in Africa
(European Scientific Journal, 2019) Nahayo, Fulgence; Ndimubandi, J.; Manirabona, A.; Niyongere, A.
The aim of this paper is to set up an efficient nonlinear application algorithm simulation model for a multi aircraft landing dynamic system in one Runway when considering Bujumbura International Airport. The mathematical modelization of the solved problem is a non-convex optimal control governed by ordinary non-linear differential equations.The dynamic programming technic is applied because it is a sufficiently high order and it does-not require computation of the partial derivatives of the aircraft dynamic. This application is be coded with Linux operating system, but it can also be run on the windows system. High runing performance are obtained with results giving feasible trajectories with a robust optimizing of the objective function. The user interfaces designed in Glade are saved as XML, and by using the GtkBuilder GTK+ object these can be loaded by applications dynamically as needed. By using GtkBuilder, Glade XML files can be used in numerous programming languages including C, C++, C#, Java, Perl, Python,AMPL,etc.. Glade is Free Software released under the GNU GPL License. The algorithm is implemented when considering discrete mathematics while using Bujumbura International Airport Geographic Information System.
Towards Post-Quantum Cryptography Using Thermal Noise Theory and True Random Numbers Generation
(Journal of Information Security, 2020) Ndagijimana, P et al.
The advent of quantum computers and algorithms challenges the semantic security of symmetric and asymmetric cryptosystems. Thus, the implementation of new cryptographic primitives is essential. They must follow the breakthroughs and properties of quantum calculators which make vulnerable existing cryptosystems. In this paper, we propose a random number generation model based on evaluation of the thermal noise power of the volume elements of an electronic system with a volume of 58.83 cm3. We prove through the sampling of the temperature of each volume element that it is difficult for an attacker to carry out an exploit. In 12 seconds, we generate for 7 volume elements, a stream of randomly generated keys of 187 digits that will be transmitted from source to destination through the properties of quantum cryptography.
An Efficient Non-Linear Application Algorithm Predictive Model for a Multi Aircraft Landing Dynamic System AIRLADYS R2019A+
(Open Journal of Optimization, 2020) Nahayo, Fulgence; Khardi, Salah
The aim of this paper is to set up an efficient nonlinear application algorithm predictive model for a multi aircraft landing dynamic system called “Aircraft Landing Dynamic System, Release 2019A+ version “AIRLADYS R2019A+”. This programming software combines dynamic programming technic for mathematical computing and optimisation run under AMPL and KNITRO Solver. It uses also a descriptive programming technic for software design. The user interfaces designed in Glade are saved as XML, and by using the GtkBuilder GTK+ object these can be loaded by applications dynamically as needed. By using GtkBuilder, Glade XML files can be used in numerous programming languages including C, C++, C#, Java, Perl, Python, AMPL, etc. Glade is Free Software released under the GNU GPL License. By these tools, the solved problem is a mathematical modelization problem as a non-convex optimal control governed by ordinary non-linear differential equations. The dynamic programming technic is applied because it is a sufficiently high order and it does not require computation of the partial derivatives of the aircraft dynamic. This application will be coded with Linux system on 64 bit operating system, but it can also be run on the windows system. High running performances are obtained with results giving feasible trajectories with a robust optimizing of the objective function.
Qualité perçue de services financiers et recours au financement externe formel par les petites et moyennes entreprises (PME) de Bukavu en RDC : rôle modérateur de l’état civil
(Revue Internationale du Chercheur, 2020) Mmenge, Adolphe; Gahungu, Dieudonné
Cette étude mesure la qualité perçue de services financiers et teste le rôle modérateur de l’état civil dans la relation entre la qualité perçue de services financiers et des Petites et moyennes entreprises de la ville de Bukavu en République Démocratique du Congo en identifiant les dimensions de la qualité perçue plus significative dans l’explication de recours au financement externe formel. Elle analyse les données primaires collectées sur 250 PME de la ville de Bukavu. Le traitement des données a été obtenu en recourant à l’analyse factorielle exploratoire et confirmatoire et à la régression. Les résultats indiquent que l’état civil module la force de relation entre la qualité perçue des services financiers et le recours au financement externe formel des PME. Ils montrent que la qualité perçue des services financiers est un construit à huit items regroupés en trois dimensions (la tangibilité, la fiabilité et la serviabilité). Ils révèlent aussi que la fiabilité et la serviabilité sont les dimensions de la qualité perçue qui influencent positivement et significativement le recours au fond externe formel par les PME de la ville de Bukavu.
Understanding the influence of the COVID-19 pandemic on hospital-based mortality in Burundi: a cross-sectional study comparing two time periods
(Cambridge University Press, 2020) Habonimana, D. et al.
This study used hospital records from two time periods to understand the implication of COVID-19 on hospital-based deaths in Burundi. The place of COVID-19 symptoms was sought among deaths that occurred from January to May 2020 (during the pandemic) vs. January to May 2019 (before the pandemic). First, death proportions were tested to seize differences between mortality rates for each month in 2020 vs. 2019. In the second time, we compared mean time-to-death between the two periods using the Kaplan–Meier survival curve. Finally, a logistic regression was fitted to assess the likelihood of dying from COVID-19 symptoms between the two periods. We found statistical evidence of a higher death rate in May 2020 as compared to May 2019. Moreover, death occurred faster in 2020 (mean = 6.7 days, S.D. = 8.9) than in 2019 (mean = 7.8 days, S.D. = 10.9). Unlike in 2019, being a male was significantly associated with a much lower likelihood of dying with one or more COVID-19 symptom(s) in 2020 (odds ratio 0.35, 95% confidence interval 0.14–0.87). This study yielded some evidence for a possible COVID-19-related hospital-based mortality trend for May 2020. However, considering the time-constraint of the study, further similar studies over a longer period of time need to be conducted to trace a clearer picture on COVID-19 implication on hospital-based deaths in Burundi
Treatment of Fracture Dislocation of the Femoral Head in a Resource Limited Country (Burundi)
(Open Journal of Orthopedics, 2020) Ndayizeye, G. et al.
Introduction: Fractures of the femoral head are rare injuries which generally follow a traumatic dislocation of the hip or in a poly-trauma scenario. A fracture dislocation of the femoral head is an orthopedic emergency. The most frequent complications after a fracture of the femoral head are osteonecrosis, post traumatic arthritis and heterotopic ossification. Objective: To focus on the therapeutic aspect of fracture-dislocations of femoral head and their short- and long-term prognoses. Materials and Methods: This is a prospective study conducted at Kamenge teaching hospital and Rohero Christian medical and surgical clinic from January 2013 to August 2020. All patients diagnosed with fracture-dislocations of the femoral head were included in this study. Results: Five patients were admitted for fracture dislocation of the femoral head. The mean age was 40.4 years and varied between 25 and 55 years. The dashboard injury was the most common mechanism and was found in four patients (80%). A standard x-ray was performed for the five patients as well as CT scans in two cases. All patients had posterior iliac dislocations with fractures of the femoral head classified as Pipkin I in three patients and Pipkin III in two patients. Closed reduction under general anesthesia within six hours was possible in one among the five patients and within 12 hours in two patients. These three cases were managed with open reduction showed fracture union without avascular necrosis, posttraumatic arthritis or heterotopic ossification. The functional results for the five patients with an average follow up of four years were very good (3/5) and good (2/5). Conclusion: The diagnosis of fracture dislocations of the femoral head was based on clinical, radiographic and computed tomography criteria. Early reduction and internal fixation can restore the natural anatomy of the hip joint, especially in young adults with a good long-term prognosis. Sometimes total hip replacement is necessary for management of fracture dislocations of the femoral head.
Unilateral Femoral Neck Fracture after Epileptic Seizure in Young Patient: A Case Report
(Open Journal of Orthopedics, 2020) Niyondiko, J. C. et al.
Femoral neck fracture occurring after an epileptic seizure is a rare and underdiagnosed injury. The majority of the reported cases in literature are old patients with osteoporosis. Younger patients present several risk factors of osteopenia and the treatment remains controversial. We present an outcome of a 23 years old patient with unilateral femoral neck fracture occurring during an epileptic seizure and we discuss the associated multiple risk factors of osteopenia and osteonecrosis of the hip. The patient was brought to the emergency department of Teaching Hospital of Kamenge (CHUK) complaining of pain in his left hip that had been progressing for one month after an epileptic seizure. There is a history of HIV infection since birth and epileptic seizures with ongoing treatments for both diseases. Despite the high risk of avascular necrosis, the treatment choice has been influenced by the patient’s age and a conservative surgery by internal fixation with Dynamic Hip Screw has been made. Unfortunately, this treatment early resulted in osteonecrosis of the hip since HIV infection itself and the highly active anti-retroviral therapy increase its risk.
Optimal Predictive Algorithm for the Pickup and Delivery Problem with Time Windows and Scheduled Lines: Innovative Routing Transport Systems
(Applied Mathematical Sciences, Vol. 14, 2020) Nahayo, Fulgence; Bigirimana , M.
This paper concerns the Pickup and Delivery Problem with Time Windows and Scheduled Lines "PDPTW-SL" by modeling it mathematically on the one hand with the help of dynamic programming, on the other hand, it presents two optimal predictive methods of combinatorial optimization intended to solve it and which must provide stable and high accuracy solutions. The Pickup and Delivery Problem with Time Windows and Scheduled lines aims at routing a given set of vehicles to transport freight requests from their origins to their corresponding destinations, where the requests can use scheduled passenger transportation services during a stump of their journeys. We describe the PDPTW-SL as a mixed-integer program. Computational results on a set of small-size instances provide a clear understanding of the bene ts of preprocessing step and valid inequalities using scheduled line services as a part of freights journey.
Statistics Analysis Towards Capturing Comparison Between Taxation Systems of Neighboring Economies Versus DRC Taxation System
(Applied Mathematical Sciences, 2021) Byamungu, Wanguwabo David; Nahayo, Fulgence; Fono, Louis Aimé
Tax determinants are factors with tax system including collection machinery, penal system and tax rate and this differs from a country to another because of the strength of political institutions, efficient tax collection systems, tax rate. We deal with comparison of tax treatment of DRC to what applied to Rwanda, Tanzania, Uganda and Burundi as transit countries for goods of Congolese traders to determine whether the fluctuation underlying the problem of our study is due to the difference in tax collection model or the tax rate or if it is linked to another variable. Dealing with this, a quantitative questionnaire with open and closed questions, scaled values consisting in collecting various assessments of Congolese traders in import-export sector has been submitted to 340 taxpayers randomly selected. Through t-test analysis, Analysis of Variance and Chi-square results reveal that: tax rate is low in neighboring countries versus the highest tax rate in DRC applied to the same traders ‘goods. The statistically significant difference between different import products based on cross-border trade in the assessment of tax rate, on the one hand, and the relationship observed between the type of imported goods and the tax rate, on the other hand, proves the fact that in neighboring countries the tax administration sets the tax according to the types of goods and its weight while tax rate does depend on goods’ nomenclature declared in DRC.The degree of governance in tax administration is on of important factors to improve in tax revenues matters. Neighboring countries, as DRC, taxpayers with higher education level have civism development and higher attitudes towards more compliance. Finally, statistics reveal out that there is no statistically difference in attitudes towards tax compliance between male and female in DRC as in transit countries.
Aloe and its Effects on Cancer : A Narrative Literature Review
(East African Health Research Journal | Volume 5, 2021) Manirakiza, Astère; Irakoze, Laurent; Manirakiza, Sebastien
Many years ago, Aloe Vera was cited to have a lot of therapeutic properties including; anti-microbial, anti-viral, anti-cancer, anti-oxidant, anti-inflammatory, skin protection, wound healing, and regulation of blood glucose and cholesterol. However, Aloe could present some side effects. This review focused on the latest discoveries regarding the therapeutic role of Aloe plant or its compounds on the acquired biological capabilities for tumour growth and progression namely; evading growth suppressor, avoiding immune destruction, enabling replicative immortality, tumour promoting inflammation, activating invasion and metastasis, inducing angiogenesis, genome instability and mutation, resisting cell death, deregulating cellular energetics and sustaining proliferating signalling. It clarified the anti-cancer activities it exerts on different types of cancer and also highlighted some pro-oncogenic pathways that can be disrupted by different compounds of Aloe.
Assessment of Knowledges, Attitudes, and Practices of Health Personnel with Regard to Hypertension During Pregnancy in Hospitals of Bujumbura
(Indian Journal of Clinical Cardiology, 2021) Ndirahisha et al.
Objective: To assess knowledges, attitudes, and practices of health personnel in Bujumbura hospitals with regard to hypertension during pregnancy. Methodology: This study has been conducted on health personnel of gynecology and obstetrics department of three national referral hospitals in Bujumbura. It is a descriptive cross-sectional study to assess knowledge, attitudes, and practices. Data were collected by a questionnaire and analyzed by Epi Info 7.2. Results: In a total of ninety-seven health workers participated in our study and 78.3% were paramedics with 53.6% of nurses and 24.7% of midwives. Medical doctors represented 21.6% of the participants. The sex ratio was 1.4 in favor of women. The professional experience was more than 5 years for 64.9% of participants. Concerning knowledge about hypertension; 74.2% of participants correctly defined hypertension during pregnancy. Despite this, only 48.4% respected conditions about its measurement. concerning attitude toword hypertension; 94.8% of participants informed their patients about the risks linked to hypertension in pregnancy before any therapeutic strategy. The antihypertensive drugs contraindicated during pregnancy were known by 54.6% of participants. To prevent preeclampsia, low doses of aspirin and calcium were prescribed by 42.2% of participants. Conclusion: Hypertension during pregnancy is a worrying situation for health personnel, which still has many theoretical and practical gaps
Predictive Mathematical and Statistical Modeling of the Dynamic Poverty Problem in Burundi: Case of an Innovative Economic Optimization System
(Open Journal of Optimization, 2021) Nahayo, Fulgence; Bagorizamba, Ancille; Bigirimana, Marc; Et al.
The mathematical and statistical modeling of the problem of poverty is a major challenge given Burundi’s economic development. Innovative economic optimization systems are widely needed to face the problem of the dynamic of the poverty in Burundi. The Burundian economy shows an inflation rate of −1.5% in 2018 for the Gross Domestic Product growth real rate of 2.8% in 2016. In this research, the aim is to find a model that contributes to solving the problem of poverty in Burundi. The results of this research fill the knowledge gap in the modeling and optimization of the Burundian economic system. The aim of this model is to solve an optimization problem combining the variables of production, consumption, budget, human resources and available raw materials. Scientific modeling and optimal solving of the poverty problem show the tools for measuring poverty rate and determining various countries’ poverty levels when considering advanced knowledge. In addition, investigating the aspects of poverty will properly orient development aid to developing countries and thus, achieve their objectives of growth and the fight against poverty. This paper provides a new and innovative framework for global scientific research regarding the multiple facets of this problem. An estimate of the poverty rate allows good progress with the theory and optimization methods in measuring the poverty rate and achieving sustainable development goals. By comparing the annual food production and the required annual consumption, there is an imbalance between different types of food. Proteins, minerals and vitamins produced in Burundi are sufficient when considering their consumption as required by the entire Burundian population. This positive contribution mains in deficit. The lipids, acids, calcium, fibers and carbohydrates produced in Burundi are insufficient for consumption. This negative contribution proves a Burundian food deficit. It is a decision-making indicator for the design and updating of agricultural policy and implementation programs as well as projects. Investment and economic growth are only possible when food security is mastered. The capital allocated to food investment must be revised upwards. Demographic control is also a relevant indicator to push forward Burundi among the emerging countries in 2040. Meanwhile, better understanding of the determinants of poverty by taking cultural and organizational aspects into account guides managers for poverty reduction projects and programs.

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