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Chaos-Based Encryption of ECG Signals: Experimental Results

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Journal of Biomedical Science and Engineering 2014年第6期7卷 368-379页

作者： Gutenbert Kenfack alain tiedeu LETS GRETMAT National Advanced School of Engineering University of Yaoundé I Yaoundé Cameroon

In this work, we suggest a system for chaos-based encryption of electrocardiographic signals. It uses simple electronics organized around a colpitts chaotic oscillator. The system has been designed, implemented and tested. The encrypted signal has been decrypted and compared to the original ECG signal. Experimental results were analysed and proved encouraging.

关键词： ECG Colpitts Oscillator Chaos Encryption Decryption

Extracting and smoothing contours in mammograms using Fourier descriptors

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Journal of Biomedical Science and Engineering 2014年第3期7卷 119-129页

作者： Cyrille K. Feudjio alain tiedeu Marie-Laure Noubeg Mihaela Gordan Aurel Vlaicu Samuel Domngang Centre Mère et Enfant Fondation Chantal Biya Yaoundé Cameroun CTMED Technical University of Cluj-Napoca Cluj-Napoca Romania Faculty of Science University of Yaoundé I Yaoundé Cameroon LETS GRETMAT National Advanced School of Engineering Yaoundé Cameroon

Contour is an important pattern descriptor in image processing and particularly in region description, registration and length estimation. In many applications where contour is used, a good segmentation and an efficient smoothing method are needed. In X-ray images, such as mammograms, where object edge is not clearly discernible, estimating the object’s contour may yield substantial shift along the boundary due to noise or segmentation drawbacks. An appropriate smoothing is therefore required to reduce these effects. In this paper, an approach based on local adaptive threshold segmentation to extract contour and a new smoothing approach founded on Fourier descriptors are introduced. The experimental results of extraction obtained from a set of mammograms and compared with the breast regions delineated by radiologists yielded a percent overlap area of 98.7% ± 0.9% with false positive and negative rates of 0.36 ± 0.74 and 0.93 ± 0.44 respectively. The proposed method was tested on a set of images and improved the accuracy, leading to an average error of less than one pixel.

关键词： Mammogram Segmentation Breast Contour Smoothing Fourier Descriptors

Crustal structure beneath Cameroon from EGM2008

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Geodesy and Geodynamics 2014年第1期5卷 1-10页

作者： Ngatchou Heutchi Evariste Liu Genyou Tabod Charles Tabod Kamguia Joseph Nguiya Severin tiedeu alain KE Xiaoping State Key Laboratory of Geodesy and Earth's Dynamics Institute of Geodesy and GeophysicsChinese Academy of Sciences Department of Physics Faculty of ScienceUniversity of Yaoundé I National Institute of Cartography Industrial Engineering Faculty University of Douala Ecole Nationale Supérieure Polytechnique Université de Yaoundé I

We used the Earth Gravitational Model （EGM2008） data sets to analyze the regional gravity anoma- lies and to study the underground structures in Cameroon. We first created a high-resolution Free-Air anomaly database, then corrected the gravity field of the topographic effect by using ETOPO1 DEM with a resolution of 0.01~ to obtain the Bouguer anomaly, then applied a multi-scale wavelet-analysis technique to separate the gravity-field components into different parts of shallow-to-deep origins, and finally used the logarithmic power spectrum technique to obtain detailed images and corresponding source depths as well as certain lateral inho- mogeneity of structure density. The anomalies of shallow origin show successive elongated gravity ＂highs＂ and ＂lows＂ attributable to subsurface Tertiary and lower Cretaceous undulations. Our results are in good agreement with previous investigations.

关键词： Cameroon EGM2008 gravity anomalies wavelet transform power spectrum crustal structure

Design of a Neural Network Based Stable State Observer for Mimo Systems

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Journal of Computer and Communications 2023年第11期11卷 87-110页

作者： Jean Gutenbert Kenfack Wamba Eric Michel Deussom Djomadji Jean Claude Lionel Ng’anyogo Arsene Roger Bienvenu Fouba alain tiedeu Department of Electrical and Telecommunications Engineering National Advanced School of Engineering of Yaoundé University of Yaoundé I Yaoundé Cameroon Division of ICT National Advanced School of Post Telecommunication and ICT University of Yaounde I Yaoundé Cameroon Department of Electrical and Electronic Engineering College of Technology University of Buea Buea Cameroon

MIMO (Multiple Input Multiple Output) is a key technology underpinning fourth generation or 4G networks. This technology allows 4G networks to increase throughput. However, the dynamics of the MIMO system are not under control due to the many uncertainties that destabilize the system. This work is therefore very relevant in the sense that an observer can be used to monitor the dynamics of such a system. This work presents a neuro-adaptive observer based on a radial basis function neural network for generic non-linear MIMO systems. Unlike most neuro-adaptive observers, the proposed observer uses a neural network that is non-linear in its parameters. It can therefore be applied to systems with high degrees of nonlinearity without any a priori knowledge of the system dynamics. Indeed, in addition to the fact that neural networks are very good nonlinear approximators, their adaptive behavior makes them powerful tools for observing the state without any a priori knowledge of the dynamics of the system. The learning rule of the neural network is an approach based on the modified backpropagation algorithm: A term has been added to guarantee the robustness of the observer. The proposed approach is not limited by a strong assumption. The stability of the neuro-adaptive observer is demonstrated by the direct Lyapunov method. Simulation results are presented in the context of MIMO signal transmission applied in LTE, to demonstrate the performance of our observer.

关键词： Stability Neural Network MIMO LTE Network Lyapunov Function

A power function model for simulating creep mechanical properties of salt rock

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Journal of Central South University 2020年第2期27卷 578-591页

作者： LI Huan Ngaha tiedeu WILLIAM Jaak DAEMEN ZHOU Jun MA Chang-kun State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China School of Civil and Environmental Engineering University of Chinese Academy of SciencesBeijing 100049China School of Resources and Environmental Sciences Chongqing UniversityChongqing 400044China Mackay School of Earth Sciences and Engineering University of NevadaRenoNVUSA

In this paper,a new micro-creep model of salt rock is proposed based on a linear parallel bonded model(LPBM)using the two-dimensional particle flow code(PFC2D).The power function weakening form is assumed to describe the variation of the parallel bonded diameter(PBD)over *** comparing with the parallel-bonded stress corrosion(PSC)model,a smaller stress fluctuation and smoother creep strain−time curves can be obtained by this power function model at the same stress *** validity and adaptability of the model to simulate creep deformation of salt rock are verified through comparing the laboratory creep test curves and the Burgers model fitting *** numerical results reveal that this model can be capable of capturing the creep deformation and damage behavior from the laboratory observations.

关键词： salt rock creep damage particle flow code power function model

Antioxidant properties of cell wall polysaccharides of Stevia rebaudiana leaves

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Journal of Coastal Life Medicine 2014年第12期 962-969页

作者： Mediesse Kengne Francine Woguia Alice Louise Fogue Souopgui Pythagore Atogho-tiedeu Barbara Simo Gustave Thaddée Boudjeko Laboratory of Phytoprotection and Valorization of Plants Resources Biotechnology Centre-NkolbissonPo.Box 3851MessaYaoundeCameroon Department of Biochemistry Faculty of ScienceUniversity of Yaounde IPo.Box 812 YaoundeCameroon Department of Biochemistry Faculty of ScienceUniversity of DschangPo.Box 67 DschangCameroon Laboratory for Metabolic and Molecular Medicine Biotechnology Centre-NkolbissonPo.Box 3851MessaYaoundeCameroon

Objective:To examine the total phenolic and protein contents,and the antioxidant activities of cell wall polysaccharide fractions of Stevia rebaudiana ***:Three different polysaccharide-enriched fractions,namely FPE(extract with 50 mmol/L ethylene diamine tetra acetic acid),FPK(extract with 0.05 mol/L KOH)and FH(extract with 4 mol/L KOH)were extracted from Stevia rebaudiana *** antioxidant activity of these fractions was evaluated based on their ability to scavenge DPPH(1,1-diphenyl-2-picryl hydrazyl)free radical,to reduce ferric power,to chelate ferrous ion and to protect human ***:The results indicated that protein content was found to be higher in FPK polysaccharide enriched fraction(47.48μg per mg of FPK).Furthermore,the phenolic compound analysis according to the Folin-Ciocalteu method was higher in FPK(17.71μg ferulic acid).The DPPH maximal inhibition percentage of the three polysaccharide-enriched fractions at 400μg/mL was 27.66%,59.90%and 23.21%respectively for FPE,FPK and *** the polysaccharide fractions exhibited a ferric reducing power except the FH *** three fractions also exhibited lipid peroxidation inhibition,and they completely reverted the DNA damage induced by H_(2)O_(2)/FeCl_(2).FPK showed the strongest scavenging activity against the DPPH radical,the best chelating ability and lipid peroxidation ***:Stevia cell wall polysaccharide fractions are potent protective agents against oxidative *** analysis revealed major differences in the antioxidant activity in the three polysaccharides ***,the 0.05 mol/L KOH pectin fraction(FPK)showed better antioxidant activity.

关键词： Stevia rebaudiana Cell wall polysaccharides Fractions Antioxidant properties

Genetic Predisposition for Type 2 Diabetes Mellitus in a Cameroonian Population: Contribution of rs4731702 (C/T) Polymorphism of Krüppel-Like Factor 14 Gene

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Open Journal of Genetics 2021年第2期11卷 9-22页

作者： Magellan Guewo-Fokeng Eugene Sobngwi Barbara Atogho-tiedeu Eric Lontchi-Yimagou Jean-Paul Chedjou Jean-Claude Mbanya Wilfred F. Mbacham Department of Biochemistry Faculty of Medicine and Biomedical Sciences University of Yaoundé I Yaoundé Cameroon The Biotechnology Centre University of Yaoundé I Nkolbisson Yaoundé Cameroon Department of Internal Medicine and Specialties Faculty of Medicine and Biomedical Sciences University of Yaoundé I Yaoundé Cameroon Department of Biochemistry Faculty of Science University of Yaoundé I Yaoundé Cameroon

Introduction: Krüppel Like Factor 14 (KLF14) gene has recently been identified as a master gene for multiple metabolic phenotypes. The aim of the research study was to investigate the relationship between KLF14 rs4731702 (C/T) gene polymorphism with Type 2 Diabetes Mellitus (T2DM) in a Cameroonian population. Patients and Methods: This case-control study was conducted in 85 patients with T2DM and 95 healthy normoglycemic controls. All were nonrelated, of Cameroonian origin, and were adults aged 24 years old and above. Demographic, clinical and biological data were collected, and biochemical explorations were performed using enzymatic colorimetric methods. The genotyping of KLF14 rs4731702 (CT) gene polymorphism was done by the Polymerase Chain Reaction and Restriction Fragment Length Polymorphism. Results: In comparing the Cameroonian population that consisted of 85 patients with T2DM and 95 healthy controls, the minor or risk allele of the rs4731702 (C/T) polymorphism of the KLF14 gene was T (63.53% diabetic patients vs. 26.32% healthy controls, OR = 4.877 and p Conclusion: This study has demonstrated for the first time the relationship between the KLF14 rs4731702 (C/T) gene polymorphism and T2DM in this Cameroonian population. This gene polymorphism could be a promising target for personalized medicine through the development of clinical genetic testing.

关键词： Genetic Krüppel-Like Factor 14 Gene Type 2 Diabetes Mellitus Cameroon

Automated Exudates Detection in Retinal Fundus Image Using Morphological Operator and Entropy Maximization Thresholding

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Journal of Biomedical Science and Engineering 2019年第3期12卷 212-224页

作者： G. H. Kom B. C. Wouantsa Tindo J. R. Mboupda Pone A. B. tiedeu Research Unit of Automation and Applied Informatics (URAIA) Department of Electrical Engineering IUT-FV Bandjoun University of Dschang Bandjoun Cameroon Research Group on Medical Technologies Applied to the Tropics (GRETMAT) Laboratory of Electronics and Signal Processing (LETS) ENSP University of Yaoundé I Yaoundé Cameroon Research Unit for Condensed Matter Electronics and Signal Processing (LAMACETS) Department of Physics University of Dschang Dschang Cameroon Signal Image and Systems Laboratory Ebolowa Cameroon

Blindness which is considered as degrading disabling disease is the final stage that occurs when a certain threshold of visual acuity is overlapped. It happens with vision deficiencies that are pathologic states due to many ocular diseases. Among them, diabetic retinopathy is nowadays a chronic disease that attacks most of diabetic patients. Early detection through automatic screening programs reduces considerably expansion of the disease. Exudates are one of the earliest signs. This paper presents an automated method for exudates detection in digital retinal fundus image. The first step consists of image enhancement. It focuses on histogram expansion and median filter. The difference between filtered image and his inverse reduces noise and removes background while preserving features and patterns related to the exudates. The second step refers to blood vessel removal by using morphological operators. In the last step, we compute the result image with an algorithm based on Entropy Maximization Thresholding to obtain two segmented regions (optical disk and exudates) which were highlighted in the second step. Finally, according to size criteria, we eliminate the other regions obtain the regions of interest related to exudates. Evaluations were done with retinal fundus image DIARETDB1 database. DIARETDB1 gathers high-quality medical images which have been verified by experts. It consists of around 89 colour fundus images of which 84 contain at least mild non-proliferative signs of the diabetic retinopathy. This tool provides a unified framework for benchmarking the methods, but also points out clear deficiencies in the current practice in the method development. Comparing to other recent methods available in literature, we found that the proposed algorithm accomplished better result in terms of sensibility (94.27%) and specificity (97.63%).

关键词： Diabetic Retinopathy Retinal Fundus Image Exudates Entropy Maximization Thresholding

Predominance of Plasmodium malariae-falciparum Co-Infection by Molecular Speciation in Bangolan, North West Region of Cameroon

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Journal of Life Sciences 2013年第6期7卷 599-606页

作者： Olivia Afa Achonduh Aristid Herve Ekollo Mbange Atogho-tiedeu Barbara Innocent Ali Mbulli Daniel Achinko Palmer Masumbe Netongo Wilfred Fon Mbacham The Bioteehnology Center University of Yaounde I Yaounde Center Region Cameroon

Although microscopy still remains the gold standard for the diagnosis of malaria, rapid diagnostic tests （RDTs） and PCR assays have been shown to be sensitive and specific. Very few comparative studies have been reported of the three diagnostic methods on the same samples in vulnerable groups. Microscopy, RDTs and PCR assays were used for detection and speciation of Plasmodium falciparum （P）＇）, Plasmodium malariae （Pm） and Plasmodium ovale （Po） in patients in a rice culture savanna ecotype. Fifty four children and 16 pregnant women presenting with a fever were recruited. Bloods collected was used for thin and thick smears, perform RDTs and spotted blood on filter paper for DNA extraction and performance of a PCR. Mean parasitaemia was 37,619.06 （＋ 33,599.04） p/pL and 7,512.5 （＋ 12,446.11） p/μL for children and pregnant women, respectively. A total of 87.14% were positive by microscopy, 85.71% by RDTs and 90% by PCR. Distribution of Plasmodium species as identified by PCR was 72.86% Pf/Pm, 11.43% Pf/Pm/Po and 5.43% Pm while 10% were negative. Cohen＇s Kappa value for PCR and RDTs was K = 0.75 （CI = 0.28-1.22） while PCR and microscopy was K = 0.64 （CI = 0.18-1.10）. Malaria infection in Bangolan was mostly due to mix infection predominantly P. falciparum/P, malariae.

关键词： Plasmodium sp. microscopy rapid diagnostic tests PCR children pregnant women.