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World Journal of Engineering and Technology 2021年第1期9卷 15-25页

作者： Brice Poumegne Kouam Didier Fokwa Dieunedort Ndapeu Médard Fogue Research Unit of Mechanics and Physical Systems Modeling of (UR2MSP) Department of Physics Faculty of Science Uni-versity of Dschang Dschang Cameroon Research Unit of Engineering of Industrial Systems and Environment (URISIE) IUT/FV Bandjoun Department of Physics Faculty of Science University of Dschang Dschang Cameroon Laboratory of Mechanics (LM) Department of Civil Engineering Advanced Teacher’s Training College for Technical Educa-tion University of Douala Douala Cameroon Laboratory of Mechanics and Appropriate Materials (LAMMA) Department of Civil Engineering Advanced Teacher’s Training College for Technical Education University of Douala Douala Cameroon

The bamboo stem, when mature 5 to 6 years, serves as a building material for modest houses and its marrow as packaging purposes. One of the strains related to the uses of bamboo stem is most often the compression towards the axial direction. The phenomenon of damage is very often observed during such loading. The present study on raffia aims to analyze this phenomenon through cyclical stresses as usual. From the results obtained, it was observed in the stress-strain plane, that the area of the hysteresis loops and the residual strain evolve with two parameters: the number of cycles and the stress peaks. The study of energy dissipation has shown that it evolves according to an exponential law as a function of the number of cycles. The distribution of the energy rate along a stem shows that the samples from the zone close to the base store twice (0.0412 MJ/m3) more energy than the samples taken from the top of the foliage (0.019 MJ/m3).

关键词： Bamboo Raphia Cyclic Compression Energy Dissipation

Regional Intrusive Signature from the Cameroon Coastal Basins to Bioko Island in Equatorial Guinea (Gulf of Guinea) Using Gravity Studies

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

作者： Eric N. Ndikum Charles T. Tabod Department of Physics HTTC Bambili The University of Bamenda Bamenda Cameroon Department of Fundamental Sciences Higher Technical Teacher Training College (HTTTC) Bamenda Cameroon Department of Physics University of Yaoundé 1 Yaoundé Cameroon Department of Physics Faculty of Science The University of Bamenda Bamenda Cameroon

The Gulf of Guinea constitutes an area of great petroleum potential yet with very limited geophysical research information. Consequently in this study, a Bouguer anomaly map has been computed from gravity data covering regions stretching from the Cameroon coastal basins to Bioko island (formerly Fernando Po) which is part of Equatorial Guinea. The data were further processed for Source Edge Detection (SED), Euler 3D deconvolution, 3D surface oriented models and 3D voxel solutions. The results confirmed the presence of previously identified intrusive bodies around the Douala and Kribi/Campo sedimentary sub-basins and went ahead to suggest a probable continuity between these two. A possible extension of this body offshore the Gulf of Guinea right up to Bioko island with very striking similarities was also highlighted and it shows characteristic variations in the depth to the surface of the body at different locations.

关键词： Intrusive Body 3D Surface-Oriented Model Gulf of Guinea

Mining Implication in the Geochemical Exploration of Fluvial Sediments of the East Nyambaka Volcanic Zone (Adamawa-Cameroon)

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International Journal of Geosciences 2022年第5期13卷 361-381页

作者： Roland William Edima Yana Augustin Désiré Balla Ondoa Lise Carole Okomo Atouba Mefire Aminatou Fagny Armel Zacharie Ekoa Bessa Nkouandou Oumarou Faarouk Centre for Geological and Mining Research Garoua Cameroon Department of Earth Sciences Faculty of Sciences University of Ngaoundere Ngaoundere Cameroon Higher teacher training college of Bertoua University of Ngaoundere Bertoua Cameroon Department of Earth Sciences Faculty of Sciences University of Yaounde I Yaounde Cameroon

Geochemical characterization in stream sediments from Nyambaka locality was carried out on ten samples collected from the study area watershed. The distribution of trace metals in the sediments showed that some lithophiles (Be, Sc, V, Cr, Sr, Th, U), chalcophiles (Cu, Zn, Ga, As) and siderophiles (Mn, Co, Ni, Mo) have high average contents in the sediments compared to their average concentration in the upper crust. From the factorial analysis of the components, the total variance explained made it possible to represent and capture the main information on the data and to represent them in a graphical frame. Thus, using this graphical frame, the trace elements were divided into four groups opposed to each other. They show an enrichment of stream sediments in group 1 (Cr, Cu, Mn, Be, Ni, Co, Zr, Sr, Ba, Mg) and group 2 (Mo, As, Hg, V, Ag) elements more than group 3 (Ga, Sc, U) and group 4 (Au, Th). Rare earth analysis indicates a high abundance of Lanthanide (28.1 ppm to 42.4 ppm), a high concentration of light rare earth (LREE), and depletion of heavy rare earth (HREE). The variable LREE/HREE (7.24 LREE/ HREE 12.22) and (La/Yb)N (6.70 (La/Yb)N 11.72) ratios suggest an effect of heterogeneous sorting of heavy minerals with variable enrichment of dense and resistant minerals.

关键词： Stream Sediments Geochemistry Mining Exploration Volcanic Zone East Nyambaka Cameroon

Applying Source Parameter Imaging (SPI) to Aeromagnetic Data to Estimate Depth to Magnetic Sources in the Mamfe Sedimentary Basin

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International Journal of Geosciences 2024年第1期15卷 1-11页

Aeromagnetic data over the Mamfe Basin have been processed. A regional magnetic gridded dataset was obtained from the Total Magnetic Intensity (TMI) data grid using a 3 × 3 convolution (Hanning) filter to remove regional trends. Major similarities in magnetic field orientation and intensities were observed at identical locations on both the regional and TMI data grids. From the regional and TMI gridded datasets, the residual dataset was generated which represents the very shallow geological features of the basin. Processing this residual data grid using the Source Parameter Imaging (SPI) for magnetic depth suggests that the estimated depths to magnetic sources in the basin range from about 271 m to 3552 m. The highest depths are located in two main locations somewhere around the central portion of the study area which correspond to the area with positive magnetic susceptibilities, as well as the areas extending outwards across the eastern boundary of the study area. Shallow magnetic depths are prominent towards the NW portion of the basin and also correspond to areas of negative magnetic susceptibilities. The basin generally exhibits a variation in depth of magnetic sources with high, average and shallow depths. The presence of intrusive igneous rocks was also observed in this basin. This characteristic is a pointer to the existence of geologic resources of interest for exploration in the basin.

关键词： Mamfe Basin Aeromagnetic Data Source Parameter Imaging (SPI) Depth to Magnetic Sources

Bioefficacy of Plectranthus kirbii Powder and Extracts on Stored Cowpea Pest Callosobruchus maculatus (Coleoptera: Chrysomelidae)

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Advances in Entomology 2022年第3期10卷 205-222页

作者： Jean Wini Goudoungou Félicité Arindo Katamssadan Haman Tofel Raoul Barry Borkeum Jean Pierre Abdou Elias Nchiwan Nukenine Department of Biological Sciences Faculty of Science University of Bamenda Cameroon Department of Biological Sciences Faculty of Science University of Ngaoundere Cameroon Department of Life Sciences Higher Teacher Training College of Bertoua University of Ngaoundere Cameroon Department of Chemistry Faculty of Science University of Ngaoundere Cameroon

Cowpea seed constitutes an important source of proteins for populations in Sub-Saharan Africa. But this food resource is heavily damaged by cowpea beetle Callosobruchus maculatus. The control of that pest is mainly carried out by using synthetic insecticides. Despite the efficacy of this method, it caused environmental and health problems. Therefore, the search for alternative methods is vivaciously needed. In this issue, the bio-efficacy of Plectranthus kirbii extracts was assessed on C. maculatus regarding adult mortality, suppression of population and grain damage as well as seed viability preservation and repellency. The leaf powder and aqueous extracts of the plant were tested at 2, 4, 8 and 16 g/kg on bruchid adult for toxicity and damage bioassays. Repellency test was carried out using the plant aqueous, methanolic and ethyl acetate extracts at 0.5, 1, 2 and 4 mg/cm2. The seed viability was evaluated using seeds preserved for three months at the single concentration of 16 g/kg of each plant extract. Significant mortality of cowpea beetle was induced by the plant aqueous extract and leaf powder. LC50 values decreased with the increasing exposure period, and aqueous extract and leaf powder recorded 33.42 and 9.48 g/kg respectively within 3 days whereas within 5 days, the same extracts in the same order recorded LC50 of 1.31 and 8.73 g/kg respectively. These extracts significantly reduced damage by suppressing almost completely the bruchid population growth. The non-infested grain preserved recorded high grain viability compared to the infested ones. The non-treated infested recorded the lowest germination rate (11.33%). The repellency rate ranged from 38.75% to 83.75%. Ethyl acetate and methanolic extracts were classified as the class III repellent product, while aqueous extract ranged as class IV in repellency. Considering these findings, the extracts of P. kirbii could favourably replace the synthetic insecticides used in the

关键词： Cowpea Beetle Plant Extracts Mortality Damage Viability

Analytical and Numerical Study of the Hydro-Mechanical Behavior of a Cantilever Retaining Wall in Upward Seepage Conditions

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World Journal of Engineering and Technology 2024年第4期12卷 914-937页

作者： Mbuh Moses Kuma Nsahlai Leonard Penka Jules Bertrand Kouamou Nguessi Arnaud Tchemou Gilbert Agandeh Elvis Phonchu Claret Abong Department of Civil Engineering and Forestry Techniques Higher Technical Teacher Training College University of Bamenda Bamenda Cameroon Department of Civil Engineering and Architecture The National Higher Polytechnic Institute (NAHPI) of the University of Bamenda Bamenda Cameroon Mechanics Laboratory ENSET of the University of Douala Douala Cameroon

Poor design of ground water evacuation mechanisms is often blocked and leads to the rise of ground water behind the wall. As a result, free water behind the wall that is not quickly evacuated, increases the lateral pressure and thus favors overturning failure. The resolution of the overturning problem in cantilever retaining walls caused by hydro-mechanical interaction was studied. An analytical and numerical method was used to study this type of wall-floor interaction. Then Coulomb’s design criterion against overturning to develop a mathematical model that compute analytical factor of safety against overturning in different water conditions and heel lengths was used. The modeling and simulation of this system in the Cast3m software which took into account a wide variety of floor and wall properties were performed. The numerical factor of safety against rollover was obtained, and the graphs for the factor of safety versus heel length and immersion depth for both methods were plotted. From (0 ≤ Hw ≤ H/3), water effect is not dangerous to wall stability against overturning and from (H/3 Hw ≤ H), water effect is very dangerous to wall stability against overturning. For analytical and numerical methods, the heel can be predimensioned against overturning as: Lc: [0.27H 0.38H], [0.29H 0.43H] for 0 ≤Hw ≤ H/3;[0.33H 0.45H], [0.39H 0.53H] for H/3 Hw ≤ 2H/3;[0.5H 0.6H], [0.50H 0.67H] for 2H/3 Hw≤ H. The numerical method guaranteeing more safety than the analytical method, Cantilever retaining walls can thus be pre-dimensioned considering Clayey-Sand soil in hydro-mechanical conditions.

关键词： Cantilever Retaining Wall Overturning Hydro-Mechanical Soil-Structure Interaction

Magnetotelluric Investigation of the Geo-Tectonic Stability of Campo-Ma’an Area in South Cameroon

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International Journal of Geosciences 2017年第12期8卷 1427-1441页

作者： Njingti-Nfor Owona Angue Marie Louise Clotilde Kue Petou Rokis Malquaire Bisso Dieudonne Piameu Kwagag Joel Postgraduate School of Sciences Technologies&GeosciencesUniversity of Yaounde IYaoundeCameroon Department of Physics Advanced Teacher Training CollegeUniversity of Yaounde IYaoundeCameroon National Institute of Cartography YaoundeCameroon School of Geosciences China University of PetroleumQingdaoChina

The magnetotelluric prospection method has been widely used in Cameroon not only as a reconnaissance method for geophysical investigations but also to determine the nature of the subsurface and the structural settings of the various geological formations in the country that resulted from the global geo-tectonic movements. The present study is aimed at employing the magnetotelluric method to provide evidence on major tectonic dislocations which might have led to the presence of plutonic intrusions in the cratonic structure of the Ntem Complex as well as determining the nature of the contact between the sedimentary Campo Basin and the metamorphic cratonic Ntem Complex. The analyses and interpretations of iso-resistivity maps and geoelectric sections from magnetotelluric data has enabled us to show that tectonic forces at contact between the sedimentary Campo Basin and the metamorphic Ntem Complex were of three different categories: gravity gliding, magmatic upwelling and lateral compressions. The results of the action of these forces were the development of vertical and sub-vertical faulting systems at Craton-Sedimentary Basin contact and subsidence of overburden that appears to have also paved the way for the setting-up of the Ntem River bed and its flood plains. This river bed and its flood plains have been characterized as having a sedimentary deposit depth of 500 m and width of 20 km. Meanwhile, the deep-seated contact faulting systems within the two identified formations have varied fault magnitudes with a maximum of 60 km. The relatively high apparently resistivity values (up to1.0 kΩ•m) for the sedimentary and the very high values for the metamorphic formations (up to and above 10.0 kΩ•m) suggest that the whole area is at present relatively geo-tectonically stable.

关键词： Magnetotelluric Tectonics Intrusions Gravity-Gliding Upwelling Compression

Application of Rough Set, GSM and MSM to Analyze Learning Outcome—An Example of Introduction to Education

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Journal of Intelligent Learning Systems and Applications 2016年第1期8卷 23-38页

作者： Hui-Chung Ho Woody Jann-Der Fann Hsiu-Jye Chiang Phung-Tuyen Nguyen Duc-Hieu Pham Phuoc-Hai Nguyen Masatake Nagai Retired National Taichung University of Education Taiwan Ling-Tung University Taiwan National United University Taiwan Kien Giang teacher training college Rach Gia Vietnam Hanoi Pedagogical University 2 Xuan Hoa Vietnam Retired Teikyo University Tokyo Japan

Introduction to education is one of the basic courses in teacher education professional education, it covers a wide range of subjects. Thus, in order to practice the management teaching goals, the interdisciplinary developed mathematical tools are applied for the study. The participants of this study are students in course of introduction to education, and the research instruments applied are rough set, grey structural modeling (GSM), and matrix based-structural modeling (MSM). The purposes of this paper are: 1) To logically analyze educational datasets to practice the scientific traits in education;2) To benefit from directed hierarchical analysis to identify and propose action planning;3) To construct core-oriented educational structure as the criterion-reference for one-lesson-multiple-design and to provide the whole scope and visualized analysis with GSM and MSM.

关键词： Introduction to Education Rough Set GSM MSM One-Lesson-Multiple-Design

Investigation of the Antioxidant and UV Absorption Properties of 2-(2’-hydroxy-5’-methylphenyl)-benzotriazole and Its Ortho-Substituted Derivatives via DFT/TD-DFT

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Computational Chemistry 2021年第3期9卷 161-196页

作者： Numbonui Stanley Tasheh Aymard Didier Tamafo Fouegue Julius Numbonui Ghogomu Research Unit of Noxious Chemistry and Environmental Engineering Department of Chemistry Faculty of Science University of Dschang Dschang Cameroon Department of Chemistry Higher Teacher Training College Bertoua University of Ngaoundéré Bertoua Cameroon Department of Chemistry Faculty of Science The University of Bamenda Bamenda Cameroon

The demand and pursuit of chemical entities with UV filtration and antioxidant properties for enhanced photoprotection have been driven in recent times by acute exposure of humans to solar ultraviolet radiations. The structural, electronic, antioxidant and UV absorption properties of drometrizole (PBT) and designed ortho-substituted derivatives are reported via DFT and TD-DFT in the gas and aqueous phases. DFT and TD-DFT computations were performed at the M062x-D3Zero/6-311++G(d,p)//B97-3c and PBE0-D3(BJ)/def2-TZVP levels of theory respectively. Reaction enthalpies related to hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms were computed and compared with those of phenol. Results show that the presence of -NH2 substituent reduces the O-H bond dissociation enthalpy and ionization potential, while that of -CN increases the proton affinity. The HAT and SPLET mechanisms are the most plausible in the gas and aqueous phases respectively. The molecule with the -NH2 substituent (PBT1) was identified to be the compound with the highest antioxidant activity. The UV spectra of the studied compounds are characterized by two bands in the 280 - 400 nm regions. Results from this study provide a better comprehension antioxidant mechanism of drometrizole and present a new perspective for the design of electron-donor antioxidant molecules with enhanced antioxidant-photoprotective efficiencies for applications in commercial sunscreens.

关键词： Antioxidant Drometrizole Density Functional Theory Ultraviolet Absorption Hydrogen Atom Transfer Single Electron-Proton Transfer and Sequential Proton Loss Electron Transfer Mechanisms

3D Modelling from New and Existing Gravity Data of an Intrusive Body in the Northern Part of Kribi-Campo Sub-Basin in Cameroon

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International Journal of Geosciences 2017年第8期8卷 984-1003页

作者： Kue Petou Rokis Malquaire Owona Angue Marie Louise Njingti Nfor Manguelle-Dicoum Eliezer National Institute of Cartography Yaoundé Cameroon Postgraduate School of Sciences Technologies & Geosciences University of Yaoundé I Yaoundé Cameroon Department of Physics Advanced Teacher Training College University of Yaoundé I Yaoundé Cameroon Department of Physics Faculty of Science University of Yaoundé I Yaoundé Cameroon

A new gravity survey was carried out in the northern part of the onshore Kribi- Campo sub-basin in Cameroon. The data were incorporated to the existing ones and then analyzed and modeled in order to elucidate the subsurface structure of the area. The area is characterized in its north-western part by considerably high positive anomalies indicative of the presence of a dense intrusive body. We find, 1) from the analysis of the gravity residual anomaly map, the high positive anomalies observed are the signature of a shallow dense structure;2) from the multi-scale analysis of the maxima of the horizontal gradient, the structure is confined between depths of 0.5 km and 5 km;3) from the quantitative interpretation of residual anomalies by spectral analysis, the depth to the upper surface of the intrusive body is not uniform, the average depth of the bottom is h1 = 3.6 km and the depths to particular sections of the roof of the intrusion are h2 = 1.6 km and h3 = 0.5 km;4) and the 3D modeling gives results that are suggestive of the presence of contacts between rocks of different densities at different depths and a dense intrusive igneous body in the upper crust of the Kribi zone. From the 3D model the dense intrusive igneous block is surrounded by sedimentary formations to the south-west and metamorphic formations to the north-east. Both formations have a density of about 2.74 g/cm3. The near surface portions of this igneous block lie at a depth range of 0.5 km to 1.5 km while its lower surface has a depth range of 3.6 km to 5.2 km. The shape of the edges and the bottom of the intrusive body are suggestive of the fact that it forms part of a broader structure underlying the Kribi-Campo sub-basin with a great influence on the sedimentary cover.

关键词： Kribi-Campo Sub-Basin Gravity Data 3D Modelling Spectral Analysis Residual Anomaly