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Optimum insulation thickness and exergy savings of building walls in Bamenda: a comparative analysis

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Energy Storage and Saving 2024年第1期3卷 60-70页

作者： Fodoup Cyrille Vincelas Fohagui Yemeli Wenceslas Kohole Njimboh Henry Alombah Derek Ajesam Asoh Ghislain Tchuen Department of Electrical and Electronics Engineering College of TechnologyThe University of BamendaP.O.Box 39BambiliCameroon Department of Energetic Environment and Thermal EngineeringIUT-FV BandjounUR-ISIEUniversity of DschangP.O.Box 134BandjounCameroon National higher Polytechnic Institute and higher technical teacher training college The University of BamendaP.O.Box 39BambiliCameroon

The goal of this study is to examine the energetic,entransy,and exergetic methodologies employed to estimate the ideal insulation thickness for construction walls in terms of cost and ecological *** achieve these goals,the life cycle cost analysis-based insulating thicknesses of the various methods are evaluated along with the overall costs,yearly cost reductions,and total *** fuel consumption,CO_(2) emissions,and ecological effects are then compared using an environmental analysis based on the three *** savings of hollow concrete brick(HCB),compressed stabilized earth brick(CSEB),and sundried earth brick(SEB)walls are evaluated along with the insulation thicknesses in terms of cost and ecological *** a result,it is determined that the exergetic technique is better suited for optimizing insulating *** CSEB,SEB,and HCB walls,the economic ideal insulation thicknesses are 0.01 m,0.016 m,and 0.02 m,with yearly financial savings of 5$⋅m^(-2),7.5$⋅m^(-2),and 9$⋅m^(-2).For CSEB,SEB,and HCB walls,accordingly,the ecological optimal insulation thicknesses are 0.023 m,0.032 m,and 0.040 m,with net savings of exergetic ecological impact equal to 59 mPts⋅m^(-2),55 mPts⋅m^(-2),and 51 mPts⋅m^(-2).

关键词： Insulation thickness Environmental impact Entransy Exergy Exergoeconomic

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

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

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

Total Fat, Fatty Acid Composition, Tocopherol and Tocotrienol Profiles in Fermented Beans of Ten Controlled Pollinated Cocoa (Theobroma cacao L.) Hybrids from Cameroon

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American Journal of Plant Sciences 2024年第5期15卷 359-373页

作者： Martin Paul Arnaud Mbida Simon Perrez Akoa Ronelle Fabiola Mbia Manga Ndjaga Jude Martine Louise Ondobo Onomo Pierre Effa Department of Biochemistry Faculty of Science University of Yaounde I Yaounde Cameroon Laboratory of Plant Physiology and Biochemistry Department of Biological Science Higher Teacher&#8217s Training College University of Yaounde I Yaounde Cameroon Department of Food Science and Technology Faculty of Agriculture and Veterinary Medecine University of Buea Buea Cameroon National Technology Development Committee Ministry of Scientific Research and Innovation Administrative Center Yaounde Cameroon Department of Agriculture and Agropastoral Higher Technical Teacher&#8217s Training College University of Ebolowa Ebolowa Cameroon

This study aimed to discriminate ten Cameroonian cocoa hybrids according to their total fat, fatty acid composition, tocopherol and tocotrienol profiles. Six cocoa clones from the gene banks of the Cameroon Cocoa Development Corporation were used to create hybrids. The determination of fatty acid composition was carried out by using a gas chromatography (GC) apparatus coupled by a flame ion detector (FID). Tocopherol and tocotrienol analysis was performed by upper high-performance liquid chromatography (UHPLC). Information on the impact of the genotype on the cocoa fat composition was provided. The major fatty acids (FA) in fermented samples are stearic (34.57%), palmitic (26.13%), oleic (34.13%) and linoleic (3.16%) acids. (35.05% to 35.6%). SCA12 × ICS40, SCA12 × SNK13, SNK13 × T79/501 have the least hard cocoa butters. Tocopherols analysis showed a predominance of γ-tocopherols (94.64 ± 1.51 to 292.16 ± 3.17 µg∙g−1), whereas only a small amount of β and δ-tocopherol (from 0.46 to 2.78 µg∙g−1 and 0.12 to 5.82 respectively) was observed. No γ-tocotrienol was found in fermented samples. A differentiation in terms of total fat and tocopherol content was observed amongst hybrids with the same mother-clone, suggesting an impact of pollen on these compounds.

关键词： Cocoa Hybrids Lipid Composition UHPLC GC-FID

Numerical Study of the Vibrations of Beams with Variable Stiffness under Impulsive or Harmonic Loading

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World Journal of Engineering and Technology 2024年第2期12卷 401-425页

作者： Moussa Sali Fabien Kenmogne Jean Bertin Nkibeu Abdou Njifenjou Laboratory of Materials Mechanics and Civil Engineering National Higher Polytechnic School of Maroua University of Maroua Maroua Cameroon Department of Civil Engineering Advanced Teachers Training College of the Technical Education University of Douala Douala Cameroon Laboratory Engineering Civil and Mechanics National Advanced School of Engineering University of Yaound&#233 1 Yaound&#233 Cameroon Laboratory of Energy Materials Modeling and Method (E3M) National Advanced School of Engineering University of Douala Douala Cameroon Laboratory of Mathematical Engineering and Information Systems National Advanced School of Engineering University of Yaound&#233 1 Yaound&#233 Cameroon

The behavior of beams with variable stiffness subjected to the action of variable loadings (impulse or harmonic) is analyzed in this paper using the successive approximation method. This successive approximation method is a technique for numerical integration of partial differential equations involving both the space and time, with well-known initial conditions on time and boundary conditions on the space. This technique, although having been applied to beams with constant stiffness, is new for the case of beams with variable stiffness, and it aims to use a quadratic parabola (in time) to approximate the solutions of the differential equations of dynamics. The spatial part is studied using the successive approximation method of the partial differential equations obtained, in order to transform them into a system of time-dependent ordinary differential equations. Thus, the integration algorithm using this technique is established and applied to examples of beams with variable stiffness, under variable loading, and with the different cases of supports chosen in the literature. We have thus calculated the cases of beams with constant or variable rigidity with articulated or embedded supports, subjected to the action of an instantaneous impulse and harmonic loads distributed over its entire length. In order to justify the robustness of the successive approximation method considered in this work, an example of an articulated beam with constant stiffness subjected to a distributed harmonic load was calculated analytically, and the results obtained compared to those found numerically for various steps (spatial h and temporal τ ¯ ) of calculus, and the difference between the values obtained by the two methods was small. For example for ( h=1/8 , τ ¯ =1/ 64 ), the difference between these values is 17%.

关键词： Successive Approximations Method Direct Integration Differential Equations Beams of Variable Stiffness Quadratic Parabola Impulse and Harmonic Loads

Glycine-nitrate auto-combustion synthesis and magnetic properties of nanocrystalline NdAl_(x)Fe_(1-x)O_(3) perovskites

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Journal of Rare Earths 2023年第1期41卷 108-115页

作者： E.A.Nforna HJ.M.Ngantchou J.N.Ghogomu Department of Fundamental Science Higher Technical Teacher Training CollegeUniversity of BamendaP.O.Box 39BambiliCameroon Department of Chemistry Faculty of SciencesUniversity of DoualaP.O.Box 24157DoualaCameroon Department of Chemistry The University of BamendaP.O.Box 39BambiliCameroon Department of Chemistry University of DschangP.O.Box 67DschangCameroon

The effect of substitution of Fe^(3+) by Al^(3+) on the structure and magnetic properties of NdAl_(x)Fe_(1-x)O_(3) perovskite nano-powders(x=0.0,0.1,0.2,0.3,0.4,and 0.5) prepared by the glycine-nitrate auto-combustion method was *** samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),and energy dispersive X-ray spectroscopy(EDX).The magnetic properties of the samples were investigated using a vibrating sample magnetometer(VSM).The X-ray results for all samples reveal the formation of an orthorhombic perovskite phase(space group Pbnm) with no secondary *** crystallite sizes of the nanoparticles are found to decrease with increasing Al content,and are in the range of 53-38 *** images show spherical nanoparticles with *** FT-IR spectra confirm the presence of metal oxygen *** M-H loop of the pristine NdFeO_(3) sample is antiferromagnetic in the a b plane with weak ferromagnetism in the *** AI inclusions in the pristine polycrystal thereby creating magnetic vacancies is seen to influence the magnetic *** magnetic dilution results in enhanced magnetisation at low Al content;x=0.1,0.2(saturation magnetisation being 2.08 and 2.05 emu/g,respectively) compared to the pristine sample with a saturation magnetisation of 1.43 emu/g due to increased exchange *** dilution with nonmagnetic dopant induces the phase transition from weak ferromagnetic to paramagnetic depending on the impurity *** coercive field for NdFeO_(3) is found to be equal to 1950 Oe and decreases with *** findings lay a ground work for research in tuning magnetic properties and in spintronics with potential applications in data storage,switches and electronic devices.

关键词： Anti-ferromagnetism Weak ferromagnetism Orthorhombic NdAl_(x)Fe_(1-x)O_(3) Perovskite nanopowders Magnetic dilution

Evolution of Floristic Composition and Structural Parameters between Two Management Inventories in a Tropical Forest in the East Cameroon Region

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Open Journal of Forestry 2023年第3期13卷 243-261页

作者： Aichetou Ngoungoure Manjeli Fridolin Choula Kadiri Serge Bobo Achille Bernard Biwole Mireille Feudjio Department of Forestry Faculty of Agronomy and agronomical Sciences University of Dschang Dschang Cameroon Department of Biology Higher Teacher Training College The University of Bamenda Bambili Cameroon Department of Forestry Higher Teacher Technical Training College The University of Douala Douala Cameroon

The realization of two management inventories in 2003 and 2020 on the same forest concession made it possible to characterize the floristic composition and to describe some structural parameters on three sites established according to the period of exploitation. Due to the change in the orientation of the lines, it was noted that respectively 82 and 85 species from the first inventory are not found in the second and inversely. A total of 311 species were identified in 2003, compared to 314 in 2020. The density varies from 111 to 140 stems/ha for all the individuals, 19 to 25 for the main species and 15 to 20 for the most exploited species. The decrease in the basal area between the two phases of 12% for all the species and 13% for the main species on the site exploited before the first inventory indicates a persistence of the disturbance for years after logging. It is proposed to supplement the management plans decisions with annual measures based on more complete inventories and to ensure the application of reduced impact logging measures.

关键词： Tropical Forest Floristic Composition Density Basal Area

Effects of Soil Compaction in the Fight against Unpaved Roads Degradation Due to Erosion Caused by Heavy Rain: Proposition of a Specific CBR Evaluation Model

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Engineering（科研） 2021年第3期13卷 95-104页

作者： Timothée Thierry Odi Enyegue Eric Flavien Mbiakouo-Djomo Hugues Tsanga Fabien Kenmogne Blaise Ngwem Bayiha Gilbert Tchemou Ebenezer Njeugna Didier Fokwa Laboratory of Mechanics Doctorate Unit of Engineering Sciences Doctorate School of Fundamental and Applied Sciences University of Douala Douala Cameroon Department of Rural Engeineering FASA University of Dschang Dschang Cameroon Civil Engineering Department Higher Technical Teacher’s Training College University oh Douala Douala Cameroon Mechanics Engineering Department Higher Technical Teacher’s Training College University oh Douala Douala Cameroon

Unpailt roads are generally subject to erosion, when they need to be bitumen, civil engineers need to know the geotechnical capabilities of the soil layers to be used as support, among these capabilities, for example, soil characteristics to withstand erosion. CBR has often been used to classify these soils according to their compaction. In this article, we propose a correlation between CBR and eroded soil mass through a simulator. Indeed, in this article we show that using a simulator, soils can be classified according to their ability to withstand water erosion, whether internal or external. Indeed it is shown that the mass of eroded soil is related to the compaction capacity of the soil just as the CBR also has. We study the effects and influence of soil compaction on the ability of an unpaved road to resist erosion caused by falling raindrops. To do this, lateritic soil is submitted to different compaction pressures. The compacted soil is then submitted to CBR test and rain fall through a mini rain simulator. Correlations between eroded soil masse and compaction pressure as well as CBR are derived. The study shows that the compaction reduces the erodibility and increases the bearing capacity of soil. The formula obtained is significant because we have a new way of evaluating soils in the laboratory.

关键词： Compaction Erosion Lateritic Soil Rain Drop Unpaved Roads

Characterisation of Early Age Deformations in Cement Paste: Case of Chemical and Autogenous Shrinkage

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Journal of Minerals and Materials Characterization and Engineering 2020年第4期8卷 223-239页

作者： Nkwenti Flavious Tanue Tubuo Fabian Fokwa Didier Tchemou Gilbert university of douala Post Graduate Training Unit for Engineering Sciences Douala Cameroon university of douala Higher Technical Teachers’ Training College Douala Cameroon

Concrete is commonly seen as a durable and long-lasting construction material. However, the long-term performance of a concrete structure can be greatly compromised by early-age cracking. This work is an experimental contribution to study early age deformations of cement paste. Its aim is, firstly, to develop an experimental dispositive for assessing chemical and autogenous shrinkage, and secondly, to measure these volumetric deformations in cement paste. The setup was done following the gravimetric method of measurement, which exploits the Archimedes’ principle. It is made up of an electronic balance, a data accusation unit, a temperature control unit and a buoyancy bath. Investigations were done on Portland cement (CPA-CEM II) at the following W/C ratios: 0.25, 0.3, 0.35, 0.4 and 0.5. It was noticed that the water-cement ratio does not influence the magnitude of the chemical shrinkage in a significant manner but had a kinetic effect;a lower W/C induces a faster rate of chemical shrinkage. Autogenous shrinkage was discovered to be highly inversely proportional to the W/C and was also noticed to be in a function of chemical shrinkage within the first 2 to 4 hours when the paste was still liquid.

关键词： Autogenous Shrinkage Chemical Shrinkage Volumetric Deformation Water-Cement Ratio

Forecast for the Cameroon’s Residential Electricity Demand Based on the Multilinear Regression Model

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Energy and Power Engineering 2020年第5期12卷 182-192页

作者： Serge Guefano Jean Gaston Tamba Louis Monkam Beguide Bonoma Institute of Technology University of Douala Douala Cameroon higher teacher training college University of Yaoundé I Yaoundé Cameroon

The electricity needs of populations in Cameroon are increasing and are still very inadequate. Companies, public buildings and households are facing frequent blackout which constrain development and social well-being. Therefore, the present work tried to forecast the electricity demand in the residential sector in Cameroon, in order to contribute significantly to the mastery of electricity consumption and highlight decision-makers in this sector. Six macroeconomics parameters covering the period 1994-2014 are used for these issues. Stationarity tests within gross domestic product, gross domestic product per capita, electricity consumption, population and numbers of subscribers and households respectively;reveal that all the series are I(1). Thus, the VAR (Vector Autoregressive) model has been retained to forecast the electricity demand until 2020. The cusum test and the cusum of squared test attest the stability of that model with a margin of error of 0.02%. Previsions are then more reliable and show that the electric request will skip from 1721 GWh in 2014 to more than 2481 GWh in 2020 approximatively, following a growing yearly rate of 5.36%. In order to reach its emergence, Cameroon ought to speed up its production in the domain of hydroelectric and thermal grid in order to meet the requirements in electric power in short and long term.

关键词： Modeling of the Electricity Demand Forecast Residential Sector VAR Model Cameroon