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Management of Peak Loads in an Emerging Electricity Market

Energy Engineering 2022年第6期119卷 2637-2654页

作者： Edwin N.Mbinkar Derek Ajesam Asoh Jerome Ndam Mungwe Livinus Songyuh Emmanuel Lamfu Laboratoire de Génie Electrique Mécatronique et Traitement du SignalENSPYUniversitéde YaoundéIYaoundeCameroun Department of Electrical and Electronic Engineering National Higher Polytechnic Institute(NAHPI)University of BamendaBamendaCameroon Department of Electrical and Power Engineering Higher Technical Teacher Training College(HTTTC)University of BamendaBamendaCameroon Mekin Hydroelectric Development Corporation MeyomessalaCameroon ENEO Cameroun S.A. DoualaCameroon

An electricity market is a trading platform provided by the actors in the electricity sector to sell and buy electricity while maintaining the stability of the transmission network and minimizing energy *** management of electrical energy for rational use consists of all the operations that the consumers can carry out in order to minimize their electricity bill,while the producers optimize their benefits and the transmission *** reduction of active and reactive power consumption and the smoothing of daily and yearly load profiles are the main objectives in this *** developed countries already have properly functioning electricity markets,but developing countries are still in their infancy of deregulated electricity *** major tools used in smoothing the load profiles include decentralized generation,energy storage and demand response.A load power smoothing control strategy is proposed to smooth the load power fluctuations of the distribution *** required power change is determined by evaluating the power fluctuation rate of the load,and then the required power change is allocated to some generators or to some stored ***,the consumers are made to curtail their power *** ideas proposed in this work provide important opportunities for energy policy makers and *** ideas would only be feasible if there exists real-time communication among the actors in the electricity *** results indicate that as much as 1100 Megawatt-hours of energy can be stored for smoothing the load profile,when applied to the Southern Interconnected Grid of the Cameroon power system;and that Time of Use(TOU)pricing could be used instead of rotating blackouts in case of energy shortage.

关键词： Peak load electricity markets decentralized generation energy storage demand response

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Effect of extrusion parameters on degradation of magnesium alloys for bioimplant applications:A review

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Transactions of Nonferrous Metals Society of China 2022年第9期32卷 2787-2813页

作者： Mahdi SHIRI Hassan JAFARI Raman SINGH Materials Engineering Department Faculty of Materials Engineering and Interdisciplinary SciencesShahid Rajaee Teacher Training University(SRTTU)16785-136 TehranIran Department of Mechanical&Aerospace Engineering and Department of Chemical Engineering 17 College Walk(Bldg 31)Monash University-Clayton Campus(Melbourne)Vic 3800Australia

Magnesium alloys,as a new generation temporary biomaterial,deserve the desirable biocompatibility and biodegradability,and also contribute to the repair of the damaged bone ***,they do not possess the required corrosion resistance in human body *** mechanical workings,such as extrusion,influence both the mechanical properties and bio-corrosion behavior of magnesium *** review aims to gather information on how the extrusion parameters(extrusion ratio and temperature)influence the bio-corrosion performances of magnesium *** effects are mainly ascribed to the alteration of extruded alloy microstructure,including final grain size and uniformity of grains,texture,and the size,distribution and volume fraction of the second *** recrystallization and grain refinement during extrusion provide a more homogeneous microstructure and cause the formation of basal texture,resulting in improved strength and corrosion resistance of magnesium *** temperature and extrusion ratio are reported as the influential factors in the *** reports reveal that the increase in extrusion ratio and/or the reduction in extrusion temperature cause a decrease in the final grain size,leading to intensification of basal texture,in parallel side of the samples with extrusion line,and to lower volume fraction and size of precipitates in magnesium *** all lead to improving the bio-corrosion resistance of the magnesium alloy implants.

关键词： magnesium alloys extrusion temperature extrusion ratio biodegradation microstructure

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Reducing Greenhouse Gas Emissions through Improving the Life Span of Wooden Power Electric Poles of Eucalyptus saligna

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Modern Mechanical Engineering 2022年第1期12卷 1-26页

作者： Joseph Voufo Zakari Yaou Florent Biyeme Rolland Djomi Richard Dadji Metangmo Théodore Tchotang National Advanced School of Engineering of Yaoundé (NASEY) Yaoundé Cameroon Laboratory of Civil and Mechanical Engineering Yaoundé Cameroon Higher Technical teacher training college of Ebolowa Ebolowa Cameroon Department of Industrial and Mechanical Engineering Yaoundé Cameroon

The present work deals with reducing greenhouse gas emissions through improving the life span of wooden power electric poles of Eucalyptus saligna. Indeed, in Sub-Saharan African countries, Cameroon in particular, most of the power line networks are made of wooden supports and according to the Cameroon energy distribution company, wooden poles represent 32% of the causes of death linked to the state of the network. The company’s 2019 annual report indicates that 40,000 wooden poles were in critical condition and should be replaced. A significant number of mechanical failures affecting these supports have been observed. For example, on the HVA/LV power line “D17 Nko- abang” in Yaoundé in Cameroon, less than three years old, 10 (ten) cases of poles falling and/or breaking, due to their mechanical loading, were observed over a period of fewer than nine months, causing an average service stoppage for more than 11 hours and affecting an average of 3280 customers. These incidents lead to questions about how the supports are dimensioned and what load capacities they are designed to support. The aim of this work is, therefore, to suggest a method of dimensioning wooden poles hence reducing green- house gas emissions due to the deforestation by reducing the number of woo- den poles at risk to be replaced on Cameroon’s electricity distribution network. And more specifically, to reduce the number of mechanical failures affecting the wooden supports observed by analyzing the current wooden supports with their loads and to make proposals for improving the actual dimensioning me- thods. From the study carried out, it appears that 449 out of 845 supports, i.e., 53% needed to be replaced or monitored because they support the nominal forces ranging from 85% to 150% of their admissible limit and proposals have been made to improve their dimensioning.

关键词： Electrical Power Line Dimensioning Wooden Pole Efforts on Pole Pole’s Height Method of Loading Overload Coefficients

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Enumeration of Stereoisomers of Chiral and Achiral Derivatives of Monocyclic Cycloalkanes Having Heteromorphous Alkyl Substituents with Distinct Length k

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Computational Chemistry 2019年第3期7卷 72-93页

作者： Alphonse Emadak Ibrahim Mbouombouo Ndassa Beauregard Thomas Makon Issofa Patouossa Robert Martin Nemba Laboratory of Applied Physical and Analytical Chemistry Department of Inorganic Chemistry Faculty of Sciences University of Yaounde 1 Yaounde Cameroon Laboratory of Chemistry Department of Chemistry High Teacher Training College University of Yaounde 1 Yaounde Cameroon

A combinatorial method based on the determination of the averaged weight of permutations controlling the chirality/achirality fittingness of 2n substitution sites of the monocyclic cycloalkane allows to obtain generalized functional equations for direct enumeration of enantiomers pairs and achiral skeletons of any derivatives of monocyclic cycloalkanes having heteromorphic alkyl substituents with the distinct length k with the empirical formula , wherein at least two alkyl groups??of the distinct size ?each. ?is the number of alkyl radicals ?of the system??verifying the relation . The integer sequences of enantiomer pairs and achiral skeletons are given for substituted derivatives of monocyclic cycloalkane for n = 3, 4 and k = 3, 4, 5. The composite stereoisomerism of this particular compound is also highlighted.

关键词： Enumeration Stereoisomer Chirality Achirality Monocyclic Cycloalkane Order of Alkyl Trees Polyalkylation

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Elaboration and Characterization of Composite Materials Reinforced by Papaya Trunk Fibers (Carica papaya) and Particles of the Hulls of the Kernels of the Winged Fruits (Canarium schweinfurthii) with Polyester Matrix

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Journal of Minerals and Materials Characterization and Engineering 2020年第5期8卷 341-352页

作者： Ze Eric Parfait Noah Pierre Marcel Nnomo Elobi Didine Nfor Clins Wiryikfu Betene Ebanda Fabien Ngahiyi Abbé Claude Valery Atangana Ateba Local Materials Promotion Authority Yaoundé Cameroon Department of Mechanical Engineering Higher Technical Teacher Training College Douala University of Douala Douala Cameroon Department of Industrial Construction Technology National Advanced School of Engineering of Douala University of Douala Douala Cameroon Laboratory of Civil Engineering and Mechanics Department of Mechanical Engineering National Advanced School of Engineering Yaoundé University of Yaoundé I Yaoundé Cameroon Mechanical Laboratory Higher Technical Teacher Training College Douala University of Douala Douala Cameroon

In this work we determine the physical and mechanical properties of local composites reinforced with papaya trunk fibers (FTP) on one hand and particles of the hulls of the kernels of the garlic (PCNFA) in the other hand. The samples are produced according to BSI 2782 standards;by combining fibers and untreated to polyester matrix following the contact molding method. We notice that the long fibers of papaya trunks improve the tensile/compression characteristics of composites by 45.44% compared to pure polyester;while the short fibers improve the flexural strength of composites by 62.30% compared to pure polyester. Furthermore, adding fibers decreases the density of the final composite material and the rate of water absorption increases with the size of the fibers. As regards composite materials with particle reinforcement from the cores of the winged fruits, the particle size (fine ≤ 800 μm and large ≤ 1.6 mm) has no influence on the Young’s modulus and on the rate of water absorption. On the other hand, fine particles improve the flexural strength of composite materials by 53.08% compared to pure polyester;fine particles increase the density by 19% compared to the density of pure polyester.

关键词： Physical and Mechanical Characterization Composite Fibers Papaya Tree Trunk Particles Shells Kernels Garlic Fruits

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Individual tree extraction from terrestrial laser scanning data via graph pathing

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Forest Ecosystems 2021年第4期8卷 903-913页

作者： Di Wang Xinlian Liang Gislain II Mofack Olivier Martin-Ducup Department of Remote Sensing Science and Technology School of Electronic EngineeringXidian University710077 Xi’anChina State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing Wuhan University430079 WuhanChina Department of Remote Sensing and Photogrammetry Finnish Geospatial Research Institute02430 MasalaFinland Plant Systematics and Ecology Laboratory Higher Teacher’s Training CollegeUniversity of Yaounde IBP 337 YaoundeCameroon AMAP Univ MontpellierIRDCNRSCIRADINRAEF-34000 MontpellierFrance

Background:Individual tree extraction from terrestrial laser scanning(TLS)data is a prerequisite for tree-scale estimations of forest biophysical *** task currently is undertaken through laborious and time-consuming manual assistance and quality *** study presents a new fully automatic approach to extract single trees from large-area TLS *** data-driven method operates exclusively on a point cloud graph by path finding,which makes our method computationally efficient and universally applicable to data from various forest ***:We demonstrated the proposed method on two openly available ***,we achieved state-of-the-art performance on locating single trees on a benchmark dataset by significantly improving the mean accuracy by over 10% especially for difficult forest ***,we successfully extracted 270 trees from one hectare temperate *** validation resulted in a mean Intersection over Union(mIoU)of 0.82 for single crown segmentation,which further led to a relative root mean square error(RMSE%)of 21.2% and 23.5% for crown area and tree volume estimations,***:Our method allows automated access to individual tree level information from TLS point *** proposed method is free from restricted assumptions of forest *** is also computationally efficient with an average processing time of several seconds for one million *** is expected and hoped that our method would contribute to TLS-enabled wide-area forest qualifications,ranging from stand volume and carbon stocks modelling to derivation of tree functional traits as part of the global ecosystem understanding.

关键词： Point cloud Segmentation Tree extraction Graph pathing

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Spatio-Temporal Assessment of Water Quality in Douala IV Municipality, Cameroon

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Journal of Water Resource and Protection 2019年第12期11卷 1441-1461页

作者： Mary Lum Fonteh Niba Theophile Fonkou Cornelius Mbifung Lambi Department of Geography Higher Teacher Training College The University of Bamenda Bambili Cameroon Department of Plant Biology Faculty of Science University of Dschang Dschang Cameroon Department of Geography Faculty of Social and Management Sciences University of Buea Buea Cameroon

The study analysed the spatial and temporal contamination levels of fresh water resources by saline intrusion in the Douala coastal area. Water samples were collected from 19 stations. 3 stations were selected from the mangrove area and 16 stations were selected from the rest of the area partitioned into four transects (coastal transect, inner transect 1, inner transect 2 and inner transect 3). Sampling was done repeatedly during the wet and dry seasons. They were analyzed for physico-chemical parameters according to the American Public Health Association methods. Geostatistical analysis was used in mapping the water properties. Considerable levels of actual electrical conductivity values (208.91 to 660.63 and 45 to 7540 μS/cm for the wet and dry seasons, respectively);calcium (0.06 to 85 and 4 to 256 mg/L for the wet and dry seasons, respectively);sulphate (0 to 103 and 0 to 99 mg/L for the wet and dry seasons) and total dissolved solids (15.79 to 1467 and 20 to 3750 mg/L for the wet and dry seasons, respectively) were observed for ground water in the study area based on spatio-temporal assessment. From the output grid, it could be deduced that the south eastern region had a hint of salt water intrusion (SWI) contamination of fresh water resources with actual value highs of electrical conductivity (1790 and 820 μS/cm) for the dry and wet seasons, respectively. Calcium highs (140 and 16 mg/L) for the dry and wet seasons were obtained at the central part of the study area. The spatial distribution of calcium highs extends from the central zone of the study area in the dry season and the south eastern zone in the wet season. The southern region is more vulnerable to contamination by calcium ions during this season. An up to date scope for surveillance monitoring and forecasting regarding the deterioration of coastal aquifers is recommended. Modelling of aquifers shifts for the coastal zone should be instituted as a means of ensuring efficient fresh water resources eva

关键词： Spatio-Temporal Assessment Fresh Water Resources Water Quality Geostatistics Douala IV Municipality Cameroon

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Determination of the Structural Lineaments in the Kribi-Campo-Ma’an Area from a Multi-Scale Analysis of Gravity Data Using the HGM and Euler 3D Deconvolution Approaches

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International Journal of Geosciences 2016年第9期7卷 1122-1143页

作者： Owona Angue Marie Louise Clotilde Assembe Stephane Patrick Njingti Nfor Ngoh Jean Daniel Ndougsa Mbarga Theophile Kue Petou Rokis Bisso Dieudonné Department of Physics Advanced Teacher Training College University of Yaoundé I Yaoundé Cameroon Postgraduate School of Sciences Technologies & Geosciences University of Yaoundé I Yaoundé Cameroon Department of Physics Faculty of Science University of Bamenda Bambili Cameroon

With the aim to produce a detailed structural map and then enhance the geological information of the south-western Cameroon, a field gravity study is carried out in the Kribi-Campo-Ma’an area (SW Cameroon). This study area is assumed to undergo pending active tectonics as witnessed by several earthquakes [1]. Besides, the area has been affected by some shears that gave rise to many major faults including the Kribi-Campo Fault (KCF). This N-S lineament is an active fault corresponding to the NW margin of the CC [2] [3] and related to the development of the Kribi-Campo basin. The gravity data analysis enables to highlight many deeply-seated structural features trending in the NE, NNE, N-S, NNW, NW and E-W directions in this region. The NW-SE trend is more strongly developed than the other identified trends and could have deeply affected the major NNE structure. The NNE-SSW to N-S fractures and faults which are local relays of the Kribi-Campo fault are related to the Kribi shear zone. The fairly good clustering observed on local maxima of the horizontal gradient magnitude enables to suggest that the contacts outlined have vertical to subvertical dips. However, a probable interpretation of these features is that they are vertical to subvertical faults which follow the aforementioned directions. The location of the study area in the gulf of Guinea suggests that it sustains tectonics related both to the equatorial and the south Atlantic oceans opening.

关键词： Gravity Anomaly Lineament Kribi-Campo Fault Dip

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Evidences by Multiscale Analysis and 2D3/4 Models from the Magnetic Anomalies and Iron Mineralization (BIF) over the DJADOM-ETA Area, Southeastern Cameroon

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Open Journal of Earthquake Research 2020年第1期9卷 19-32页

作者： Justine Yandjimain Théophile Ndougsa-Mbarga Arsène Meying Paul Claude Ngoumou Postgraduate School of Sciences Technologies & Geosciences University of Yaoundé I Yaoundé Cameroon Department of Physics Advanced Teacher’s Training College University of Yaoundé I Yaoundé Cameroon Department of Applied Geophysics Geology and Mining Exploitation College University of Ngaoundéré Ngaoundéré Cameroon

The Magnetic method is one of the best geophysical techniques used to delineate subsurface structures. This study was conducted to investigate the basement faulting and ore mineralization into the overlying geological cover. The GEOSOFT v8.4 software was used to process the data. Upward continuation of the residual magnetic intensity map at various altitudes and the maxima of their horizontal gradient magnetic were used to highlight faults from shallow to deep, as well as, their dips and mineralization zones. The faults with the directions E-W, ESE-WNW and ENE-WSW are identified confirming the result of [1]. This study also reveals that, the layer is affected by faults propagating from the basement upwards into the cover. Our results added additional information to the knowledge of the geological structure and the mineral resources potential in the study area. Based on the 2D3/4 modeling, the Dja Fault (DF) is revealed and highlighted sub-area marked by a magnetite/or hematite dolerite, schist and sandstone blocks, which show strong magnetization. Specifically, in this area, models are made of BIF (bounded iron formation) and BIQ (bounded iron quartzite) as dominant minerals.

关键词： Aeromagnetic Anomalies Multiscale Mineralization (BIF (Bounded Iron Formation) BIQ (Bounded Iron Quartzite)) HMG (Horizontal Gradient Magnetic) Faults

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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

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