The use of plastics from petrochemical resources poses environmental impacts, and one of the alternative solutions is the use of starch. The objective of this present work has been to present the literature on starch,...The use of plastics from petrochemical resources poses environmental impacts, and one of the alternative solutions is the use of starch. The objective of this present work has been to present the literature on starch, and to highlight the debate in the development of composite films. The approach adopted was to present the state of the art on starch and thermoplastic starch matrix composites. The work shows that starch is available worldwide and can be used in the manufacture of biodegradable plastics;the debate remains on the reinforcement of thermoplastic starch to improve its physical and mechanical properties poor;then researchers must diversify the reinforcements to see the impact on the properties of thermoplastic starch.展开更多
This work is part of the resolution of problems encountered on a 225 KV MANGOMBE-OYOMABANG line. This line is characterized by important technical losses, so that the voltage injected in the busbar is always lower tha...This work is part of the resolution of problems encountered on a 225 KV MANGOMBE-OYOMABANG line. This line is characterized by important technical losses, so that the voltage injected in the busbar is always lower than 200kV. The main objective of this work is to show the new solutions that can provide a combined FACTS-STATCOM and IPC 240 dual system on this line. Then to show the limitation of STATCOM compared to RPI 240. The results obtained allowed us to observe that in symmetrical operation the STATCOM improves the voltage profile on the busbar and in asymmetrical operation we found that it continues to regulate the voltage of each phase despite the unbalance. But the system remains too unbalanced because of the sequence current flow. The IPC 240 corrects this limitation, allowing asymmetrical operation of the line in an emergency while providing continuous service to the load.展开更多
This article systematically delves into a comprehensive analysis of the latest and most advanced techniques for the assessment of slope stability. It particularly focuses on strategies aimed at enhancing slope stabili...This article systematically delves into a comprehensive analysis of the latest and most advanced techniques for the assessment of slope stability. It particularly focuses on strategies aimed at enhancing slope stability in road construction. In addition to this analysis, the article presents an illustrative case study centered on the Toffo-Lalo Road Project. The core objective of this paper is to scrutinize the stability of large embankments in road construction, with a specific emphasis on the development and asphalt overlay of the Toffo-Lalo road. This scrutiny is conducted through the utilization of stability calculation software, GEOSTUDIO2018, specifically its SLOPE/W module. Within this framework, a detailed model of the cutbank located at KP1+750-2+250 was meticulously developed. This model takes into account the physical-mechanical characteristics of the soil at the site, as well as the topographic layout. Its attributes include a cohesion value of 11.3 Kpa, a density of 16.57 KN/m<sup>3</sup>, and a friction angle of 27˚. The modeling results, employing the Morgenstern-Price method—an approach renowned for its adherence to equilibrium conditions and provision of precise results—conclude that the safety coefficient (Fs = 1.429) prior to any reinforcement signifies a critical state of slope stability. To address this, the article explores the implementation of reinforcement techniques, particularly focusing on rigid inclusions like nailing and piles. The modeling exercises reveal a noteworthy enhancement in the safety coefficient (Fs) post-reinforcement. Furthermore, the article undertakes a parametric study to optimize the reinforcement strategies. This analysis highlights that anchoring at 0˚ downward relative to the horizontal plane and employing a pile angle of 90˚ represent the most favorable approaches. These measures yield safety coefficients of 3.60 and 2.34, respectively, indicating substantially improved slope stability.展开更多
Lima bean is a tropical and subtropical legume from the genus Phaseolus which is cultivated for its importance in food and in medicine, but which remains a Neglected and Underutilized Crop in Benin. Understanding the ...Lima bean is a tropical and subtropical legume from the genus Phaseolus which is cultivated for its importance in food and in medicine, but which remains a Neglected and Underutilized Crop in Benin. Understanding the genetic diversity of a species’ genetic resources is useful for the establishment of appropriate conservation strategies and breeding programs and for sustainable use. We use 6 out of ten SSR markers to analyze the diversity and population structure of 28 Lima bean landraces collected in Benin. A total of 28 alleles with an average of 4.16 alleles per SSR were amplified. The Polymorphic Information Content value ranged from 0.079 to 0.680 with an average of 0.408. The analysis of population structure revealed three subpopulations. PCoA revealed three well-separated clusters among the analyzed accessions in accordance with the population structure results and the clustering based on the Neighbor-Joining tree. AMOVA showed highly significant (p = 0.001) diversity among and within populations. Hence, 32% of the genetic variation was distributed among the population and 68% was distributed within populations. A high PhiP value (0.321) was found between the three sub-subpopulations indicating a high genetic differentiation between these sub-subpopulations. By exhibiting the highest average number of alleles, Shannon-Weaver information and Shannon-Weaver diversity indices, and the highest mean number of private alleles, subpopulation 1 is the main gene pool of the analyzed collection. The present study is an important starting point for the establishment of appropriate conservation strategies and breeding programs for Lima bean genetic resources.展开更多
The aim of this work was to propose a possibility of using plastic aggregates from waste to reduce the shrinkage and expansion observed in concrete. The process of obtaining plastic aggregates was presented. Natural a...The aim of this work was to propose a possibility of using plastic aggregates from waste to reduce the shrinkage and expansion observed in concrete. The process of obtaining plastic aggregates was presented. Natural aggregates were partially substituted by plastic aggregates in the percentages: 0%, 5%, 10%, 20% and 30%. Drying shrinkage, water absorption and expansion tests were carried out on three families of concrete: control concrete (BT), concrete with addition of BAgP-PEHD high-density polyethylene plastic aggregate and with polyvinyl chloride BAgP-PVC. Given the slow appearance of the internal sulfate attack (ISA), an experimental technique was proposed to accelerate the appearance of this pathology. This technique involves heat treatment which stimulates the heating of the concrete at a young age, followed by a cycle of drying and cooling and ends with total immersion in water. The method of measuring expansions through sample image correlation was also proposed. The results showed an increased skrinkage of BAgP-HDPE compared to BT. On the other hand, a significant decrease in shrinkage was observed in BAgP-PVC samples. Water absorption increased in BAgP-HDPE and BAgP-PVC compared to BT. Greater expansion was observed at the cement paste-plastic aggregate interface than at the cement paste-natural aggregate interface. Given these properties, BAgP-PVC can be recommended for paving surfaces exposed to the hard weather conditions.展开更多
Structures erected on swelling clay soils are subjected to several stresses which are at the origin of the premature deterioration of the infrastructures. The soils being supports for the works, the improvement of the...Structures erected on swelling clay soils are subjected to several stresses which are at the origin of the premature deterioration of the infrastructures. The soils being supports for the works, the improvement of their weak characteristics with cotton fibers will not only increase the bearing capacities of these soils and the resolution of the environmental problem, by eliminating the CO<sub>2</sub> produced by the burning of the stems after harvest. The objective of this study is to contribute to the improvement of the characteristics by cotton stalk powder of the swelling clay soils used as the foundation of the infrastructures in order to guarantee their durability. Identification and mechanical parameterization tests were carried out on raw soil samples taken at 1.5 meters deep and on samples improved with cotton stalk powder at different levels (3%, 6% and 10%). The results from the physical tests reveal that the soil studied is very plastic silt. As for the mechanical tests, it appears that by adding 3% cotton stalk powder to dry density which goes from 1.435 t/m<sup>3</sup> compared to the control sample with a dry density of 1.50 t/m<sup>3</sup>;which reflects an improvement in the compaction characteristics of the soil studied. The dry densities are 1.445 t/m<sup>3</sup> and 1.29 t/m<sup>3</sup> for the samples improved with 6% and 10% cotton stalk powder.展开更多
This comprehensive review paper explores various aspects of geotechnical engineering, with a focus on the management of unstable terrains, numerical methods for solving complex soil and consolidation problems, rheolog...This comprehensive review paper explores various aspects of geotechnical engineering, with a focus on the management of unstable terrains, numerical methods for solving complex soil and consolidation problems, rheological analysis of suspensions and muddy soils, and stability analysis of slopes. It begins by examining the unique physicochemical properties of cohesive sediments, including cohesion and specific surface area. The temporal evolution of deposit concentration and average bed concentration in unstable terrains is discussed, along with settling behavior of isolated particles and hindered settling using empirical equations. Key sedimentation theories, such as Kynch’s theory, and geotechnical consolidation theories, including Terzaghi’s consolidation equation and Gibson’s theory, are presented. The investigation interrelates these theories and principles to offer a holistic view of managing unstable terrains. It also addresses the challenges associated with experimental determination of constitutive relationships and presents alternative simplification methods proposed by researchers. Additionally, it delves into numerical methods for solving nonlinear partial differential equations governing soil behavior, emphasizing the need for numerical frameworks and discussing various techniques and associated challenges. The rheological analysis section covers material flow behavior, rheological behavior models, and the rheological properties of water and cohesive sediment mixtures. Fundamental geotechnical calculations, constitutive laws, and failure criteria are explained, highlighting their relevance in geotechnical engineering applications. This paper provides a multidimensional perspective on geotechnical engineering, offering valuable insights into soil properties, consolidation processes, numerical methods, rheological analysis, and slope stability assessment for professionals in the field.展开更多
This document presents a study of the behaviour of a pavement structure on compressible soil and the evaluation of its durability. The objective of this study is to highlight the impact of taking into account the non-...This document presents a study of the behaviour of a pavement structure on compressible soil and the evaluation of its durability. The objective of this study is to highlight the impact of taking into account the non-linear elastic behaviour of soils and granular materials in the design process. To this end, a numerical modelling of the pavement of the beau-rivage-Djassin crossroads section in Porto-Novo was carried out, based on a compressible soil whose behaviour will be considered elastoplastic. The subgrade soil on the section is made up of several sub-layers. The layer of soft, highly plastic clay was modelled according to a modified Cam Clay behaviour, a model of swelling clay soils. The fine sand layer and the granular layers of the structure are modelled according to Mohr-Coulomb behaviour. The loading is considered to be uniformly distributed according to the assumptions of the Burmister model in the French standard. A first verification with ALIZE allowed to validate the structure on the basis of the rutting deformation at the head of the platform ε<sub>z</sub> = 359.6*10<sup>-6</sup> which remains lower than the admissible deformation ε<sub>z</sub><sub>,adm</sub> = 360*10<sup>-6</sup>. The numerical calculation was carried out using the finite element method, the code of which is implemented under the PLAXIS v21 software. A comparative study with the results of the ALIZE design revealed that the numerically calculated strains ε<sub>z</sub> = 585*10<sup>-6</sup> are higher than those of ALIZE. These numerical strains, which are higher than the elastic strains, do not meet the validation criteria that the strains under loading must remain below the allowable strains. An evaluation of the pavement durability was carried out and it was found that the pavement would only last under traffic for 3 years before the first fatigue deformations appeared.展开更多
This work focuses on the valorization of local materials.The rock that is granite,a material used in construction thanks to its mechanical resistance,is the subject of our study.The granite of the commune of Savè...This work focuses on the valorization of local materials.The rock that is granite,a material used in construction thanks to its mechanical resistance,is the subject of our study.The granite of the commune of Savè,made it possible to appreciate the thermal behavior of this rock studied with a view to its use as a building material.To this end,a thermal diffusivity measurement test was carried out on this material.Thus,we made samples which were then connected to a data acquisition box via thermocouples.A Python script is used to ensure the collection of temperature values over time.From this thermal diffusivity test carried out on the granite taken from the Savèbreasts,we obtained an average diffusivity a=5.84×10^(-6)m^(2)/s.As a result,the thermal effusivity and the heat capacity of the material were determined having respectively the value 1,351.09 J/(K·m^(2)·s^(1/2))and 547,945.21 J/(m^(3)·K).These different results highlight a thermal characterization of Savègranites as a relevant material in the design and construction of an energy-efficient eco-housing.展开更多
The importance of slope stability in civil engineering cannot be underestimated, as failure of these structures can result in significant damage to downstream infrastructure and property. In this study, we used the Bi...The importance of slope stability in civil engineering cannot be underestimated, as failure of these structures can result in significant damage to downstream infrastructure and property. In this study, we used the Bishop slice method, combining both an analytical approach and a numerical approach using the SLOPE/W module of the Geostudio 2018 R2 software. The results obtained from these two methods showed that increasing soil cohesion helps to improve slope stability. The safety coefficients obtained by the analytical method vary between 0.621 and 1.422, while those obtained by the numerical method vary between 0.622 and 1.447, for cohesion values ranging from 4 kPa to 20 kPa. The results obtained by these two methods show a linear relationship between the safety coefficients and soil cohesion. The equation of the analytical method is y = 0.0496x + 0.4407, while that of the numerical method is y = 0.0512x + 0.4357. The results of the analytical approach indicate that a safety coefficient of 1.5 is reached when the cohesion reaches a value of 22 kPa, while the numerical approach shows a safety coefficient of 1.5 reached at a cohesion of 21 kPa. The difference between these two cohesion values can be explained by the number of slices used, which is smaller in the analytical method. However, the equation derived from the analytical method can be used as a general guide to assess the evolution of the safety coefficient of an overloaded slope in long-term behaviour with an increase in cohesion. However, it is important to stress the importance of verification using specialised software based on the finite element method.展开更多
This work focuses on the design of a new type of eco-material based on Typha“Domingensis”and clay from the south of the Republic of Benin through various dosages.Three particle size classes of typha shavings were se...This work focuses on the design of a new type of eco-material based on Typha“Domingensis”and clay from the south of the Republic of Benin through various dosages.Three particle size classes of typha shavings were selected to be mixed with two types of clayin order to make parallelepiped shaped samples ready for experimentation.The massive use of these briquettes thus obtained,in the construction of habitats,would not only contribute to reducing the energy consumption inside the dwellings but also would limit the invasion of the waterways of Benin,which would facilitate navigation,fishing and river sanitation activities.In addition,this biosourced,low-polluting material would contribute to improving the energy transition by integrating it into rehabilitation of buildings.展开更多
The rapid economic growth of the town present the matter of water issue as a problem to human life human life, construction life, agriculture, etc. This study is to predict techniques of foundation construction throug...The rapid economic growth of the town present the matter of water issue as a problem to human life human life, construction life, agriculture, etc. This study is to predict techniques of foundation construction through the displaying of the water table at the flow direction in the town of Kumba and GIS. It is characterized by a significant research question which is the level of fall and rise in groundwater levels within the town of Kumba and this influence on choice of types of foundation in construction. This study is directed to decision makers, and technicians of the construction field to develop policies facilitating the supervision when building construction foundation by informing about water level depth and its flow direction in the town. To achieve this, depths of static water levels were measured in over 200 randomly selected hand-dug wells in Kumba, after their geolocation and data were collected during the dry season (November and March 2017) and during the rainy season (between April and October 2017). Data were analyzed and treated using Microsoft Excel and GIS software us as Golden Surfer, Global Mapper, and ArcGIS. The results show variations of water level and those areas that may threaten foundation construction. Quarter as Kumba Station, Mile 1, Bulletin Street (Fongong Quarter), and parts of Fiango show that water table is to deep water and proper for the shallow foundation but very hard for water supply through borehole. Groundwater flow direction was revealed to be towards the south and southeastern parts of Kumba. The significant of the study is to propose to the technician the direct application on the field of chosen types of foundations according to the quarter and proposed groundwater supply possibilities.展开更多
Due to the rapid propagation characteristic of the Coronavirus(COVID-19)disease,manual diagnostic methods cannot handle the large number of infected individuals to prevent the spread of infection.Despite,new automated...Due to the rapid propagation characteristic of the Coronavirus(COVID-19)disease,manual diagnostic methods cannot handle the large number of infected individuals to prevent the spread of infection.Despite,new automated diagnostic methods have been brought on board,particularly methods based on artificial intelligence using different medical data such as X-ray imaging.Thoracic imaging,for example,produces several image types that can be processed and analyzed by machine and deep learning methods.X-ray imaging materials widely exist in most hospitals and health institutes since they are affordable compared to other imaging machines.Through this paper,we propose a novel Convolutional Neural Network(CNN)model(COV2Net)that can detect COVID-19 virus by analyzing the X-ray images of suspected patients.This model is trained on a dataset containing thousands of X-ray images collected from different sources.The model was tested and evaluated on an independent dataset.In order to approve the performance of the proposed model,three CNN models namely Mobile-Net,Residential Energy Services Network(Res-Net),and Visual Geometry Group 16(VGG-16)have been implemented using transfer learning technique.This experiment consists of a multi-label classification task based on X-ray images for normal patients,patients infected by COVID-19 virus and other patients infected with pneumonia.This proposed model is empowered with Gradient-weighted Class Activation Mapping(Grad-CAM)and Grad-Cam++techniques for a visual explanation and methodology debugging goal.The finding results show that the proposed model COV2Net outperforms the state-of-the-art methods.展开更多
This paper focuses on the study of the physical, biochemical, structural, and thermal properties of plant fibres of <i>Rhecktophyllum camerunense</i> (RC), <i>Neuropeltis acuminatas</i> (NA) an...This paper focuses on the study of the physical, biochemical, structural, and thermal properties of plant fibres of <i>Rhecktophyllum camerunense</i> (RC), <i>Neuropeltis acuminatas</i> (NA) and <i>Ananas</i> <i>comosus</i> (AC) from the equatorial region of Cameroon. The traditional use of these fibres inspired researchers to investigated their properties. This study aims at improving the state of knowledge with a view to diversifying applications. The fibres are extracted by retting. Then, their apparent density was measured following the ASTM D792 standard and their water moisture absorption and moisture content were also evaluated. Their molecular structure was studied by ATR-FTIR spectroscopy. A quantitative analysis of the biochemical composition was performed according to the analytical technique for the pulp and paper industry (TAPPI). A TGA/DSC analysis was also performed. The results reveal that the AC, NA and RC fibres have densities of 1.26 ± 1.06, 0.846 ± 0.13 and 0.757 ± 0.08 g·cm<sup>-3</sup> respectively. They are also hydrophilic with a water absorption rate of 188.64 ± 11.94%, 276.16% ± 8.07% and 198.17% ± 20%. They have a moisture content of 12.21%, 10.36% and 9.37%. The studied fibres exhibit functional groups that are related to the presence of hemicellulose, pectin, lignin and cellulose. The cellulose crystallinity index was found to be 67.99%, 46.5% and 59.72% respectively. The fibres under study have the following chemical composition: an extractive content of 3.07%, 14.77% and 8.74%;a pectin content of 4.15%, 7.69% and 3.45%;a hemicellulose content of 4.90%, 15.33% and 7.42%;a cellulose content of 68.11%, 36.08% and 65.15%;a lignin content of 12.01%, 25.15% and 16.2%;and an ash content of 0.27%, 1.53% and 0.47% respectively. The thermal transitions observed on the thermograms correlate with the TAPPI chemical composition. It is observed that these fibres are thermally stable up to temperatures of 200°C, 220°C and 285°C. These results make it possible to envisage uses similar to those of sisal, hemp and flax fibres.展开更多
The use of an electrical network as close as possible to its limits can lead to its instability in the event of a high amplitude disturbance. The damping of system oscillations can be achieved by conventional means of...The use of an electrical network as close as possible to its limits can lead to its instability in the event of a high amplitude disturbance. The damping of system oscillations can be achieved by conventional means of voltage and speed regulation but also by FACTS (Flexible AC Transmission Systems) devices, which are increasingly used in power networks. In this work, optimal control coordination between a hybrid power flow controller and a three-level inverter was used to improve the transient stability of a transmission line. The UPFC is a combination of a serial compensator (SSSC) and a parallel compensator (STATCOM) both connected to a DC-LINK DC bus. The SSSC acts as a voltage source for the network and injects a voltage that can be adjusted in phase and amplitude in addition to the network voltage;the STATCOM acts as a current source. The approach used is tested in the Matlab Simulink environment on a single machine network. Optimal controller tuning gives a better transient stability improvement by reducing the transport angle oscillations from 248.17% to 9.85%.展开更多
The objective of this paper is to investigate the relative variations of the constants of the thermal properties and the degree of crystallinity of the mixtures (PP/EPR)/Calcium carbonates elaborated with the Micro Bi...The objective of this paper is to investigate the relative variations of the constants of the thermal properties and the degree of crystallinity of the mixtures (PP/EPR)/Calcium carbonates elaborated with the Micro Bivis. We have strengthened the basic copolymer PP/EPR of a low level (5%) by three calcium carbonates models socal312, socal322v, Winnofil spm. We then subjected the different mixtures obtained, two cycles of a thermal loading under differential scanning calorimetry DSC. We finally focused on the thermal properties of isotactic polypropylene (TfP, TcP, ΔHfP, ΔHcP) and we calculated the degree of crystallinity of the mixtures. Reducing the energy cost of implementing mixtures is one of the objectives of this work. We quantified the relative variations of the above properties with those of the base copolymer. It shows that at a low loading rate of calcium carbonate, there is a decrease in the enthalpies of crystallization during the second exothermic cycle, with values that can reach 5.53 J/gPP for the basic copolymer PP/EPR. During the second endothermic cycle, there is an overall increase in isotactic polypropylene melting temperature values for all the blends as well as for the basic copolymer PP/EPR. There is evidence that calcium carbonates are useful for lowering the melting energy of isotactic polypropylene, even at a low loading rate for the majority. The number of endothermic cycles accentuates this phenomenon which is linked to the presence in our composites, of a so-called confined amorphous phase.展开更多
The project consists in the implementation of a biocomposite based on tannin resin and natural rubber matrices with the bast fibres of <i>Triumfetta cordifolia </i>A.Rich.“<i>Okong</i>” from ...The project consists in the implementation of a biocomposite based on tannin resin and natural rubber matrices with the bast fibres of <i>Triumfetta cordifolia </i>A.Rich.“<i>Okong</i>” from the equatorial region of Cameroon as reinforcement. A study of this still little known fibre is necessary. This paper evaluates the physico-chemical and mechanical characteristics of the fibers. The fibers are extracted by us. A series of experiments is conducted for this purpose: morphological observation with a scanning electron microscope (SEM);density evaluation with a helium pycnometer;absorption rate evaluation according to the protocol available in the literature, Fourier Transform Infrared Spectrometry (FT-IR), chemical composition evaluation according to ASTM 1972 and ASTM 1977 standards, thermogravimetric analysis (TGA) and tensile tests on fiber bundles according to NF T25-501-3. The results show that the fiber is made up of several elementary fibers with oval cross-sections. A density of 1.477g/cm<sup>3</sup> close to that of hemp. These fibers have a water absorption rate of 342.5%, which correlates with the presence of free hydroxyl functional groups obtained from the spectrometry study (FT-IR). Chemical analysis reveals that the fiber is made up of celluloses (44.4%), hemicelluloses (30.8%), lignins (18.9%), pectins (3.3%), waxes (0.5%) and minerals (2.1%). In addition, we learn that the fibers studied dehydrate at 11.49%, showinga notable thermal stability around 235°C with a peak thermal decomposition of cellulose located at 420°C. In terms of mechanical behaviour, the results reveal that the fibers offer a Young’s modulus in traction of 12.4 ± 6.9 GPa, a tensile strength of 526 ± 128 MPa and an elongation at break of 2.25%. The information thus obtained makes it possible to place these fibers in the same fiber group as flax and jute. They could therefore be used for the same types of applications. They also inform us that these fibers can withstand the temperatures of composite shaping by thermocompression.展开更多
This work aims to develop and characterize a hybrid composite material with two particles of the same size. As reinforcing particles, the hulls of palm nuts and coconut are chosen. Hybrid composite material composites...This work aims to develop and characterize a hybrid composite material with two particles of the same size. As reinforcing particles, the hulls of palm nuts and coconut are chosen. Hybrid composite material composites in the form of specimens were produced by molding at 10%, 20% and 30% mass fractions in various sizes (0.63<span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm, 1.25</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm and 2.5</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm). The samples were physically characterized (water absorption rate, moisture content, actual, theoretical and apparent density) and mechanical in 3-point flexion. The main results are: the highest and minimum water absorption rate are respectively 3.57% and 0.67% for respectively particle sizes 1.25</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm (sample P10C30) and 0.67% in the size of 0.63</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm (sample P10C10). The moisture content varies from 0.64 to 7.14% respectively for the P20C20 (2.5 mm) and P10C30 (2.5 mm) samples. The maximum and minimum real density are 1340,518</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> and 1055.981</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">, for respectively the composites of particles sizes 1.25</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm (P20C10) and 0.63</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">mm (sample P20C20). The minimum real density is Its </span><span><span style="font-family:Verdana;">maximum theoretical density is 1194.949 Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> (for samples P20C10,</span></span><span style="font-family:Verdana;"> P10C10 and P30C10);however, the minimum is 1189.966 Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> (P10C20 and P20C20). The bulk density varies from 933.28</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> to 1176.1</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">, respectively, in sizes from 2.5</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm (P10C30) to 0.63</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">mm (for P10C30). As for the mechanical characteristics, the Modulus of Elasticity (MOE) varies from 25.664 GPa to 25.759 GPa, respectively, the samples P10C10 (1.25 mm) and P10C20 (2.5 mm). The MOE values describe a parabola whose peak is reached when the palm shell loads are 20%, that is to say P20C10, whatever the particle size distribution. In resilience, samples with small particles are more resilient with a maximum value of 22.49 J/cm</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> and a minimum value of 4.45 J/cm</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> to verify the principles of Hall-Petch’s law.</span></span>展开更多
This article describes a technique that allows a photovoltaic (PV) production unit to obtain the maximum power at all times. Here, we use the MPPT control via fuzzy logic on a DC/DC boost-type converter. In order to a...This article describes a technique that allows a photovoltaic (PV) production unit to obtain the maximum power at all times. Here, we use the MPPT control via fuzzy logic on a DC/DC boost-type converter. In order to achieve our goals, we first proceeded to model a PV panel. The resulting model offers the possibility to better account for the influence of different physical quantities such as temperature, irradiation, series resistance, shunt resistance and diode saturation current. Thus, the maximum power to be provided by the PV system is acquired by fuzzification and defuzzification of the input and output variables of the converter. Subsequently, a virtual model of an 800 Watt PV prototype is implemented in the Matlab environment. The simulation results obtained and presented, show the feasibility and efficiency of the proposed technology. Indeed, for a disturbance caused by a variation in brightness, our system guarantees the maximum stable power after 1.4</span><span style="font-family:Verdana;"> </span><span style="font-family:Verdana;">s. While for a load variation, the maximum power is continuous.展开更多
This article contributes to the development of the new class of fully biodegradable “green” composites by combining fibers (natural/bio) with biodegradable resin. The vegetable fibers (Triumfetta cordifolia and suga...This article contributes to the development of the new class of fully biodegradable “green” composites by combining fibers (natural/bio) with biodegradable resin. The vegetable fibers (Triumfetta cordifolia and sugarcane bagasse) treated with NaOH and bleached were incorporated into a natural rubber matrix. The influence of the fiber ratio on the physical properties, tensile strength and surface hardness of the hybrid composites was analyzed. The results show that the addition of fibers in the natural rubber matrix increases the water absorption capacity but gradually reduces it with increasing fiber ratio. The hybrid composites of the NRT50-50B proportions show the best tensile strengths at 20 phr and a shore A hardness of 43.7 at 30 phr. The combination of two fibers has improved the physical and mechanical properties of the hybrid composites which can be used in engineering applications.展开更多
文摘The use of plastics from petrochemical resources poses environmental impacts, and one of the alternative solutions is the use of starch. The objective of this present work has been to present the literature on starch, and to highlight the debate in the development of composite films. The approach adopted was to present the state of the art on starch and thermoplastic starch matrix composites. The work shows that starch is available worldwide and can be used in the manufacture of biodegradable plastics;the debate remains on the reinforcement of thermoplastic starch to improve its physical and mechanical properties poor;then researchers must diversify the reinforcements to see the impact on the properties of thermoplastic starch.
文摘This work is part of the resolution of problems encountered on a 225 KV MANGOMBE-OYOMABANG line. This line is characterized by important technical losses, so that the voltage injected in the busbar is always lower than 200kV. The main objective of this work is to show the new solutions that can provide a combined FACTS-STATCOM and IPC 240 dual system on this line. Then to show the limitation of STATCOM compared to RPI 240. The results obtained allowed us to observe that in symmetrical operation the STATCOM improves the voltage profile on the busbar and in asymmetrical operation we found that it continues to regulate the voltage of each phase despite the unbalance. But the system remains too unbalanced because of the sequence current flow. The IPC 240 corrects this limitation, allowing asymmetrical operation of the line in an emergency while providing continuous service to the load.
文摘This article systematically delves into a comprehensive analysis of the latest and most advanced techniques for the assessment of slope stability. It particularly focuses on strategies aimed at enhancing slope stability in road construction. In addition to this analysis, the article presents an illustrative case study centered on the Toffo-Lalo Road Project. The core objective of this paper is to scrutinize the stability of large embankments in road construction, with a specific emphasis on the development and asphalt overlay of the Toffo-Lalo road. This scrutiny is conducted through the utilization of stability calculation software, GEOSTUDIO2018, specifically its SLOPE/W module. Within this framework, a detailed model of the cutbank located at KP1+750-2+250 was meticulously developed. This model takes into account the physical-mechanical characteristics of the soil at the site, as well as the topographic layout. Its attributes include a cohesion value of 11.3 Kpa, a density of 16.57 KN/m<sup>3</sup>, and a friction angle of 27˚. The modeling results, employing the Morgenstern-Price method—an approach renowned for its adherence to equilibrium conditions and provision of precise results—conclude that the safety coefficient (Fs = 1.429) prior to any reinforcement signifies a critical state of slope stability. To address this, the article explores the implementation of reinforcement techniques, particularly focusing on rigid inclusions like nailing and piles. The modeling exercises reveal a noteworthy enhancement in the safety coefficient (Fs) post-reinforcement. Furthermore, the article undertakes a parametric study to optimize the reinforcement strategies. This analysis highlights that anchoring at 0˚ downward relative to the horizontal plane and employing a pile angle of 90˚ represent the most favorable approaches. These measures yield safety coefficients of 3.60 and 2.34, respectively, indicating substantially improved slope stability.
文摘Lima bean is a tropical and subtropical legume from the genus Phaseolus which is cultivated for its importance in food and in medicine, but which remains a Neglected and Underutilized Crop in Benin. Understanding the genetic diversity of a species’ genetic resources is useful for the establishment of appropriate conservation strategies and breeding programs and for sustainable use. We use 6 out of ten SSR markers to analyze the diversity and population structure of 28 Lima bean landraces collected in Benin. A total of 28 alleles with an average of 4.16 alleles per SSR were amplified. The Polymorphic Information Content value ranged from 0.079 to 0.680 with an average of 0.408. The analysis of population structure revealed three subpopulations. PCoA revealed three well-separated clusters among the analyzed accessions in accordance with the population structure results and the clustering based on the Neighbor-Joining tree. AMOVA showed highly significant (p = 0.001) diversity among and within populations. Hence, 32% of the genetic variation was distributed among the population and 68% was distributed within populations. A high PhiP value (0.321) was found between the three sub-subpopulations indicating a high genetic differentiation between these sub-subpopulations. By exhibiting the highest average number of alleles, Shannon-Weaver information and Shannon-Weaver diversity indices, and the highest mean number of private alleles, subpopulation 1 is the main gene pool of the analyzed collection. The present study is an important starting point for the establishment of appropriate conservation strategies and breeding programs for Lima bean genetic resources.
文摘The aim of this work was to propose a possibility of using plastic aggregates from waste to reduce the shrinkage and expansion observed in concrete. The process of obtaining plastic aggregates was presented. Natural aggregates were partially substituted by plastic aggregates in the percentages: 0%, 5%, 10%, 20% and 30%. Drying shrinkage, water absorption and expansion tests were carried out on three families of concrete: control concrete (BT), concrete with addition of BAgP-PEHD high-density polyethylene plastic aggregate and with polyvinyl chloride BAgP-PVC. Given the slow appearance of the internal sulfate attack (ISA), an experimental technique was proposed to accelerate the appearance of this pathology. This technique involves heat treatment which stimulates the heating of the concrete at a young age, followed by a cycle of drying and cooling and ends with total immersion in water. The method of measuring expansions through sample image correlation was also proposed. The results showed an increased skrinkage of BAgP-HDPE compared to BT. On the other hand, a significant decrease in shrinkage was observed in BAgP-PVC samples. Water absorption increased in BAgP-HDPE and BAgP-PVC compared to BT. Greater expansion was observed at the cement paste-plastic aggregate interface than at the cement paste-natural aggregate interface. Given these properties, BAgP-PVC can be recommended for paving surfaces exposed to the hard weather conditions.
文摘Structures erected on swelling clay soils are subjected to several stresses which are at the origin of the premature deterioration of the infrastructures. The soils being supports for the works, the improvement of their weak characteristics with cotton fibers will not only increase the bearing capacities of these soils and the resolution of the environmental problem, by eliminating the CO<sub>2</sub> produced by the burning of the stems after harvest. The objective of this study is to contribute to the improvement of the characteristics by cotton stalk powder of the swelling clay soils used as the foundation of the infrastructures in order to guarantee their durability. Identification and mechanical parameterization tests were carried out on raw soil samples taken at 1.5 meters deep and on samples improved with cotton stalk powder at different levels (3%, 6% and 10%). The results from the physical tests reveal that the soil studied is very plastic silt. As for the mechanical tests, it appears that by adding 3% cotton stalk powder to dry density which goes from 1.435 t/m<sup>3</sup> compared to the control sample with a dry density of 1.50 t/m<sup>3</sup>;which reflects an improvement in the compaction characteristics of the soil studied. The dry densities are 1.445 t/m<sup>3</sup> and 1.29 t/m<sup>3</sup> for the samples improved with 6% and 10% cotton stalk powder.
文摘This comprehensive review paper explores various aspects of geotechnical engineering, with a focus on the management of unstable terrains, numerical methods for solving complex soil and consolidation problems, rheological analysis of suspensions and muddy soils, and stability analysis of slopes. It begins by examining the unique physicochemical properties of cohesive sediments, including cohesion and specific surface area. The temporal evolution of deposit concentration and average bed concentration in unstable terrains is discussed, along with settling behavior of isolated particles and hindered settling using empirical equations. Key sedimentation theories, such as Kynch’s theory, and geotechnical consolidation theories, including Terzaghi’s consolidation equation and Gibson’s theory, are presented. The investigation interrelates these theories and principles to offer a holistic view of managing unstable terrains. It also addresses the challenges associated with experimental determination of constitutive relationships and presents alternative simplification methods proposed by researchers. Additionally, it delves into numerical methods for solving nonlinear partial differential equations governing soil behavior, emphasizing the need for numerical frameworks and discussing various techniques and associated challenges. The rheological analysis section covers material flow behavior, rheological behavior models, and the rheological properties of water and cohesive sediment mixtures. Fundamental geotechnical calculations, constitutive laws, and failure criteria are explained, highlighting their relevance in geotechnical engineering applications. This paper provides a multidimensional perspective on geotechnical engineering, offering valuable insights into soil properties, consolidation processes, numerical methods, rheological analysis, and slope stability assessment for professionals in the field.
文摘This document presents a study of the behaviour of a pavement structure on compressible soil and the evaluation of its durability. The objective of this study is to highlight the impact of taking into account the non-linear elastic behaviour of soils and granular materials in the design process. To this end, a numerical modelling of the pavement of the beau-rivage-Djassin crossroads section in Porto-Novo was carried out, based on a compressible soil whose behaviour will be considered elastoplastic. The subgrade soil on the section is made up of several sub-layers. The layer of soft, highly plastic clay was modelled according to a modified Cam Clay behaviour, a model of swelling clay soils. The fine sand layer and the granular layers of the structure are modelled according to Mohr-Coulomb behaviour. The loading is considered to be uniformly distributed according to the assumptions of the Burmister model in the French standard. A first verification with ALIZE allowed to validate the structure on the basis of the rutting deformation at the head of the platform ε<sub>z</sub> = 359.6*10<sup>-6</sup> which remains lower than the admissible deformation ε<sub>z</sub><sub>,adm</sub> = 360*10<sup>-6</sup>. The numerical calculation was carried out using the finite element method, the code of which is implemented under the PLAXIS v21 software. A comparative study with the results of the ALIZE design revealed that the numerically calculated strains ε<sub>z</sub> = 585*10<sup>-6</sup> are higher than those of ALIZE. These numerical strains, which are higher than the elastic strains, do not meet the validation criteria that the strains under loading must remain below the allowable strains. An evaluation of the pavement durability was carried out and it was found that the pavement would only last under traffic for 3 years before the first fatigue deformations appeared.
文摘This work focuses on the valorization of local materials.The rock that is granite,a material used in construction thanks to its mechanical resistance,is the subject of our study.The granite of the commune of Savè,made it possible to appreciate the thermal behavior of this rock studied with a view to its use as a building material.To this end,a thermal diffusivity measurement test was carried out on this material.Thus,we made samples which were then connected to a data acquisition box via thermocouples.A Python script is used to ensure the collection of temperature values over time.From this thermal diffusivity test carried out on the granite taken from the Savèbreasts,we obtained an average diffusivity a=5.84×10^(-6)m^(2)/s.As a result,the thermal effusivity and the heat capacity of the material were determined having respectively the value 1,351.09 J/(K·m^(2)·s^(1/2))and 547,945.21 J/(m^(3)·K).These different results highlight a thermal characterization of Savègranites as a relevant material in the design and construction of an energy-efficient eco-housing.
文摘The importance of slope stability in civil engineering cannot be underestimated, as failure of these structures can result in significant damage to downstream infrastructure and property. In this study, we used the Bishop slice method, combining both an analytical approach and a numerical approach using the SLOPE/W module of the Geostudio 2018 R2 software. The results obtained from these two methods showed that increasing soil cohesion helps to improve slope stability. The safety coefficients obtained by the analytical method vary between 0.621 and 1.422, while those obtained by the numerical method vary between 0.622 and 1.447, for cohesion values ranging from 4 kPa to 20 kPa. The results obtained by these two methods show a linear relationship between the safety coefficients and soil cohesion. The equation of the analytical method is y = 0.0496x + 0.4407, while that of the numerical method is y = 0.0512x + 0.4357. The results of the analytical approach indicate that a safety coefficient of 1.5 is reached when the cohesion reaches a value of 22 kPa, while the numerical approach shows a safety coefficient of 1.5 reached at a cohesion of 21 kPa. The difference between these two cohesion values can be explained by the number of slices used, which is smaller in the analytical method. However, the equation derived from the analytical method can be used as a general guide to assess the evolution of the safety coefficient of an overloaded slope in long-term behaviour with an increase in cohesion. However, it is important to stress the importance of verification using specialised software based on the finite element method.
文摘This work focuses on the design of a new type of eco-material based on Typha“Domingensis”and clay from the south of the Republic of Benin through various dosages.Three particle size classes of typha shavings were selected to be mixed with two types of clayin order to make parallelepiped shaped samples ready for experimentation.The massive use of these briquettes thus obtained,in the construction of habitats,would not only contribute to reducing the energy consumption inside the dwellings but also would limit the invasion of the waterways of Benin,which would facilitate navigation,fishing and river sanitation activities.In addition,this biosourced,low-polluting material would contribute to improving the energy transition by integrating it into rehabilitation of buildings.
文摘The rapid economic growth of the town present the matter of water issue as a problem to human life human life, construction life, agriculture, etc. This study is to predict techniques of foundation construction through the displaying of the water table at the flow direction in the town of Kumba and GIS. It is characterized by a significant research question which is the level of fall and rise in groundwater levels within the town of Kumba and this influence on choice of types of foundation in construction. This study is directed to decision makers, and technicians of the construction field to develop policies facilitating the supervision when building construction foundation by informing about water level depth and its flow direction in the town. To achieve this, depths of static water levels were measured in over 200 randomly selected hand-dug wells in Kumba, after their geolocation and data were collected during the dry season (November and March 2017) and during the rainy season (between April and October 2017). Data were analyzed and treated using Microsoft Excel and GIS software us as Golden Surfer, Global Mapper, and ArcGIS. The results show variations of water level and those areas that may threaten foundation construction. Quarter as Kumba Station, Mile 1, Bulletin Street (Fongong Quarter), and parts of Fiango show that water table is to deep water and proper for the shallow foundation but very hard for water supply through borehole. Groundwater flow direction was revealed to be towards the south and southeastern parts of Kumba. The significant of the study is to propose to the technician the direct application on the field of chosen types of foundations according to the quarter and proposed groundwater supply possibilities.
基金This research is funded by the Deanship of Scientific Research at King Khalid University through Large Groups.(Project under grant number(RGP.2/111/43)).
文摘Due to the rapid propagation characteristic of the Coronavirus(COVID-19)disease,manual diagnostic methods cannot handle the large number of infected individuals to prevent the spread of infection.Despite,new automated diagnostic methods have been brought on board,particularly methods based on artificial intelligence using different medical data such as X-ray imaging.Thoracic imaging,for example,produces several image types that can be processed and analyzed by machine and deep learning methods.X-ray imaging materials widely exist in most hospitals and health institutes since they are affordable compared to other imaging machines.Through this paper,we propose a novel Convolutional Neural Network(CNN)model(COV2Net)that can detect COVID-19 virus by analyzing the X-ray images of suspected patients.This model is trained on a dataset containing thousands of X-ray images collected from different sources.The model was tested and evaluated on an independent dataset.In order to approve the performance of the proposed model,three CNN models namely Mobile-Net,Residential Energy Services Network(Res-Net),and Visual Geometry Group 16(VGG-16)have been implemented using transfer learning technique.This experiment consists of a multi-label classification task based on X-ray images for normal patients,patients infected by COVID-19 virus and other patients infected with pneumonia.This proposed model is empowered with Gradient-weighted Class Activation Mapping(Grad-CAM)and Grad-Cam++techniques for a visual explanation and methodology debugging goal.The finding results show that the proposed model COV2Net outperforms the state-of-the-art methods.
文摘This paper focuses on the study of the physical, biochemical, structural, and thermal properties of plant fibres of <i>Rhecktophyllum camerunense</i> (RC), <i>Neuropeltis acuminatas</i> (NA) and <i>Ananas</i> <i>comosus</i> (AC) from the equatorial region of Cameroon. The traditional use of these fibres inspired researchers to investigated their properties. This study aims at improving the state of knowledge with a view to diversifying applications. The fibres are extracted by retting. Then, their apparent density was measured following the ASTM D792 standard and their water moisture absorption and moisture content were also evaluated. Their molecular structure was studied by ATR-FTIR spectroscopy. A quantitative analysis of the biochemical composition was performed according to the analytical technique for the pulp and paper industry (TAPPI). A TGA/DSC analysis was also performed. The results reveal that the AC, NA and RC fibres have densities of 1.26 ± 1.06, 0.846 ± 0.13 and 0.757 ± 0.08 g·cm<sup>-3</sup> respectively. They are also hydrophilic with a water absorption rate of 188.64 ± 11.94%, 276.16% ± 8.07% and 198.17% ± 20%. They have a moisture content of 12.21%, 10.36% and 9.37%. The studied fibres exhibit functional groups that are related to the presence of hemicellulose, pectin, lignin and cellulose. The cellulose crystallinity index was found to be 67.99%, 46.5% and 59.72% respectively. The fibres under study have the following chemical composition: an extractive content of 3.07%, 14.77% and 8.74%;a pectin content of 4.15%, 7.69% and 3.45%;a hemicellulose content of 4.90%, 15.33% and 7.42%;a cellulose content of 68.11%, 36.08% and 65.15%;a lignin content of 12.01%, 25.15% and 16.2%;and an ash content of 0.27%, 1.53% and 0.47% respectively. The thermal transitions observed on the thermograms correlate with the TAPPI chemical composition. It is observed that these fibres are thermally stable up to temperatures of 200°C, 220°C and 285°C. These results make it possible to envisage uses similar to those of sisal, hemp and flax fibres.
文摘The use of an electrical network as close as possible to its limits can lead to its instability in the event of a high amplitude disturbance. The damping of system oscillations can be achieved by conventional means of voltage and speed regulation but also by FACTS (Flexible AC Transmission Systems) devices, which are increasingly used in power networks. In this work, optimal control coordination between a hybrid power flow controller and a three-level inverter was used to improve the transient stability of a transmission line. The UPFC is a combination of a serial compensator (SSSC) and a parallel compensator (STATCOM) both connected to a DC-LINK DC bus. The SSSC acts as a voltage source for the network and injects a voltage that can be adjusted in phase and amplitude in addition to the network voltage;the STATCOM acts as a current source. The approach used is tested in the Matlab Simulink environment on a single machine network. Optimal controller tuning gives a better transient stability improvement by reducing the transport angle oscillations from 248.17% to 9.85%.
文摘The objective of this paper is to investigate the relative variations of the constants of the thermal properties and the degree of crystallinity of the mixtures (PP/EPR)/Calcium carbonates elaborated with the Micro Bivis. We have strengthened the basic copolymer PP/EPR of a low level (5%) by three calcium carbonates models socal312, socal322v, Winnofil spm. We then subjected the different mixtures obtained, two cycles of a thermal loading under differential scanning calorimetry DSC. We finally focused on the thermal properties of isotactic polypropylene (TfP, TcP, ΔHfP, ΔHcP) and we calculated the degree of crystallinity of the mixtures. Reducing the energy cost of implementing mixtures is one of the objectives of this work. We quantified the relative variations of the above properties with those of the base copolymer. It shows that at a low loading rate of calcium carbonate, there is a decrease in the enthalpies of crystallization during the second exothermic cycle, with values that can reach 5.53 J/gPP for the basic copolymer PP/EPR. During the second endothermic cycle, there is an overall increase in isotactic polypropylene melting temperature values for all the blends as well as for the basic copolymer PP/EPR. There is evidence that calcium carbonates are useful for lowering the melting energy of isotactic polypropylene, even at a low loading rate for the majority. The number of endothermic cycles accentuates this phenomenon which is linked to the presence in our composites, of a so-called confined amorphous phase.
文摘The project consists in the implementation of a biocomposite based on tannin resin and natural rubber matrices with the bast fibres of <i>Triumfetta cordifolia </i>A.Rich.“<i>Okong</i>” from the equatorial region of Cameroon as reinforcement. A study of this still little known fibre is necessary. This paper evaluates the physico-chemical and mechanical characteristics of the fibers. The fibers are extracted by us. A series of experiments is conducted for this purpose: morphological observation with a scanning electron microscope (SEM);density evaluation with a helium pycnometer;absorption rate evaluation according to the protocol available in the literature, Fourier Transform Infrared Spectrometry (FT-IR), chemical composition evaluation according to ASTM 1972 and ASTM 1977 standards, thermogravimetric analysis (TGA) and tensile tests on fiber bundles according to NF T25-501-3. The results show that the fiber is made up of several elementary fibers with oval cross-sections. A density of 1.477g/cm<sup>3</sup> close to that of hemp. These fibers have a water absorption rate of 342.5%, which correlates with the presence of free hydroxyl functional groups obtained from the spectrometry study (FT-IR). Chemical analysis reveals that the fiber is made up of celluloses (44.4%), hemicelluloses (30.8%), lignins (18.9%), pectins (3.3%), waxes (0.5%) and minerals (2.1%). In addition, we learn that the fibers studied dehydrate at 11.49%, showinga notable thermal stability around 235°C with a peak thermal decomposition of cellulose located at 420°C. In terms of mechanical behaviour, the results reveal that the fibers offer a Young’s modulus in traction of 12.4 ± 6.9 GPa, a tensile strength of 526 ± 128 MPa and an elongation at break of 2.25%. The information thus obtained makes it possible to place these fibers in the same fiber group as flax and jute. They could therefore be used for the same types of applications. They also inform us that these fibers can withstand the temperatures of composite shaping by thermocompression.
文摘This work aims to develop and characterize a hybrid composite material with two particles of the same size. As reinforcing particles, the hulls of palm nuts and coconut are chosen. Hybrid composite material composites in the form of specimens were produced by molding at 10%, 20% and 30% mass fractions in various sizes (0.63<span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm, 1.25</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm and 2.5</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm). The samples were physically characterized (water absorption rate, moisture content, actual, theoretical and apparent density) and mechanical in 3-point flexion. The main results are: the highest and minimum water absorption rate are respectively 3.57% and 0.67% for respectively particle sizes 1.25</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm (sample P10C30) and 0.67% in the size of 0.63</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm (sample P10C10). The moisture content varies from 0.64 to 7.14% respectively for the P20C20 (2.5 mm) and P10C30 (2.5 mm) samples. The maximum and minimum real density are 1340,518</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> and 1055.981</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">, for respectively the composites of particles sizes 1.25</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm (P20C10) and 0.63</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">mm (sample P20C20). The minimum real density is Its </span><span><span style="font-family:Verdana;">maximum theoretical density is 1194.949 Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> (for samples P20C10,</span></span><span style="font-family:Verdana;"> P10C10 and P30C10);however, the minimum is 1189.966 Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> (P10C20 and P20C20). The bulk density varies from 933.28</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> to 1176.1</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Kg/m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">, respectively, in sizes from 2.5</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mm (P10C30) to 0.63</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">mm (for P10C30). As for the mechanical characteristics, the Modulus of Elasticity (MOE) varies from 25.664 GPa to 25.759 GPa, respectively, the samples P10C10 (1.25 mm) and P10C20 (2.5 mm). The MOE values describe a parabola whose peak is reached when the palm shell loads are 20%, that is to say P20C10, whatever the particle size distribution. In resilience, samples with small particles are more resilient with a maximum value of 22.49 J/cm</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> and a minimum value of 4.45 J/cm</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> to verify the principles of Hall-Petch’s law.</span></span>
文摘This article describes a technique that allows a photovoltaic (PV) production unit to obtain the maximum power at all times. Here, we use the MPPT control via fuzzy logic on a DC/DC boost-type converter. In order to achieve our goals, we first proceeded to model a PV panel. The resulting model offers the possibility to better account for the influence of different physical quantities such as temperature, irradiation, series resistance, shunt resistance and diode saturation current. Thus, the maximum power to be provided by the PV system is acquired by fuzzification and defuzzification of the input and output variables of the converter. Subsequently, a virtual model of an 800 Watt PV prototype is implemented in the Matlab environment. The simulation results obtained and presented, show the feasibility and efficiency of the proposed technology. Indeed, for a disturbance caused by a variation in brightness, our system guarantees the maximum stable power after 1.4</span><span style="font-family:Verdana;"> </span><span style="font-family:Verdana;">s. While for a load variation, the maximum power is continuous.
文摘This article contributes to the development of the new class of fully biodegradable “green” composites by combining fibers (natural/bio) with biodegradable resin. The vegetable fibers (Triumfetta cordifolia and sugarcane bagasse) treated with NaOH and bleached were incorporated into a natural rubber matrix. The influence of the fiber ratio on the physical properties, tensile strength and surface hardness of the hybrid composites was analyzed. The results show that the addition of fibers in the natural rubber matrix increases the water absorption capacity but gradually reduces it with increasing fiber ratio. The hybrid composites of the NRT50-50B proportions show the best tensile strengths at 20 phr and a shore A hardness of 43.7 at 30 phr. The combination of two fibers has improved the physical and mechanical properties of the hybrid composites which can be used in engineering applications.