Many attempts have been made to estimate calorific value of bagasse using mathematical equations, which were created based on data from proximate, ultimate, physical and chemical analysis. Questions have been raised o...Many attempts have been made to estimate calorific value of bagasse using mathematical equations, which were created based on data from proximate, ultimate, physical and chemical analysis. Questions have been raised on the applicability of these equations in different parts of the globe. This study was initiated to tackle these problems and also check the most suited mathematical models for the Law Heating Value of Cameroonian bagasse. Data and bagasse samples were collected at the Cameroonian sugarcane factory. The effects of cane variety, age of harvesting, source, moisture content, and sucrose on the LHV of Cameroon bagasse have been tested. It was shown that humidity does not change within a variety, but changes from the dry season to the rainy season;the sugar in the rainy season is significantly different from that collected in the dry season. Samples of the same variety have identical LHV. LHV in the dry season is significantly different from LHV in the rainy season. According to the fact that this study was done for cane with different ages of harvesting, the maturity of Cameroonian sugarcane does not affect LHV of bagasse. Tree selected models are much superior tool for the prediction of the LHV for bagasse in Cameroon compared to others. The standard deviation of these validated models is around 200 kJ/kg compared to the experimental. Thus, the models determined in foreign countries, are not necessarily applicable in predicting the LHV of bagasse in other countries with the same accuracy as that in their native country. There was linear relationship between humidity, ash and sugar content in the bagasse. It is possible to build models based on data from physical composition of bagasse using regression analysis.展开更多
The objective of this work is to improve the physical and mechanical properties of stabilized earth blocks (BTC) used in construction in the Ndé department of Cameroon. To achieve this, two stabilizers, cement an...The objective of this work is to improve the physical and mechanical properties of stabilized earth blocks (BTC) used in construction in the Ndé department of Cameroon. To achieve this, two stabilizers, cement and sawdust, were used at varying percentages of 0%, 4%, 6%, and 8%. Physical characterization tests, including natural water content, specific weight, jar test, Protor, and Atterberg limits, were conducted. Additionally, mechanical tests, such as compression and three-point bending, were performed. The results show that as the amount of stabilizer increases, the density of BTC decreases. The samples with 8% sawdust have the highest density, while those without stabilizers have the lowest. Porosity decreases as sawdust and cement content increases, with smaller values observed in samples with 8% sawdust or cement. Our tests indicate that blocks stabilized with cement have slightly higher compressive strength than those stabilized with sawdust. However, the water absorption rate increases with higher sawdust content.展开更多
The objective of this paper is to evaluate the reliability of a system in its different states (absence of failures, partial failure and total failure) and to propose actions to improve this reliability by an approach...The objective of this paper is to evaluate the reliability of a system in its different states (absence of failures, partial failure and total failure) and to propose actions to improve this reliability by an approach based on Monte Carlo simulation. It consists of a probabilistic evaluation based on Markov Chains. In order to achieve this goal, the functionalities of Markov Chains and Monte Carlo simulation steps are deployed. The application is made on a production system. .展开更多
Energy is a crucial material for the development of our economy.Access to sufficient energy remains a major concern for developing countries,particularly those in sub-Saharan Africa.The major challenge lies in access ...Energy is a crucial material for the development of our economy.Access to sufficient energy remains a major concern for developing countries,particularly those in sub-Saharan Africa.The major challenge lies in access to clean,environmentally friendly,quality and low-cost energy in different households in our municipalities.To cope with this vast energy gap,many households are dependent on fossil fuels.In Cameroon,the consumption of wood for the supply of energy is increasing by 4%per year.Overall,approximately 80%of households in Cameroon depend on woody biomass as the sole main source of energy supply in Cameroon and demand is growing over time.In view of the climatic variations that our countries,particularly Cameroon,undergo through deforestation,the use of wood as a source of energy is expensive and harmful to the environment,hence the urgency of replacing wood with renewable energy.Biogas is one of the most versatile sources of renewable energy.On an industrial scale,it is important to automate the process control.The main objective of the present work is to model the anaerobic digestion of coffee and cocoa hulls using the particle swarm optimisation method.Pretreatment using the organosolv process was done.This resulted in 48%lignin removal and 22%cellulose increase.For the pretreated biomass,the maximum production rate was 21 NmLCH4 per day with a biomethane yield of 90 NmLCH4/gVS.This represents an enhancement of 117%in biomethane yield.A positive flammability test was recorded after the 10th day of retention time.Moreover,the data collected during anaerobic digestion allowed implementation of a two-phase mathematical model.The thirteen parameters of the model were estimated with particle swarm optimisation method in Matlab.The model was able to simulate the biomethane production kinetics and variation of volatile fatty acid concentration.展开更多
Many physical processes have nonlinear behavior which can be well represented by a polynomial NARX or NARMAX model. The identification of such models has been widely explored in literature. The majority of these appro...Many physical processes have nonlinear behavior which can be well represented by a polynomial NARX or NARMAX model. The identification of such models has been widely explored in literature. The majority of these approaches are for the open-loop identification. However, for reasons such as safety and production restrictions, open-loop identification cannot always be done. In such cases, closed-loop identification is necessary. This paper presents a two-step approach to closed-loop identification of the polynomial NARX/NARMAX systems with variable structure control （VSC）. First, a genetic algorithm （GA） is used to maximize the similarity of VSC signal to white noise by tuning the switching function parameters. Second, the system is simulated again and its parameters are estimated by an algorithm of the least square （LS） family. Finally, simulation examples are given to show the validity of the proposed approach.展开更多
This paper presents a fluoride health risk characterization approach to identify the hyper-sensitive population of adverse effect like tooth decay, dental fluorosis and skeletal fluorosis. In this context, a sampling ...This paper presents a fluoride health risk characterization approach to identify the hyper-sensitive population of adverse effect like tooth decay, dental fluorosis and skeletal fluorosis. In this context, a sampling campaign has been done over 100 Tunisian water consumption points (tap). Laboratory analysis results show that the quality of drinking water is affected by high fluoride concentration level exceeding 2 mg·L-1. Over these samples, 7% of them present non-compliant with the Tunisian national standard (NT09.14) and the international guidelines (World Health Organization recommendations, WHO). The overtake cases are located essentially in southern Tunisian areas, i.e. Medenine, Gabes, Gafsa and Tataouine. One can highlight that groundwater, in these southern Tunisian areas, are naturally rich of fluoride. This is because of the aquifers geological and fossil nature. However, commonly northern and central Tunisian areas are characterized by low fluoride concentration level below 0.1 mg·L-1. These undertaken cases don’t meet the water quality requirement defined by WHO.展开更多
The objective of this paper is to develop an efficient P wave detection method in electrocardiogram (ECG) using the local entropy criterion (EC) and wavelet transform (WT) modulus maxima. The detection of P wave relat...The objective of this paper is to develop an efficient P wave detection method in electrocardiogram (ECG) using the local entropy criterion (EC) and wavelet transform (WT) modulus maxima. The detection of P wave relates to the diagnosis of many heart diseases and it is also a difficult point during the ECG signal detection. Determining the position of a P-wave is complicated due to the low amplitude, the ambiguous and changing form of the complex. In a first step, QRS complexes are detected using the pan-Tompkins method. Then, we look for the best position of the analysis window and the value of the most appropriate width to the P wave. Finally, the determination of P wave peaks, as well as their onsets and offsets. The method has been validated using ECG-recordings with a wide variety of P-wave morphologies from MIT-BIH Arrhythmia and QT database. The P-wave method obtains a sensitivity of 99.87% and a positive predictivity of 98.04% over the MIT-BIH Arrhythmia, while for the QT, sensitivity and predictivity over 99.8% are attained.展开更多
The sugarcane bagasse fuel is an energetic deposit opportunity for thermal and electricity generation in sugar society.Combustion behaviors,essential for effective operation of these devices are a necessity.A 3D numer...The sugarcane bagasse fuel is an energetic deposit opportunity for thermal and electricity generation in sugar society.Combustion behaviors,essential for effective operation of these devices are a necessity.A 3D numerical model has been developed in the commercial software Ansys Fluent.According to the fuel density and particle variable,this model took into account both suspension and grate model combustion.The realizable k-ε turbulent model with the P-1 model shows its advantage of describing such king problems and has been applied on the numerical model.The contour of the temperature,spices and the particle trajectory provided a clear understanding of bagasse fuel combustion in the furnace as well,bagasse particle goes through from initial heating to char combustion and its conversion to ash.The results obtained were in accordance with those of the literature.These results could be used to analyze this inexpensive combustion process for looking for the effect of design parameter change on the furnace performance.展开更多
An endoreversible model is used to simulate the dynamic behavior of a solar driven absorption refrigerator, the cycle under different operating and design conditions. A global time minimization procedure is performed ...An endoreversible model is used to simulate the dynamic behavior of a solar driven absorption refrigerator, the cycle under different operating and design conditions. A global time minimization procedure is performed to reach maximum performances. To evaluate the influence of the cold temperature on the system’s performances, results are carried out for three values of this temperature. They are presented in normalized charts for general applications. The minimum time set point temperature, entropy and maximum refrigeration load are sharp and therefore, are important to be considered for system design.展开更多
Aluminium oxide coatings were formed on aluminium substrates in oxalic acid-sulphuric acid bath. Abrasion tests of the obtained anodic layers were carried out on a pin-on-disc machine in accordance with the ISO/DP 825...Aluminium oxide coatings were formed on aluminium substrates in oxalic acid-sulphuric acid bath. Abrasion tests of the obtained anodic layers were carried out on a pin-on-disc machine in accordance with the ISO/DP 825 specifications. The rickets microhardness, D （HV0.2）, and the abrasion weight loss, Wa （mg） were measured. Influence of oxalic acid concentration （Cox）, bath temperature （T） and anodic current density （J） on D and Wa has been examined, and the sulphuric acid concentration （Csul） was maintained at 100 g.L-1. It was found that high microhardness and abrasive wear resistance of oxide layers were produced under low temperatures and high current densities with the addition of oxalic acid. The morphology and the composition of the anodic oxide layer were examined by scanning electron microscopy （SEM）, atomic force microscopy （AFM）, optical microscopy and glow-discharge optical emission spectroscopy （GDOES）. It was found that the chemistry of the anodizing electrolyte, temperature, and current density are the controlling factors of the mechanical properties of the anodic oxide layer.展开更多
This article outlines the theoretical and experimental performance studies of a cylindro-parabolic solar collector. The theoretical study consists on the establishment, through mass and energy balances, of a mathemati...This article outlines the theoretical and experimental performance studies of a cylindro-parabolic solar collector. The theoretical study consists on the establishment, through mass and energy balances, of a mathematical model to control the exiting temperature of the heating fluid as well as the temperatures of the absorber and the glass. The experimental level investigates the influence of the solar absorber tube diameter on the performances of the driving device. Several experiments were made in order to know the possibility to reach temperatures being able to ensure for example the ammonia vaporization in the generator of a solar absorption refrigeration system. These experiments were carried out under various operating and climatic conditions. The results are presented and discussed.展开更多
In this paper, we present a new robust hybrid algorithm combining successively chaotic encryption and blind watermarking of images based on the quaternionic wavelet transform (QWT) to ensure the secure transfer of dig...In this paper, we present a new robust hybrid algorithm combining successively chaotic encryption and blind watermarking of images based on the quaternionic wavelet transform (QWT) to ensure the secure transfer of digital data. The calculations of the different evaluation parameters have been performed in order to determine the robustness of our algorithm to certain attacks. The application of this hybrid algorithm on CFA (Color Filter Array) images, allowed us to guarantee the integrity of the digital data and to propose an autonomous transmission system. The results obtained after simulation of this successive hybrid algorithm of chaotic encryption and then blind watermarking are appreciated through the values of the evaluation parameters which are the peak signal-to-noise ratio (PSNR) and the correlation coefficient (CC), and by the visual observation of the extracted watermarks before and after attacks. The values of these parameters show that this successive hybrid algorithm is robust against some conventional attacks.展开更多
The effect of dietary supplementation with mango (Mangifera indica L.) powder obtained by microwave dehydration was studied in normal and hypercholesterolemic mice. The phenolic profiles in methanolic extracts and ant...The effect of dietary supplementation with mango (Mangifera indica L.) powder obtained by microwave dehydration was studied in normal and hypercholesterolemic mice. The phenolic profiles in methanolic extracts and antioxidant activities were determined using high-performance liquid chromatography and DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2'-azino-bis-3-ethyl-benzothiazoline-6-sulphonic acid) assays, respectively. The total phenolic content of microwave-dehydrated mango powder was 1451.7 ± 26.7 μggallic acid equivalents/g dry weight. The main phenolic compounds identified were gallic acid, epicatechin, ferulic acid, and catechin. The anti-oxidant activity was 14.6% higher in microwave-dehydrated mango powder than in conventional mango powder. Mice were fed a hypercholesterolemic diet (1 g cholesterol/100g over 7 days). The hypercholesterolemic mice whose diets were supplemented with microwave-dehydrated mango powder showed a significant decrease (P ≤ 0.05) in total serum cholesterol compared to the hypercholesterolemic mice and the mice fed with conventional dehydrated mango powder. We observed a significant increase (P ≤ 0.05) in HDL-c levels in the microwave-dehydrated mango powder group mice (12.4 ± 1.3 mmol/L) compared to the hypercholesterolemic group (8.6 ± 1.4 mmol/L) and the conventional-dehydrated mango powder group (10.9 ± 1.3 mmol/L). The mice provided with microwave-dehydrated mango powder had significantly lower (P ≤ 0.05) levels of serum LDL-c (36.0%) and total cholesterol (43.3%) compared to the mice in hypercholesterolemic group. Notably, the atherogenic index was 72% lower in the microwave-dehydrated mango powder group compared to the hypercholesterolemic group. These results suggest that the biocompounds, such as polyphenols and dietary fiber, found in mango pulp might improve the lipid profile in mice fed a hypercholesterolemic diet.展开更多
The present study was carried out to evaluate the effect of different rates of dried cassava leafs in diet as replacement of protein sources on the weight gain and carcass yield of guinea-pigs, as well as on the physi...The present study was carried out to evaluate the effect of different rates of dried cassava leafs in diet as replacement of protein sources on the weight gain and carcass yield of guinea-pigs, as well as on the physico-chemical and technological properties of guinea-pigs’ meat. A total of forty-eight (48) eight-week-old guinea-pigs were divided in a completely randomized experimental design, in four groups and fed with the experimental foods. These experimental foods were formulated as follows: cassava-leaf (Manihot esculenta) powder was incorporated at concentrations of 0%, 8%, 10% and 12% respectively in replacement of protein sources for R0, R1, R2 and R3. Each treatment consisted of a group of 12 guinea pigs per paddock (6 males and 6 females). The initial weight (IW), final weight (FW), daily weight gain (DWG) and total gain (TG) were evaluated. At the 22nd week, animals of each group were sacrificed by bleeding, then skinned and eviscerated. Carcasses were cut, and some parts (loin, thigh and shoulder) were collected, deboned and analysed. The highest FW and carcass yield (CY) were obtained with the use of 10% cassava leafs (R2): 556 g (FW), 42.65% (CY) for males and 529.17 g (FW), 37.39% (CY) for females. The incorporation of 8% (R1) and 12% (R3) cassava leafs led to a significant increase (P < 0.05) in protein levels in the loins (22.89%) and shoulders (22.43%) of females and the thighs (21.68%) and shoulders (21.09%) of males. However, protein levels of male fed with R3 in the various parts studied were higher than females fed with the same diet. The study of the technological parameters of guinea-pig’s meat showed that the incorporation of 8% and 12% cassava leafs in the diet resulted in a significant decrease in the water holding capacity and technological yield in the different parts studied. These results show that, the incorporation of cassava leafs in guinea-pigs’ diet made it possible to obtain good growth (R2) and meat of good technological quality.展开更多
Several applications of machine learning and artificial intelligence,have acquired importance and come to the fore as a result of recent advances and improvements in these approaches.Autonomous cars are one such appli...Several applications of machine learning and artificial intelligence,have acquired importance and come to the fore as a result of recent advances and improvements in these approaches.Autonomous cars are one such application.This is expected to have a significant and revolutionary influence on society.Integration with smart cities,new infrastructure and urban planning with sophisticated cyber-security are some of the current ramifications of self-driving automobiles.The autonomous automobile,often known as selfdriving systems or driverless vehicles,is a vehicle that can perceive its surroundings and navigate predetermined routes without human involvement.Cars are on the verge of evolving into autonomous robots,thanks to significant breakthroughs in artificial intelligence and related technologies,and this will have a wide range of socio-economic implications.However,in order for these automobiles to become a reality,they must be endowed with the perception and cognition necessary to deal with high-pressure real-life events and make proper judgments and take appropriate action.The majority of self-driving car technologies are based on computer systems that automate vehicle control parts.From forward-collision warning and antilock brakes to lane-keeping and adaptive drive control,to fully automated driving,these technological components have a wide range of capabilities.A self-driving car combines a wide range of sensors,actuators,and cameras.Recent researches on computer vision and deep learning are used to control autonomous driving systems.For self-driving automobiles,lane-keeping is crucial.This study presents a deep learning approach to obtain the proper steering angle to maintain the robot in the lane.We propose an advanced control for a selfdriving robot by using two controllers simultaneously.Convolutional neural networks(CNNs)are employed,to predict the car’and a proportionalintegral-derivative(PID)controller is designed for speed and steering control.This study uses a Raspberry PI based camera to control the robot car.展开更多
The problem of water supply from the public distribution network still poses very serious problems in many cities in developing countries. Intermittent water supply pushes some households to build underground reinforc...The problem of water supply from the public distribution network still poses very serious problems in many cities in developing countries. Intermittent water supply pushes some households to build underground reinforced concrete tanks for water storage to cope with unwanted water breaks. This study that relies on the results of a survey of households in some areas of the city of Brazzaville (Republic of Congo) aims to verify the importance that users attach to the quality of the works constructed. Indeed, the reliability of the tanks resulting in their impermeability to the external environment has a direct impact on the quality of stored water and therefore the use that is made of water daily. Five areas were selected because of their soil moisture. By 256 tanks identified, 143 are made of reinforced concrete and 113 in masonry. The coating materials used to seal the walls are preferably the earthenware tiles (64% of tanks), then the Sika cement (31%). Food painting (5%) is only rarely used. However, 66% of households are not assured of the potability of the water stored. A significant number of households (46%) think that the stored water could be contaminated with noxious substances seeping from the outside through the walls of the tanks. The issue of sealing of underground water tanks, especially in areas where the water table is shallow, seems concerned users.展开更多
The effect of essential oils from Syzygium aromaticum and Cymbopogon citratus on the lipid oxidation and microbial growth in beef patties was investigated in the present study. Essential oils were incorporated into th...The effect of essential oils from Syzygium aromaticum and Cymbopogon citratus on the lipid oxidation and microbial growth in beef patties was investigated in the present study. Essential oils were incorporated into the beef patties at 0.1% and 0.2% (w/w). The beef patties were then inoculated with cultures of E. coli and S. aureus and stored at 4°C. The control patties were processed without essential oil but inoculated with E. coli or S. aureus. The proximate composition, lipid oxidation and microbial counts were carried out after 7, 14, 21 and 28 days. Results showed that the incorporation of essential oils in beef patties did not significantly (P S. aromaticum at 0.2% reduced the E. coli growth by 1.48 log CFU/g and that of S. aureus by 6.52 log CFU/g while the incorporation of C. citratus at 0.2% reduced the E. coli growth by 1.21 log CFU/g and that of S. aureus by 1.4 log CFU/g after 28 days of storage. The pH measurement during the storage period showed a slight drop during the first 7 days of storage and an increase during the last 21 days in all samples. The sensory test of the beef patties showed that the consumers accepted patties formulated with the two essential oils. But the one made with 0.1% essential oil of S. aromaticum was the most accepted. The analysis of the color of beef patties between 0 and 28 days of storage revealed that the incorporation of essential oils retarded the degradation of the color of patties. Results obtained in the present study indicate the possibility of exploiting Syzygium aromaticum and Cymbopogon citratus essential oils to protect beef patties against lipid oxidation and microbial growth.展开更多
The switched reluctance motor is appreciated in variable speed drives through his simplicity of design, his low cost, his high reliability and high ability to regulate which allow him to compete with the other common ...The switched reluctance motor is appreciated in variable speed drives through his simplicity of design, his low cost, his high reliability and high ability to regulate which allow him to compete with the other common types of electric drives. The mathematical modelling of switched reluctance motors (SRM) allows his study in the areas of research and conception. In this paper, we present the developing of a methodology using the combined model of switched reluctance motor drive bases in standard equations of electrical machines with the field theory analysis of magnetic circuit. Then, the elaboration of mathematical models for switching reluctance motor (SRM) proposes his application based on a similarity with series DC motor to simplify the conception of control of electrical drives systems [1] with Closed Loop Control.展开更多
In this work the authors present a calculation process of the blades for wind turbine with horizontal axis. It is about a blade discretized by the finite element method （FEM） in order to determine the gyroscopic eff...In this work the authors present a calculation process of the blades for wind turbine with horizontal axis. It is about a blade discretized by the finite element method （FEM） in order to determine the gyroscopic effect during its rotation at a high speed. A blade must have the maximum output and resist to aerodynamic loads distributed over its length, which are related to its geometrical characteristics and the speed of the wind. For that, the authors wrote the relations whom determine these loads according to the flow speed of the wind, then, the authors integrated them in the laws of structure mechanics to obtain the motion equations of the blade. This process was applied to a twisted blade with a length of 1.9 m, built out of pressed aluminum sheet with a profile of the type NACA; this profile gives the best aerodynamic output. This blade is an element of a three-bladed propeller for wind turbine of maximum power 5 kW. Finally, we visualized its deformations and then the authors checked its holding in service.展开更多
Some researchers in mechanical engineering have developed systems for the design of gear transmission boxes, but almost no calculation methods exist for widespread synthesis. In this article, we outline methods for au...Some researchers in mechanical engineering have developed systems for the design of gear transmission boxes, but almost no calculation methods exist for widespread synthesis. In this article, we outline methods for automatic determination of toothed helical gear trains and the selection criteria for the optimal choice of gear trains. In this work two methods were applied. As first design to use an expert system for the design and then optimize the design that is why we used Kappa PC and Catia for CAD.展开更多
文摘Many attempts have been made to estimate calorific value of bagasse using mathematical equations, which were created based on data from proximate, ultimate, physical and chemical analysis. Questions have been raised on the applicability of these equations in different parts of the globe. This study was initiated to tackle these problems and also check the most suited mathematical models for the Law Heating Value of Cameroonian bagasse. Data and bagasse samples were collected at the Cameroonian sugarcane factory. The effects of cane variety, age of harvesting, source, moisture content, and sucrose on the LHV of Cameroon bagasse have been tested. It was shown that humidity does not change within a variety, but changes from the dry season to the rainy season;the sugar in the rainy season is significantly different from that collected in the dry season. Samples of the same variety have identical LHV. LHV in the dry season is significantly different from LHV in the rainy season. According to the fact that this study was done for cane with different ages of harvesting, the maturity of Cameroonian sugarcane does not affect LHV of bagasse. Tree selected models are much superior tool for the prediction of the LHV for bagasse in Cameroon compared to others. The standard deviation of these validated models is around 200 kJ/kg compared to the experimental. Thus, the models determined in foreign countries, are not necessarily applicable in predicting the LHV of bagasse in other countries with the same accuracy as that in their native country. There was linear relationship between humidity, ash and sugar content in the bagasse. It is possible to build models based on data from physical composition of bagasse using regression analysis.
文摘The objective of this work is to improve the physical and mechanical properties of stabilized earth blocks (BTC) used in construction in the Ndé department of Cameroon. To achieve this, two stabilizers, cement and sawdust, were used at varying percentages of 0%, 4%, 6%, and 8%. Physical characterization tests, including natural water content, specific weight, jar test, Protor, and Atterberg limits, were conducted. Additionally, mechanical tests, such as compression and three-point bending, were performed. The results show that as the amount of stabilizer increases, the density of BTC decreases. The samples with 8% sawdust have the highest density, while those without stabilizers have the lowest. Porosity decreases as sawdust and cement content increases, with smaller values observed in samples with 8% sawdust or cement. Our tests indicate that blocks stabilized with cement have slightly higher compressive strength than those stabilized with sawdust. However, the water absorption rate increases with higher sawdust content.
文摘The objective of this paper is to evaluate the reliability of a system in its different states (absence of failures, partial failure and total failure) and to propose actions to improve this reliability by an approach based on Monte Carlo simulation. It consists of a probabilistic evaluation based on Markov Chains. In order to achieve this goal, the functionalities of Markov Chains and Monte Carlo simulation steps are deployed. The application is made on a production system. .
文摘Energy is a crucial material for the development of our economy.Access to sufficient energy remains a major concern for developing countries,particularly those in sub-Saharan Africa.The major challenge lies in access to clean,environmentally friendly,quality and low-cost energy in different households in our municipalities.To cope with this vast energy gap,many households are dependent on fossil fuels.In Cameroon,the consumption of wood for the supply of energy is increasing by 4%per year.Overall,approximately 80%of households in Cameroon depend on woody biomass as the sole main source of energy supply in Cameroon and demand is growing over time.In view of the climatic variations that our countries,particularly Cameroon,undergo through deforestation,the use of wood as a source of energy is expensive and harmful to the environment,hence the urgency of replacing wood with renewable energy.Biogas is one of the most versatile sources of renewable energy.On an industrial scale,it is important to automate the process control.The main objective of the present work is to model the anaerobic digestion of coffee and cocoa hulls using the particle swarm optimisation method.Pretreatment using the organosolv process was done.This resulted in 48%lignin removal and 22%cellulose increase.For the pretreated biomass,the maximum production rate was 21 NmLCH4 per day with a biomethane yield of 90 NmLCH4/gVS.This represents an enhancement of 117%in biomethane yield.A positive flammability test was recorded after the 10th day of retention time.Moreover,the data collected during anaerobic digestion allowed implementation of a two-phase mathematical model.The thirteen parameters of the model were estimated with particle swarm optimisation method in Matlab.The model was able to simulate the biomethane production kinetics and variation of volatile fatty acid concentration.
文摘Many physical processes have nonlinear behavior which can be well represented by a polynomial NARX or NARMAX model. The identification of such models has been widely explored in literature. The majority of these approaches are for the open-loop identification. However, for reasons such as safety and production restrictions, open-loop identification cannot always be done. In such cases, closed-loop identification is necessary. This paper presents a two-step approach to closed-loop identification of the polynomial NARX/NARMAX systems with variable structure control （VSC）. First, a genetic algorithm （GA） is used to maximize the similarity of VSC signal to white noise by tuning the switching function parameters. Second, the system is simulated again and its parameters are estimated by an algorithm of the least square （LS） family. Finally, simulation examples are given to show the validity of the proposed approach.
文摘This paper presents a fluoride health risk characterization approach to identify the hyper-sensitive population of adverse effect like tooth decay, dental fluorosis and skeletal fluorosis. In this context, a sampling campaign has been done over 100 Tunisian water consumption points (tap). Laboratory analysis results show that the quality of drinking water is affected by high fluoride concentration level exceeding 2 mg·L-1. Over these samples, 7% of them present non-compliant with the Tunisian national standard (NT09.14) and the international guidelines (World Health Organization recommendations, WHO). The overtake cases are located essentially in southern Tunisian areas, i.e. Medenine, Gabes, Gafsa and Tataouine. One can highlight that groundwater, in these southern Tunisian areas, are naturally rich of fluoride. This is because of the aquifers geological and fossil nature. However, commonly northern and central Tunisian areas are characterized by low fluoride concentration level below 0.1 mg·L-1. These undertaken cases don’t meet the water quality requirement defined by WHO.
文摘The objective of this paper is to develop an efficient P wave detection method in electrocardiogram (ECG) using the local entropy criterion (EC) and wavelet transform (WT) modulus maxima. The detection of P wave relates to the diagnosis of many heart diseases and it is also a difficult point during the ECG signal detection. Determining the position of a P-wave is complicated due to the low amplitude, the ambiguous and changing form of the complex. In a first step, QRS complexes are detected using the pan-Tompkins method. Then, we look for the best position of the analysis window and the value of the most appropriate width to the P wave. Finally, the determination of P wave peaks, as well as their onsets and offsets. The method has been validated using ECG-recordings with a wide variety of P-wave morphologies from MIT-BIH Arrhythmia and QT database. The P-wave method obtains a sensitivity of 99.87% and a positive predictivity of 98.04% over the MIT-BIH Arrhythmia, while for the QT, sensitivity and predictivity over 99.8% are attained.
文摘The sugarcane bagasse fuel is an energetic deposit opportunity for thermal and electricity generation in sugar society.Combustion behaviors,essential for effective operation of these devices are a necessity.A 3D numerical model has been developed in the commercial software Ansys Fluent.According to the fuel density and particle variable,this model took into account both suspension and grate model combustion.The realizable k-ε turbulent model with the P-1 model shows its advantage of describing such king problems and has been applied on the numerical model.The contour of the temperature,spices and the particle trajectory provided a clear understanding of bagasse fuel combustion in the furnace as well,bagasse particle goes through from initial heating to char combustion and its conversion to ash.The results obtained were in accordance with those of the literature.These results could be used to analyze this inexpensive combustion process for looking for the effect of design parameter change on the furnace performance.
文摘An endoreversible model is used to simulate the dynamic behavior of a solar driven absorption refrigerator, the cycle under different operating and design conditions. A global time minimization procedure is performed to reach maximum performances. To evaluate the influence of the cold temperature on the system’s performances, results are carried out for three values of this temperature. They are presented in normalized charts for general applications. The minimum time set point temperature, entropy and maximum refrigeration load are sharp and therefore, are important to be considered for system design.
文摘Aluminium oxide coatings were formed on aluminium substrates in oxalic acid-sulphuric acid bath. Abrasion tests of the obtained anodic layers were carried out on a pin-on-disc machine in accordance with the ISO/DP 825 specifications. The rickets microhardness, D （HV0.2）, and the abrasion weight loss, Wa （mg） were measured. Influence of oxalic acid concentration （Cox）, bath temperature （T） and anodic current density （J） on D and Wa has been examined, and the sulphuric acid concentration （Csul） was maintained at 100 g.L-1. It was found that high microhardness and abrasive wear resistance of oxide layers were produced under low temperatures and high current densities with the addition of oxalic acid. The morphology and the composition of the anodic oxide layer were examined by scanning electron microscopy （SEM）, atomic force microscopy （AFM）, optical microscopy and glow-discharge optical emission spectroscopy （GDOES）. It was found that the chemistry of the anodizing electrolyte, temperature, and current density are the controlling factors of the mechanical properties of the anodic oxide layer.
文摘This article outlines the theoretical and experimental performance studies of a cylindro-parabolic solar collector. The theoretical study consists on the establishment, through mass and energy balances, of a mathematical model to control the exiting temperature of the heating fluid as well as the temperatures of the absorber and the glass. The experimental level investigates the influence of the solar absorber tube diameter on the performances of the driving device. Several experiments were made in order to know the possibility to reach temperatures being able to ensure for example the ammonia vaporization in the generator of a solar absorption refrigeration system. These experiments were carried out under various operating and climatic conditions. The results are presented and discussed.
文摘In this paper, we present a new robust hybrid algorithm combining successively chaotic encryption and blind watermarking of images based on the quaternionic wavelet transform (QWT) to ensure the secure transfer of digital data. The calculations of the different evaluation parameters have been performed in order to determine the robustness of our algorithm to certain attacks. The application of this hybrid algorithm on CFA (Color Filter Array) images, allowed us to guarantee the integrity of the digital data and to propose an autonomous transmission system. The results obtained after simulation of this successive hybrid algorithm of chaotic encryption and then blind watermarking are appreciated through the values of the evaluation parameters which are the peak signal-to-noise ratio (PSNR) and the correlation coefficient (CC), and by the visual observation of the extracted watermarks before and after attacks. The values of these parameters show that this successive hybrid algorithm is robust against some conventional attacks.
文摘The effect of dietary supplementation with mango (Mangifera indica L.) powder obtained by microwave dehydration was studied in normal and hypercholesterolemic mice. The phenolic profiles in methanolic extracts and antioxidant activities were determined using high-performance liquid chromatography and DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2'-azino-bis-3-ethyl-benzothiazoline-6-sulphonic acid) assays, respectively. The total phenolic content of microwave-dehydrated mango powder was 1451.7 ± 26.7 μggallic acid equivalents/g dry weight. The main phenolic compounds identified were gallic acid, epicatechin, ferulic acid, and catechin. The anti-oxidant activity was 14.6% higher in microwave-dehydrated mango powder than in conventional mango powder. Mice were fed a hypercholesterolemic diet (1 g cholesterol/100g over 7 days). The hypercholesterolemic mice whose diets were supplemented with microwave-dehydrated mango powder showed a significant decrease (P ≤ 0.05) in total serum cholesterol compared to the hypercholesterolemic mice and the mice fed with conventional dehydrated mango powder. We observed a significant increase (P ≤ 0.05) in HDL-c levels in the microwave-dehydrated mango powder group mice (12.4 ± 1.3 mmol/L) compared to the hypercholesterolemic group (8.6 ± 1.4 mmol/L) and the conventional-dehydrated mango powder group (10.9 ± 1.3 mmol/L). The mice provided with microwave-dehydrated mango powder had significantly lower (P ≤ 0.05) levels of serum LDL-c (36.0%) and total cholesterol (43.3%) compared to the mice in hypercholesterolemic group. Notably, the atherogenic index was 72% lower in the microwave-dehydrated mango powder group compared to the hypercholesterolemic group. These results suggest that the biocompounds, such as polyphenols and dietary fiber, found in mango pulp might improve the lipid profile in mice fed a hypercholesterolemic diet.
文摘The present study was carried out to evaluate the effect of different rates of dried cassava leafs in diet as replacement of protein sources on the weight gain and carcass yield of guinea-pigs, as well as on the physico-chemical and technological properties of guinea-pigs’ meat. A total of forty-eight (48) eight-week-old guinea-pigs were divided in a completely randomized experimental design, in four groups and fed with the experimental foods. These experimental foods were formulated as follows: cassava-leaf (Manihot esculenta) powder was incorporated at concentrations of 0%, 8%, 10% and 12% respectively in replacement of protein sources for R0, R1, R2 and R3. Each treatment consisted of a group of 12 guinea pigs per paddock (6 males and 6 females). The initial weight (IW), final weight (FW), daily weight gain (DWG) and total gain (TG) were evaluated. At the 22nd week, animals of each group were sacrificed by bleeding, then skinned and eviscerated. Carcasses were cut, and some parts (loin, thigh and shoulder) were collected, deboned and analysed. The highest FW and carcass yield (CY) were obtained with the use of 10% cassava leafs (R2): 556 g (FW), 42.65% (CY) for males and 529.17 g (FW), 37.39% (CY) for females. The incorporation of 8% (R1) and 12% (R3) cassava leafs led to a significant increase (P < 0.05) in protein levels in the loins (22.89%) and shoulders (22.43%) of females and the thighs (21.68%) and shoulders (21.09%) of males. However, protein levels of male fed with R3 in the various parts studied were higher than females fed with the same diet. The study of the technological parameters of guinea-pig’s meat showed that the incorporation of 8% and 12% cassava leafs in the diet resulted in a significant decrease in the water holding capacity and technological yield in the different parts studied. These results show that, the incorporation of cassava leafs in guinea-pigs’ diet made it possible to obtain good growth (R2) and meat of good technological quality.
文摘Several applications of machine learning and artificial intelligence,have acquired importance and come to the fore as a result of recent advances and improvements in these approaches.Autonomous cars are one such application.This is expected to have a significant and revolutionary influence on society.Integration with smart cities,new infrastructure and urban planning with sophisticated cyber-security are some of the current ramifications of self-driving automobiles.The autonomous automobile,often known as selfdriving systems or driverless vehicles,is a vehicle that can perceive its surroundings and navigate predetermined routes without human involvement.Cars are on the verge of evolving into autonomous robots,thanks to significant breakthroughs in artificial intelligence and related technologies,and this will have a wide range of socio-economic implications.However,in order for these automobiles to become a reality,they must be endowed with the perception and cognition necessary to deal with high-pressure real-life events and make proper judgments and take appropriate action.The majority of self-driving car technologies are based on computer systems that automate vehicle control parts.From forward-collision warning and antilock brakes to lane-keeping and adaptive drive control,to fully automated driving,these technological components have a wide range of capabilities.A self-driving car combines a wide range of sensors,actuators,and cameras.Recent researches on computer vision and deep learning are used to control autonomous driving systems.For self-driving automobiles,lane-keeping is crucial.This study presents a deep learning approach to obtain the proper steering angle to maintain the robot in the lane.We propose an advanced control for a selfdriving robot by using two controllers simultaneously.Convolutional neural networks(CNNs)are employed,to predict the car’and a proportionalintegral-derivative(PID)controller is designed for speed and steering control.This study uses a Raspberry PI based camera to control the robot car.
文摘The problem of water supply from the public distribution network still poses very serious problems in many cities in developing countries. Intermittent water supply pushes some households to build underground reinforced concrete tanks for water storage to cope with unwanted water breaks. This study that relies on the results of a survey of households in some areas of the city of Brazzaville (Republic of Congo) aims to verify the importance that users attach to the quality of the works constructed. Indeed, the reliability of the tanks resulting in their impermeability to the external environment has a direct impact on the quality of stored water and therefore the use that is made of water daily. Five areas were selected because of their soil moisture. By 256 tanks identified, 143 are made of reinforced concrete and 113 in masonry. The coating materials used to seal the walls are preferably the earthenware tiles (64% of tanks), then the Sika cement (31%). Food painting (5%) is only rarely used. However, 66% of households are not assured of the potability of the water stored. A significant number of households (46%) think that the stored water could be contaminated with noxious substances seeping from the outside through the walls of the tanks. The issue of sealing of underground water tanks, especially in areas where the water table is shallow, seems concerned users.
文摘The effect of essential oils from Syzygium aromaticum and Cymbopogon citratus on the lipid oxidation and microbial growth in beef patties was investigated in the present study. Essential oils were incorporated into the beef patties at 0.1% and 0.2% (w/w). The beef patties were then inoculated with cultures of E. coli and S. aureus and stored at 4°C. The control patties were processed without essential oil but inoculated with E. coli or S. aureus. The proximate composition, lipid oxidation and microbial counts were carried out after 7, 14, 21 and 28 days. Results showed that the incorporation of essential oils in beef patties did not significantly (P S. aromaticum at 0.2% reduced the E. coli growth by 1.48 log CFU/g and that of S. aureus by 6.52 log CFU/g while the incorporation of C. citratus at 0.2% reduced the E. coli growth by 1.21 log CFU/g and that of S. aureus by 1.4 log CFU/g after 28 days of storage. The pH measurement during the storage period showed a slight drop during the first 7 days of storage and an increase during the last 21 days in all samples. The sensory test of the beef patties showed that the consumers accepted patties formulated with the two essential oils. But the one made with 0.1% essential oil of S. aromaticum was the most accepted. The analysis of the color of beef patties between 0 and 28 days of storage revealed that the incorporation of essential oils retarded the degradation of the color of patties. Results obtained in the present study indicate the possibility of exploiting Syzygium aromaticum and Cymbopogon citratus essential oils to protect beef patties against lipid oxidation and microbial growth.
文摘The switched reluctance motor is appreciated in variable speed drives through his simplicity of design, his low cost, his high reliability and high ability to regulate which allow him to compete with the other common types of electric drives. The mathematical modelling of switched reluctance motors (SRM) allows his study in the areas of research and conception. In this paper, we present the developing of a methodology using the combined model of switched reluctance motor drive bases in standard equations of electrical machines with the field theory analysis of magnetic circuit. Then, the elaboration of mathematical models for switching reluctance motor (SRM) proposes his application based on a similarity with series DC motor to simplify the conception of control of electrical drives systems [1] with Closed Loop Control.
文摘In this work the authors present a calculation process of the blades for wind turbine with horizontal axis. It is about a blade discretized by the finite element method （FEM） in order to determine the gyroscopic effect during its rotation at a high speed. A blade must have the maximum output and resist to aerodynamic loads distributed over its length, which are related to its geometrical characteristics and the speed of the wind. For that, the authors wrote the relations whom determine these loads according to the flow speed of the wind, then, the authors integrated them in the laws of structure mechanics to obtain the motion equations of the blade. This process was applied to a twisted blade with a length of 1.9 m, built out of pressed aluminum sheet with a profile of the type NACA; this profile gives the best aerodynamic output. This blade is an element of a three-bladed propeller for wind turbine of maximum power 5 kW. Finally, we visualized its deformations and then the authors checked its holding in service.
文摘Some researchers in mechanical engineering have developed systems for the design of gear transmission boxes, but almost no calculation methods exist for widespread synthesis. In this article, we outline methods for automatic determination of toothed helical gear trains and the selection criteria for the optimal choice of gear trains. In this work two methods were applied. As first design to use an expert system for the design and then optimize the design that is why we used Kappa PC and Catia for CAD.
