This work presents the physical and thermal characterization of the dura palm kernel powder of Cameroon for their use as fillers for polymers composites. The powders of palm kernel were obtained using a percussion gri...This work presents the physical and thermal characterization of the dura palm kernel powder of Cameroon for their use as fillers for polymers composites. The powders of palm kernel were obtained using a percussion grinder mill with an industrial microniser which allowed obtaining a powder less than 50 μm with an apparent density between 0,505 ≤ ρ ≤ 0,680 g/cm3 at 1.56 of relative humidity. The infrared of the powder of palm kernel shows the presence of phenols groups with a large band around 3341 cm-1, -C-H at 2917.02 cm-1 and -C-O at 1040 cm-1 as the main peaks. The polyvinyl chloride of infrared obtained shows the presence of -C-Cl, -CH2 and CH as the mains peaks. The infrared of 12.5% of palm kernel powder with polyvinyl chloride shows an increase of the CH2 and CH bonds and a decrease of the -OH bonds. Thermogravimetric analysis and differential scanning calorimetric analysis of powders, polyvinyl chloride and mixture showed that the mixing powders are intermediate between the polyvinyl chloride and palm kernel powder. The powder decreased the phase temperatures of the mixture from 98.58℃ to 95℃ for the glass transition temperature and from 515℃ to 459℃ for the crystallization temperature. The thermogravimetric curves of palm kernel powder and polyvinyl chloride have showed that these materials lose their different masses in three different phases, and the one of composite (mixture of polyvinyl chloride with 12.5% of palm kernel powder) in two different phases.展开更多
The Computational Fluid Dynamics (CFD) have been used in the analysis and design of agitated vessel. Most of the researches done in this area are limited to the baffled or unbaffled stirred tank. In this paper, we hav...The Computational Fluid Dynamics (CFD) have been used in the analysis and design of agitated vessel. Most of the researches done in this area are limited to the baffled or unbaffled stirred tank. In this paper, we have been interested in studying of the new design. Particularly, the flow and turbulence fields in square vessel stirred by a standard Rushton turbine have been simulated by means of CFD techniques. The Navier-Stokes equations governing the phenomenon of transfer of momentum are solved by a discretization method for finite volume. The MRF approaches can be used in simulation of the steady state problem. The numerical results from the application of CFD code Fluent with the stationary approach Multi Reference Frame (MRF) are presented in the planes containing the blade. The validation of CFD results with experimental measurements showed a good agreement.展开更多
Model-Based Design is an efficient and cost-effective way to develop controls, signal processing, image processing, communications, mechatronics, and other embedded systems. Rather than re-lying on physical prototypes...Model-Based Design is an efficient and cost-effective way to develop controls, signal processing, image processing, communications, mechatronics, and other embedded systems. Rather than re-lying on physical prototypes and textual specifications, Model-Based Design uses a system model as an executable specification throughout development. It supports system- and component-level design and simulation, automatic code generation, and continuous test and verification. This paper is focused firstly on the so-called model-based design and aims at presenting an up-to-date state of the art in this important field. Secondly, it develops a model based design for wind energy systems. Mathematical formulations and numerical implementations for different components of wind energy systems are highlighted with Simscape language. Finally, results are derived from simulations.展开更多
This present issue is an extension of the work of Y. Xiao-Zhong et al. who investigated the influence of constant external magnetic field on the decoherence of a central electron spin of atom coupled to an anti-ferrom...This present issue is an extension of the work of Y. Xiao-Zhong et al. who investigated the influence of constant external magnetic field on the decoherence of a central electron spin of atom coupled to an anti-ferromagnetic environment. We have shown in this work that the character variability of the field induces oscillations amongst the eigen modes of the environment. This observation is made via the derivation of the transition probability density of state, a manner by which critical parameters (parameters where transition occur) of the system could be obtained as it shows resonance peak. We equally observed that the two different magnons modes resulting from the frequency splitting via the application of the time-varying external B-Field, exhibit each a resonant peak of similar amplitude at different temperature ranges. This additional information shows that the probability for the central spin system to remain in its initially prepared diabatic state is enhanced for some temperature ranges for the corresponding two magnon modes. Hence, these temperature ranges where the probability density is maximum could save as decoherence free environment;an important requirement for the implementation of quantum computation and information processing in solid state circuitry. The theoretical and numerical results presented for the decoherence time and the probability density are that of a decohered central electron spin coupled to an anti-ferromagnetic spin bath. The theory is based on a spin wave approximation and on the density matrix using both transformations of Bloch, Primakov and Bogoliobuv in the adiabatic limit.展开更多
High-Density Polyethylene(HDPE)wear debris generated in the hip joint prothesis leads to its loosening.The aim of this study was to evaluate the potential of Squid Pen(SP)on the tribological and physicochemical proper...High-Density Polyethylene(HDPE)wear debris generated in the hip joint prothesis leads to its loosening.The aim of this study was to evaluate the potential of Squid Pen(SP)on the tribological and physicochemical properties of HDPE matrix.Biocomposites filled with 0,5,10,15 and 20 wt.%SP were elaborated by hot compression molding.Wear tests were carried out using a reciprocating pin-on-disc tribometer.Rockwell hardness,Fourier-Transform infra-red(FTIR)analysis,Scanning Electron Microscopy(SEM)of the biocomposite were analysed.FTIR analysis results of the biocomposites showed that an increase in the crystallinity rate was obtained with the addition of SP filler.Only 10 wt.%of SP has a significant effect on the hardness of the composite.The correlation between the friction coefficient and the wear resistance of the composite was investigated.The 5 wt.%SP-HDPE biocomposite has the lowest friction coefficient value with a decrease in the specific wear rate,compared to the unfilled HDPE.The SEM results showed that SP wear debris played an important role as a third roller body at the interface reducing the friction coefficient of the composite.It was concluded that the HDPE biocomposite could be successfully reinforced with 5 wt.%of SP.展开更多
A feasibility study has been carried out on a high altitude (20km) superpressurcd PLTA(powered lighter-than-air) platform, which has a long service life and larger payload than that of a large artificial satellite. Th...A feasibility study has been carried out on a high altitude (20km) superpressurcd PLTA(powered lighter-than-air) platform, which has a long service life and larger payload than that of a large artificial satellite. This PLTA platform has an electric propulsion system to cope with wind flow for position keeping and its thruster is driven by solar power acquired through solar cells. Solar energy is to be stored for night use in regenerative fuel cells. The study is focused on energy balance and hull structure analysis of the platform. This platform is particularly capable of conducting high resolution remote sensing and telecommunications relay. This platform can replace a number of ground-based telecommunications relay facilities and can guarantee reasonable radio frequency intensity enough to secure good telecommunications quality. The altitude where the platform resides is the least windy area in the lower stratosphere at a height from which one can have a direct line of sight on the ground within a 1,000km diameter range. The platform can also be useful to chase typhoons and to observe them from their births in the tropical regions.展开更多
Hardware in the loop simulation （HILS） has been investigated in the field of the multibody dynamics （MBD）, which combined the MBD simulation with the actual mechanical system. The fast simulation is necessary for ...Hardware in the loop simulation （HILS） has been investigated in the field of the multibody dynamics （MBD）, which combined the MBD simulation with the actual mechanical system. The fast simulation is necessary for the HILS system in order to require the real time simulation. This paper presents a fast simulation technique using the domain decomposition method with the iteration in the flexible multibody system in which flexible linkage system and electro-hydraulic drive system are coupled with each other. C 2013 The Chinese Society of Theoretical and Applied Mechanics.[doi：10.1063/2.1301301]展开更多
The constant increase in energy demand and related environmental issues have made fuel cells an attractive technology as an alternative to conventional energy technologies.Like any technology,fuel cells face drawbacks...The constant increase in energy demand and related environmental issues have made fuel cells an attractive technology as an alternative to conventional energy technologies.Like any technology,fuel cells face drawbacks that scientific society has been focused on to improve and optimize the overall technology.Thus,the cost is the main inhibitor for this technology due to the significantly high cost of the materials used in catalyst layers.The current discussion mainly focuses on the fundamental electrochemical half-cell reaction of hydrogen oxidation reaction(HOR)and oxygen reduction reaction(ORR)that are taking place in the catalyst layers consisting of Platinum-based and Platinum-non noble metals.For this purpose,studies from the literature are presented and analyzed by highlighting and comparing the variations on the catalytic activity within the experimental catalyst layers and the conventional ones.Furthermore,an economic analysis of the main platinum group metals(PGMs)such as Platinum,Palladium and Ruthenium is introduced by presenting the economic trends for the last decade.展开更多
In this paper, a numerical study of a buried hemispherical double-pipe heat exchanger with soil by using geothermal energy is presented. Since the local air-wall exchange coefficient throughout the heat exchanger is u...In this paper, a numerical study of a buried hemispherical double-pipe heat exchanger with soil by using geothermal energy is presented. Since the local air-wall exchange coefficient throughout the heat exchanger is unknown, a study of mathematics based on the theory of Green’s functions in the unsteady state was developed. The complexity of the geometry has led us to develop a numerical study that allows us to obtain results that reflect the importance of heat exchange. The applications are numerous, especially in the storage of energy in the soil to optimize greenhouses according to the cycle of the seasons.展开更多
In the present study the first 20 microatoms of the periodic table are named as bioatoms, since they are needed for biochemical functions and services to life itself. The rationale behind this project is the detailed ...In the present study the first 20 microatoms of the periodic table are named as bioatoms, since they are needed for biochemical functions and services to life itself. The rationale behind this project is the detailed analysis of the ionization energy of the electrons in the inside of the bioatoms and their orderly arrangement at specific positions. Such position of the electrons is harmonized with the succession of their energy values in their logarithmic curves. The compelling arrangement of each electron at a particular place would not be feasible in the absence of an energy offset, which is a proton. The latter would hold electrons on their proper position. These fundamental aspects of our project receive such strong support from the quantum theory, according to which it is the electromagnetic interaction between electrons and protons by the exchange of photons, which hold them together in the atoms. According to our proposed model, the protons of the aforementioned proton—electron twins, are distributed on distinct positions which are the junctions of a primary network, coupled with their electrons, in a secondary network. The geometry and distance of the protons, in the plexus, is constant and is calculated at 8, 42 ?. This was estimated by a mathematical analysis of the proposed model, as discussed further. Our study has shown that electrons in the specific positions are moving in a symmetrical oscillation in the length of a channel, in vacuum, under the Coulomb forces. Moreover, the chemical evidence suggests that electrons, in an atom, have their own separate orbit, and that these orbits are closely interrelated.展开更多
RECYTRACK is a 3.5 year project granted by the European Commission through LIFE＋ 2010 program. The overall objective of the project is to demonstrate the environmental benefits and technical feasibility of the implem...RECYTRACK is a 3.5 year project granted by the European Commission through LIFE＋ 2010 program. The overall objective of the project is to demonstrate the environmental benefits and technical feasibility of the implementation of an elastomeric eco-friendly material made of end-of-life tires with resin for railway applications. Within the project, AV Ingenieros jointly with LEAM, carries out the study of the vibration behavior of the eco-friendly material, which will be applied as a mat for ballasted tracks as well as an isolated block system for slab tracks. Firstly, an analytical model capable to predict the efficiency of the eco-friendly material as a vibration mitigation measure has been developed. Subsequently, and after the implementation of the eco-friendly solutions in real railway infrastructures, its vibration behavior will be measured and validated through in situ measurements during regular service. In this paper the analytical model is defined, the elastomeric material dynamic experimental characterization is described and the under ballast mat Insertion Loss is calculated for two different soil stiffness.展开更多
We present in this work how to use the dura palm kernel shell powders as loads for the elaboration by extrusion of PVC tubes. The transformation of dura palm kernel shells into micronized shell powder as well as its c...We present in this work how to use the dura palm kernel shell powders as loads for the elaboration by extrusion of PVC tubes. The transformation of dura palm kernel shells into micronized shell powder as well as its characterization was the subject of recent work. We carried out, the formulations by using the industrial scales of precision, the mixtures of the instrants with an industrial machine of mark HENSHLLE N˚2 MAIN 570762, the routine tests by ATG/DSC then by IRTF, the extrusion of the tubes with an extruder twin-screw with 9 rooms of transformation finally the tests of conformity by the observations and the analyses. We obtained for the formulations the dosage of 0%, 4.01%, 12.54%, 23.03%, 32.01%, 38.01%, 51.02% representing the percentage of hull powder in the mixture, the machine mixing gave perfectly homogeneous powders, the routine tests showed that the hull powder keeps all its properties until the end of the shaping whatever the percentage of hulls contained in the PVC, the extrusion gave tubes for each formulation and the conformity tests gave perfectly round tubes of diameter 90 × 82 mm, a coloration going from white grey at 0% to dark black at 51.02% showing the influence of the carbon black and the color of the shell powder according to its proportion. The infrared of the tubes obtained shows for each formulation a variation of the CH<sub>2</sub> and CH bonds and a decrease of the −OH bonds. The thermogravimetric analyses and the differential calorimetric analyses of the tubes of each formulation, show each time that the quantity of shell powders in the mixture influences the PVC tubes obtained. Thus, we obtain a variation of the phase temperatures according to the dosage, giving from 108.72<span style="white-space:normal;">˚</span>C to 76.56<span style="white-space:normal;">˚</span>C for the glass transition temperature and from 494.71<span style="white-space:normal;">˚</span>C to 414.56<span style="white-space:normal;">˚</span>C for the melting temperature, at the DSC and a progressive decrease of the mass following the heat absorption with each time 4 phases instead of 5 for the unloaded PVC tubes at the ATG according to the dosage.展开更多
The aim of this study is to characterize physically and mechanically a polyester/fiber palm petiole composite material. This work made it possible to provide the local database of composite materials but also to devel...The aim of this study is to characterize physically and mechanically a polyester/fiber palm petiole composite material. This work made it possible to provide the local database of composite materials but also to develop agricultural waste. According to BSI 2782 standard three formulations [A (10% fiber, 90% polyester);B (20% fiber, 80% polyester) and C (30% fiber, 70% po</span><span style="font-family:Verdana;">lyester)]. Water Absorption rate, density, compressive and three points</span><span style="font-family:Verdana;"> bending tests are carried out on the samples obtained by the contact molding method for each formulation. The material composite obtained by adding fibers from palm oil petiole has a density of 17.98% lower than the one made of pure polyester. Fiber reinforcement rate has no impact on the density of the composite. Formulation A most absorbs water while formulation C has good tensile/compression characteristics and the greatest breaking stress in bending among the three formulations.展开更多
The running-in phase is the first stage of the bearing lifespan. However, this phase is very short and extremely important for the future lifespan of the rolling bearing because it is what sets the stabilized state in...The running-in phase is the first stage of the bearing lifespan. However, this phase is very short and extremely important for the future lifespan of the rolling bearing because it is what sets the stabilized state in terms of roughness of the parts in contact, residual geometry and surface residual stresses, which are key factors in the fatigue resistance of mechanical parts. Several numerical and experimental studies have highlighted the importance of the running-in phase in two scales (macroscopic, meso and microscopic). Due to its high flexibility, the approach presented in this work is a numerical modeling of the running-in phase which has been based on the Weibull distribution. The obtained results confirm the importance of the running-in phase on the lifespan of bearings or other mechanism whose functioning requires an adaptation phase of parts in contact. It also concludes that if the running-in phase has been performed correctly, there is a marked improvement in reliability. The curves describe the useful saved time of lifespan according to the scale of the running-in phase.展开更多
The aim of this study is to contribute to the mastery of the physical characteristics of lateritic soils in order to improve their use for the manufacture of Compressed Stabilized Earth Bricks (CSEB) in the province o...The aim of this study is to contribute to the mastery of the physical characteristics of lateritic soils in order to improve their use for the manufacture of Compressed Stabilized Earth Bricks (CSEB) in the province of North Kivu in the Democratic Republic of Congo (DRC). The study of the physical characteristics of lateritic soils was carried out. Samples were subjected to experimental identification tests on the physical characteristics (water content, density characteristics, particle size distribution and consistency). The results of the laboratory analysis of soil samples show that the water content varies between 5.4% and 36.99%. The density of the solid grains has an arithmetic mean of 2.5 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">. The apparent density varies from 0.83 to 1.35 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">. As for the dry density, it is in the range of 0.61 to 1.25 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">. These relatively low densities indicate that the material studied ha</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">s</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> a significant degree of deformability. From the particle size analysis, it appears that the material studied contain</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">s</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> an important fraction of fine particles. According to the consistency study, the soils studied are plastic clay as Ap class according to the Central Laboratory for Roads and Bridges (CLRB) geotechnical classification system. The particle size curves of the studied samples are within the preferential range of good soils for the manufacture of CSEB. The points representing the studied samples are within the preferential plasticity range of good soils for the manufacture of CSEB. From the above parameters, it appears that the studied material is well adapted for the manufacture of the Compressed Stabilized Earth Bricks</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.展开更多
The environmental effects of hydrokinetic turbines are still under investigation,reflecting the emerging status of this technology.This study investigates the interaction between hydrokinetic rotor wakes and fish swim...The environmental effects of hydrokinetic turbines are still under investigation,reflecting the emerging status of this technology.This study investigates the interaction between hydrokinetic rotor wakes and fish swimming,revealing insights into fish biomechanics in complex flows and assessing the environ-mental implications of marine energy solutions.We conducted numerical simulations with the URANS approach and k−ω−SST turbulence closuremodeltopredictthree-dimensionalturbulent flowinthe OpenFOAM software.The hydrokinetic rotor wake was simulated employing the actuator line method,providing a computationally efficient alternative to full geometry simulations.For accurate replication of the motion of a fish-like tuna(Thunnus atlanticus),dynamic adaptive mesh discretization was employed.The results offer a comparative analysis of fish swimming performance within the wake rotor,particularly when immersed in the tip blade vortex,contrasted with scenarios where fish swim in undisturbed flow conditions.The analysis encompasses three-dimensional wake structures,force generation,efficiency,and equilibrium states(balancing drag and thrust)across varying Swimming numbers(Sw).Key findings in-clude the enhanced attachment of the leading-edge vortex due to the caudal fin’s interaction with the tip blade vortex,resulting in improved auto-propulsive force production;a reduced tail stride frequency observed in fish swimming downstream of the rotor to achieve longitudinal force balance compared to unperturbed flow;and transverse hydrodynamic forces pushing fish radially away from the wake’s influ-ence zone,potentially mitigating the risk of collision with turbine blades.展开更多
In this article,a new method has been presented for the estimation of fracture toughness in brittle materials,which enjoys improved accuracy and reduced costs associated with fracture toughness testing procedure compa...In this article,a new method has been presented for the estimation of fracture toughness in brittle materials,which enjoys improved accuracy and reduced costs associated with fracture toughness testing procedure compared to similar previous methods,because a vast range of specimens with irregular cracks can be accommodated for testing.Micron-sized alumina powders containing 0.05 wt%magnesium oxide(MgO)nanoparticles were mixed and also together with 2.5 vol%,5 vol%,7.5 vol%,10 vol%,and 15 vol%of silicon carbide(SiC)nanopowders separately.By making and testing various types of ceramics with different mechanical properties,and considering the irregular cracks around the indented area caused by Vickers diamond indenter,a semi-empirical fracture toughness equation has been obtained.展开更多
Developing versatile and robust surfaces that mimic the skins of living beings to regulate air/liquid/solid matter is critical for many bioinspired applications.Despite notable achievements,such as in the case of deve...Developing versatile and robust surfaces that mimic the skins of living beings to regulate air/liquid/solid matter is critical for many bioinspired applications.Despite notable achievements,such as in the case of developing robust superhydrophobic surfaces,it remains elusive to realize simultaneously topology-specific superwettability and multipronged durability owing to their inherent tradeoff and the lack of a scalable fabrication method.Here,we present a largely unexplored strategy of preparing an all-perfluoropolymer(Teflon),nonlinear stability-assisted monolithic surface for efficient regulating matters.展开更多
It is well known that the ambient temperature is a sensitive parameter which has a great effect on biology, technology, geology and even on human behavior. A prediction is a statement about an uncertain event. It is o...It is well known that the ambient temperature is a sensitive parameter which has a great effect on biology, technology, geology and even on human behavior. A prediction is a statement about an uncertain event. It is often, but not always, based upon experience or knowl- edge. Although guaranteed accurate information about the future is in many cases impossible, prediction can be useful to assist in making plans about possible developments. As a result, temperature profiles can be developed which accurately represent the expected ambient temperature exposure that this environment experiences during mea- surement. The ambient temperature over time is modeled based on the previous Train and Tmax data and using a Lagrange interpolation. To observe the comprehensive variation of ambient temperature the profile must be determined numerically. The model proposed in this paper can provide an acceptable way to measure the change in ambient temperature.展开更多
文摘This work presents the physical and thermal characterization of the dura palm kernel powder of Cameroon for their use as fillers for polymers composites. The powders of palm kernel were obtained using a percussion grinder mill with an industrial microniser which allowed obtaining a powder less than 50 μm with an apparent density between 0,505 ≤ ρ ≤ 0,680 g/cm3 at 1.56 of relative humidity. The infrared of the powder of palm kernel shows the presence of phenols groups with a large band around 3341 cm-1, -C-H at 2917.02 cm-1 and -C-O at 1040 cm-1 as the main peaks. The polyvinyl chloride of infrared obtained shows the presence of -C-Cl, -CH2 and CH as the mains peaks. The infrared of 12.5% of palm kernel powder with polyvinyl chloride shows an increase of the CH2 and CH bonds and a decrease of the -OH bonds. Thermogravimetric analysis and differential scanning calorimetric analysis of powders, polyvinyl chloride and mixture showed that the mixing powders are intermediate between the polyvinyl chloride and palm kernel powder. The powder decreased the phase temperatures of the mixture from 98.58℃ to 95℃ for the glass transition temperature and from 515℃ to 459℃ for the crystallization temperature. The thermogravimetric curves of palm kernel powder and polyvinyl chloride have showed that these materials lose their different masses in three different phases, and the one of composite (mixture of polyvinyl chloride with 12.5% of palm kernel powder) in two different phases.
文摘The Computational Fluid Dynamics (CFD) have been used in the analysis and design of agitated vessel. Most of the researches done in this area are limited to the baffled or unbaffled stirred tank. In this paper, we have been interested in studying of the new design. Particularly, the flow and turbulence fields in square vessel stirred by a standard Rushton turbine have been simulated by means of CFD techniques. The Navier-Stokes equations governing the phenomenon of transfer of momentum are solved by a discretization method for finite volume. The MRF approaches can be used in simulation of the steady state problem. The numerical results from the application of CFD code Fluent with the stationary approach Multi Reference Frame (MRF) are presented in the planes containing the blade. The validation of CFD results with experimental measurements showed a good agreement.
文摘Model-Based Design is an efficient and cost-effective way to develop controls, signal processing, image processing, communications, mechatronics, and other embedded systems. Rather than re-lying on physical prototypes and textual specifications, Model-Based Design uses a system model as an executable specification throughout development. It supports system- and component-level design and simulation, automatic code generation, and continuous test and verification. This paper is focused firstly on the so-called model-based design and aims at presenting an up-to-date state of the art in this important field. Secondly, it develops a model based design for wind energy systems. Mathematical formulations and numerical implementations for different components of wind energy systems are highlighted with Simscape language. Finally, results are derived from simulations.
文摘This present issue is an extension of the work of Y. Xiao-Zhong et al. who investigated the influence of constant external magnetic field on the decoherence of a central electron spin of atom coupled to an anti-ferromagnetic environment. We have shown in this work that the character variability of the field induces oscillations amongst the eigen modes of the environment. This observation is made via the derivation of the transition probability density of state, a manner by which critical parameters (parameters where transition occur) of the system could be obtained as it shows resonance peak. We equally observed that the two different magnons modes resulting from the frequency splitting via the application of the time-varying external B-Field, exhibit each a resonant peak of similar amplitude at different temperature ranges. This additional information shows that the probability for the central spin system to remain in its initially prepared diabatic state is enhanced for some temperature ranges for the corresponding two magnon modes. Hence, these temperature ranges where the probability density is maximum could save as decoherence free environment;an important requirement for the implementation of quantum computation and information processing in solid state circuitry. The theoretical and numerical results presented for the decoherence time and the probability density are that of a decohered central electron spin coupled to an anti-ferromagnetic spin bath. The theory is based on a spin wave approximation and on the density matrix using both transformations of Bloch, Primakov and Bogoliobuv in the adiabatic limit.
基金The authors aregrateful to the University of Monastir and the Ministry of Higher Education and Scientific Research Tunisia for their support(LGM:LAB-MA-05).
文摘High-Density Polyethylene(HDPE)wear debris generated in the hip joint prothesis leads to its loosening.The aim of this study was to evaluate the potential of Squid Pen(SP)on the tribological and physicochemical properties of HDPE matrix.Biocomposites filled with 0,5,10,15 and 20 wt.%SP were elaborated by hot compression molding.Wear tests were carried out using a reciprocating pin-on-disc tribometer.Rockwell hardness,Fourier-Transform infra-red(FTIR)analysis,Scanning Electron Microscopy(SEM)of the biocomposite were analysed.FTIR analysis results of the biocomposites showed that an increase in the crystallinity rate was obtained with the addition of SP filler.Only 10 wt.%of SP has a significant effect on the hardness of the composite.The correlation between the friction coefficient and the wear resistance of the composite was investigated.The 5 wt.%SP-HDPE biocomposite has the lowest friction coefficient value with a decrease in the specific wear rate,compared to the unfilled HDPE.The SEM results showed that SP wear debris played an important role as a third roller body at the interface reducing the friction coefficient of the composite.It was concluded that the HDPE biocomposite could be successfully reinforced with 5 wt.%of SP.
文摘A feasibility study has been carried out on a high altitude (20km) superpressurcd PLTA(powered lighter-than-air) platform, which has a long service life and larger payload than that of a large artificial satellite. This PLTA platform has an electric propulsion system to cope with wind flow for position keeping and its thruster is driven by solar power acquired through solar cells. Solar energy is to be stored for night use in regenerative fuel cells. The study is focused on energy balance and hull structure analysis of the platform. This platform is particularly capable of conducting high resolution remote sensing and telecommunications relay. This platform can replace a number of ground-based telecommunications relay facilities and can guarantee reasonable radio frequency intensity enough to secure good telecommunications quality. The altitude where the platform resides is the least windy area in the lower stratosphere at a height from which one can have a direct line of sight on the ground within a 1,000km diameter range. The platform can also be useful to chase typhoons and to observe them from their births in the tropical regions.
文摘Hardware in the loop simulation （HILS） has been investigated in the field of the multibody dynamics （MBD）, which combined the MBD simulation with the actual mechanical system. The fast simulation is necessary for the HILS system in order to require the real time simulation. This paper presents a fast simulation technique using the domain decomposition method with the iteration in the flexible multibody system in which flexible linkage system and electro-hydraulic drive system are coupled with each other. C 2013 The Chinese Society of Theoretical and Applied Mechanics.[doi：10.1063/2.1301301]
文摘The constant increase in energy demand and related environmental issues have made fuel cells an attractive technology as an alternative to conventional energy technologies.Like any technology,fuel cells face drawbacks that scientific society has been focused on to improve and optimize the overall technology.Thus,the cost is the main inhibitor for this technology due to the significantly high cost of the materials used in catalyst layers.The current discussion mainly focuses on the fundamental electrochemical half-cell reaction of hydrogen oxidation reaction(HOR)and oxygen reduction reaction(ORR)that are taking place in the catalyst layers consisting of Platinum-based and Platinum-non noble metals.For this purpose,studies from the literature are presented and analyzed by highlighting and comparing the variations on the catalytic activity within the experimental catalyst layers and the conventional ones.Furthermore,an economic analysis of the main platinum group metals(PGMs)such as Platinum,Palladium and Ruthenium is introduced by presenting the economic trends for the last decade.
文摘In this paper, a numerical study of a buried hemispherical double-pipe heat exchanger with soil by using geothermal energy is presented. Since the local air-wall exchange coefficient throughout the heat exchanger is unknown, a study of mathematics based on the theory of Green’s functions in the unsteady state was developed. The complexity of the geometry has led us to develop a numerical study that allows us to obtain results that reflect the importance of heat exchange. The applications are numerous, especially in the storage of energy in the soil to optimize greenhouses according to the cycle of the seasons.
文摘In the present study the first 20 microatoms of the periodic table are named as bioatoms, since they are needed for biochemical functions and services to life itself. The rationale behind this project is the detailed analysis of the ionization energy of the electrons in the inside of the bioatoms and their orderly arrangement at specific positions. Such position of the electrons is harmonized with the succession of their energy values in their logarithmic curves. The compelling arrangement of each electron at a particular place would not be feasible in the absence of an energy offset, which is a proton. The latter would hold electrons on their proper position. These fundamental aspects of our project receive such strong support from the quantum theory, according to which it is the electromagnetic interaction between electrons and protons by the exchange of photons, which hold them together in the atoms. According to our proposed model, the protons of the aforementioned proton—electron twins, are distributed on distinct positions which are the junctions of a primary network, coupled with their electrons, in a secondary network. The geometry and distance of the protons, in the plexus, is constant and is calculated at 8, 42 ?. This was estimated by a mathematical analysis of the proposed model, as discussed further. Our study has shown that electrons in the specific positions are moving in a symmetrical oscillation in the length of a channel, in vacuum, under the Coulomb forces. Moreover, the chemical evidence suggests that electrons, in an atom, have their own separate orbit, and that these orbits are closely interrelated.
文摘RECYTRACK is a 3.5 year project granted by the European Commission through LIFE＋ 2010 program. The overall objective of the project is to demonstrate the environmental benefits and technical feasibility of the implementation of an elastomeric eco-friendly material made of end-of-life tires with resin for railway applications. Within the project, AV Ingenieros jointly with LEAM, carries out the study of the vibration behavior of the eco-friendly material, which will be applied as a mat for ballasted tracks as well as an isolated block system for slab tracks. Firstly, an analytical model capable to predict the efficiency of the eco-friendly material as a vibration mitigation measure has been developed. Subsequently, and after the implementation of the eco-friendly solutions in real railway infrastructures, its vibration behavior will be measured and validated through in situ measurements during regular service. In this paper the analytical model is defined, the elastomeric material dynamic experimental characterization is described and the under ballast mat Insertion Loss is calculated for two different soil stiffness.
文摘We present in this work how to use the dura palm kernel shell powders as loads for the elaboration by extrusion of PVC tubes. The transformation of dura palm kernel shells into micronized shell powder as well as its characterization was the subject of recent work. We carried out, the formulations by using the industrial scales of precision, the mixtures of the instrants with an industrial machine of mark HENSHLLE N˚2 MAIN 570762, the routine tests by ATG/DSC then by IRTF, the extrusion of the tubes with an extruder twin-screw with 9 rooms of transformation finally the tests of conformity by the observations and the analyses. We obtained for the formulations the dosage of 0%, 4.01%, 12.54%, 23.03%, 32.01%, 38.01%, 51.02% representing the percentage of hull powder in the mixture, the machine mixing gave perfectly homogeneous powders, the routine tests showed that the hull powder keeps all its properties until the end of the shaping whatever the percentage of hulls contained in the PVC, the extrusion gave tubes for each formulation and the conformity tests gave perfectly round tubes of diameter 90 × 82 mm, a coloration going from white grey at 0% to dark black at 51.02% showing the influence of the carbon black and the color of the shell powder according to its proportion. The infrared of the tubes obtained shows for each formulation a variation of the CH<sub>2</sub> and CH bonds and a decrease of the −OH bonds. The thermogravimetric analyses and the differential calorimetric analyses of the tubes of each formulation, show each time that the quantity of shell powders in the mixture influences the PVC tubes obtained. Thus, we obtain a variation of the phase temperatures according to the dosage, giving from 108.72<span style="white-space:normal;">˚</span>C to 76.56<span style="white-space:normal;">˚</span>C for the glass transition temperature and from 494.71<span style="white-space:normal;">˚</span>C to 414.56<span style="white-space:normal;">˚</span>C for the melting temperature, at the DSC and a progressive decrease of the mass following the heat absorption with each time 4 phases instead of 5 for the unloaded PVC tubes at the ATG according to the dosage.
文摘The aim of this study is to characterize physically and mechanically a polyester/fiber palm petiole composite material. This work made it possible to provide the local database of composite materials but also to develop agricultural waste. According to BSI 2782 standard three formulations [A (10% fiber, 90% polyester);B (20% fiber, 80% polyester) and C (30% fiber, 70% po</span><span style="font-family:Verdana;">lyester)]. Water Absorption rate, density, compressive and three points</span><span style="font-family:Verdana;"> bending tests are carried out on the samples obtained by the contact molding method for each formulation. The material composite obtained by adding fibers from palm oil petiole has a density of 17.98% lower than the one made of pure polyester. Fiber reinforcement rate has no impact on the density of the composite. Formulation A most absorbs water while formulation C has good tensile/compression characteristics and the greatest breaking stress in bending among the three formulations.
文摘The running-in phase is the first stage of the bearing lifespan. However, this phase is very short and extremely important for the future lifespan of the rolling bearing because it is what sets the stabilized state in terms of roughness of the parts in contact, residual geometry and surface residual stresses, which are key factors in the fatigue resistance of mechanical parts. Several numerical and experimental studies have highlighted the importance of the running-in phase in two scales (macroscopic, meso and microscopic). Due to its high flexibility, the approach presented in this work is a numerical modeling of the running-in phase which has been based on the Weibull distribution. The obtained results confirm the importance of the running-in phase on the lifespan of bearings or other mechanism whose functioning requires an adaptation phase of parts in contact. It also concludes that if the running-in phase has been performed correctly, there is a marked improvement in reliability. The curves describe the useful saved time of lifespan according to the scale of the running-in phase.
文摘The aim of this study is to contribute to the mastery of the physical characteristics of lateritic soils in order to improve their use for the manufacture of Compressed Stabilized Earth Bricks (CSEB) in the province of North Kivu in the Democratic Republic of Congo (DRC). The study of the physical characteristics of lateritic soils was carried out. Samples were subjected to experimental identification tests on the physical characteristics (water content, density characteristics, particle size distribution and consistency). The results of the laboratory analysis of soil samples show that the water content varies between 5.4% and 36.99%. The density of the solid grains has an arithmetic mean of 2.5 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">. The apparent density varies from 0.83 to 1.35 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">. As for the dry density, it is in the range of 0.61 to 1.25 g/cm</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">. These relatively low densities indicate that the material studied ha</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">s</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> a significant degree of deformability. From the particle size analysis, it appears that the material studied contain</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">s</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> an important fraction of fine particles. According to the consistency study, the soils studied are plastic clay as Ap class according to the Central Laboratory for Roads and Bridges (CLRB) geotechnical classification system. The particle size curves of the studied samples are within the preferential range of good soils for the manufacture of CSEB. The points representing the studied samples are within the preferential plasticity range of good soils for the manufacture of CSEB. From the above parameters, it appears that the studied material is well adapted for the manufacture of the Compressed Stabilized Earth Bricks</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.
文摘The environmental effects of hydrokinetic turbines are still under investigation,reflecting the emerging status of this technology.This study investigates the interaction between hydrokinetic rotor wakes and fish swimming,revealing insights into fish biomechanics in complex flows and assessing the environ-mental implications of marine energy solutions.We conducted numerical simulations with the URANS approach and k−ω−SST turbulence closuremodeltopredictthree-dimensionalturbulent flowinthe OpenFOAM software.The hydrokinetic rotor wake was simulated employing the actuator line method,providing a computationally efficient alternative to full geometry simulations.For accurate replication of the motion of a fish-like tuna(Thunnus atlanticus),dynamic adaptive mesh discretization was employed.The results offer a comparative analysis of fish swimming performance within the wake rotor,particularly when immersed in the tip blade vortex,contrasted with scenarios where fish swim in undisturbed flow conditions.The analysis encompasses three-dimensional wake structures,force generation,efficiency,and equilibrium states(balancing drag and thrust)across varying Swimming numbers(Sw).Key findings in-clude the enhanced attachment of the leading-edge vortex due to the caudal fin’s interaction with the tip blade vortex,resulting in improved auto-propulsive force production;a reduced tail stride frequency observed in fish swimming downstream of the rotor to achieve longitudinal force balance compared to unperturbed flow;and transverse hydrodynamic forces pushing fish radially away from the wake’s influ-ence zone,potentially mitigating the risk of collision with turbine blades.
文摘In this article,a new method has been presented for the estimation of fracture toughness in brittle materials,which enjoys improved accuracy and reduced costs associated with fracture toughness testing procedure compared to similar previous methods,because a vast range of specimens with irregular cracks can be accommodated for testing.Micron-sized alumina powders containing 0.05 wt%magnesium oxide(MgO)nanoparticles were mixed and also together with 2.5 vol%,5 vol%,7.5 vol%,10 vol%,and 15 vol%of silicon carbide(SiC)nanopowders separately.By making and testing various types of ceramics with different mechanical properties,and considering the irregular cracks around the indented area caused by Vickers diamond indenter,a semi-empirical fracture toughness equation has been obtained.
基金supported by the National Natural Science Foundation of China(51773173,81973288)Hong Kong RGC(T12-201/20-R,12301720,12202422,RMGS 2020_4_01)+2 种基金HKBU SKLEBA SKL-CRF(SKLP_1718_P01)SZSTC(SGDX20190816230207535)the FET Open(Boheme)grant No.863179,and the Shanghai Pujiang Program 22PJ1406100.
文摘Developing versatile and robust surfaces that mimic the skins of living beings to regulate air/liquid/solid matter is critical for many bioinspired applications.Despite notable achievements,such as in the case of developing robust superhydrophobic surfaces,it remains elusive to realize simultaneously topology-specific superwettability and multipronged durability owing to their inherent tradeoff and the lack of a scalable fabrication method.Here,we present a largely unexplored strategy of preparing an all-perfluoropolymer(Teflon),nonlinear stability-assisted monolithic surface for efficient regulating matters.
文摘It is well known that the ambient temperature is a sensitive parameter which has a great effect on biology, technology, geology and even on human behavior. A prediction is a statement about an uncertain event. It is often, but not always, based upon experience or knowl- edge. Although guaranteed accurate information about the future is in many cases impossible, prediction can be useful to assist in making plans about possible developments. As a result, temperature profiles can be developed which accurately represent the expected ambient temperature exposure that this environment experiences during mea- surement. The ambient temperature over time is modeled based on the previous Train and Tmax data and using a Lagrange interpolation. To observe the comprehensive variation of ambient temperature the profile must be determined numerically. The model proposed in this paper can provide an acceptable way to measure the change in ambient temperature.
