The Tongon mine, the largest gold mine in C?te d’Ivoire, has been in operation since April 2010. However, to our knowledge to date, no study has been conducted on metallic contamination in suspended particulate matte...The Tongon mine, the largest gold mine in C?te d’Ivoire, has been in operation since April 2010. However, to our knowledge to date, no study has been conducted on metallic contamination in suspended particulate matter (PM<sub>10</sub> and PM<sub>2.5</sub>) where there is a lack of information on the carcinogenic and non-carcinogenic risk to human health associated with the exposure of populations in the Tongon area to these pollutants. The general objective of this study is to evaluate the level of contamination of PM<sub>10</sub>;PM<sub>2.5</sub> by heavy metals and their impact on the health of populations exposed to these pollutants in the Tongon gold mine area. The sampling and measurement of suspended particulate matter (PM<sub>10</sub> and PM<sub>2.5</sub>) were done using a MiniVol TAS passive air sampler. Heavy metal concentrations were determined by inductively coupled plasma mass spectroscopy (Nex ION 2000 ICP-MS, USA). The results indicate that the average concentrations of suspended particles (PM<sub>2.5</sub> and PM<sub>10</sub>) obtained are all above the recommended exposure limits. In addition, among the heavy metals contained in the suspended particles, the concentrations of arsenic and nickel are high and all above the standard limit values. The assessment of the health risks related to the inhalation of PM<sub>10</sub> particles reveals that their inhalation over a long period could cause a carcinogenic risk.展开更多
The present study focuses on the formulation of new composite consisting of plaster and raffia vinifera particle (RVP) with the purpose to reducing energy consumption. The aim of this study is to test this new compoun...The present study focuses on the formulation of new composite consisting of plaster and raffia vinifera particle (RVP) with the purpose to reducing energy consumption. The aim of this study is to test this new compound as an insulating eco-material in building in a tropical climate. The composites samples were developed by mixing plaster with raffia vinifera particles (RVP) using three different sizes (1.6 mm, 2.5 mm and 4 mm). The effects of four different RVP incorporations rates (i.e., 0wt%, 5wt%;10wt%;15wt%) on physical, thermal, mechanicals properties of the composites were investigated. In addition, the use of the raffia vinifera particles and plaster based composite material as building envelopes thermal insulation material is studied by the habitable cell thermal behavior instrumentation. The results indicate that the incorporation of raffia vinifera particle leads to improve the new composite physical, mechanical and thermal properties. And the parametric analysis reveals that the sampling rate and the size of raffia vinifera particles are the most decisive factor to impact these properties, and to decreases in the thermal conductivity which leads to an improvement to the thermal resistance and energy savings. The best improvement of plaster composite was obtained at the raffia vinifera particles size between 2.5 and 4.0 mm loading of 5wt% (C95P5R) with a good ratio of thermo-physical-mechanical properties. Additionally, the habitable cell experimental thermal behavior, with the new raffia vinifera particles and plaster-based composite as thermal insulating material for building walls, gives an average damping of 4°C and 5.8°C in the insulated house interior environment respectively for cold and hot cases compared to the outside environment and the uninsulated house interior environment. The current study highlights that this mixture gives the new composite thermal insulation properties applicable in the eco-construction of habitats in tropical environments.展开更多
A numerical approach to heat and mass transfer in a large water reservoir is presented. This water reservoir is likened to a parallelepiped reservoir whose vertical and lower walls are adiabatic and impermeable. The e...A numerical approach to heat and mass transfer in a large water reservoir is presented. This water reservoir is likened to a parallelepiped reservoir whose vertical and lower walls are adiabatic and impermeable. The equations that govern natural convection in water are solved by the finite volume method and Thomas’salgorithm. The adequacy between the velocity and pressure fields is ensured by the SIMPLE algorithm. We are going to evaluate the water losses by evaporation from three dams in the Nakanbé basin in Burkina Faso for a period of thirty years, that is to say from January 1, 1991, to March 15, 2020. The three dams have a rate of evaporation greater than 40% of the volume of water stored. Indeed the rate of evaporation in each dam increases with the water filling rate in the reservoir: we have observed the following results for each dam in the Nakanbé basin;for the date of 02/27/1988 to 03/13/2020., the Loumbila dam received a total volume of stored water of 22.02 Mm<sup>3</sup> and 10.57 Mm<sup>3</sup> as the total volume of water evaporated at the same date. At the Ouaga dam (2 + 3), it stored a water volume of 4.06 Mm<sup>3</sup> and evaporated 2.03 Mm<sup>3</sup> of its storage volume from 01/01/1988 to 05/07/2016. Finally, with regard to the Bagré dam, it stored 745.16 Mm<sup>3</sup> of water and 365.13 Mm<sup>3</sup> as the volume of water evaporated from 01/01/1993 to 03/31/2020.展开更多
This paper is related to study of the ion density recorded by the low altitude satellite DEMETER. It will present ionospheric perturbations observed during large seismic events.As the ionosphere is highly variable, th...This paper is related to study of the ion density recorded by the low altitude satellite DEMETER. It will present ionospheric perturbations observed during large seismic events.As the ionosphere is highly variable, the paper will show a statistical analysis performed on the plasma parameters during night time.An algorithm has been implemented to detect crests and troughs in the data before world-wide earthquakes.The earthquakes have been classified depending on their magnitude,depth,and location(land,below the sea,close to a coast). Due to the orbit,DEMETER returns above the same area every day(once during day time,once during night time) but not at the same distance of a given epicenter.Then,for each earthquake,data have been checked until 15 days before the shock when the distance between the trace of the orbit and the epicenter is less than 1 500 km.The results of the statistical analysis are presented as functions of various parameters.A comparison is done with two other databases where,on one hand,the location of the epicenters has been randomly modified, and on the other hand,the longitude of the epicenters has been shifted.Results show that the number and the intensity of the ionospheric perturbations are larger prior to earthquakes than prior to random events,and that the perturbations increase with the magnitude.展开更多
Observations of the Langmuir Probe Instrument(ISL,Instrument Sonde de Langmuir) onboard the DEMETER satellite during four years from 2006 to 2009 were used to analyze the tempo-spatial variations of electron density(N...Observations of the Langmuir Probe Instrument(ISL,Instrument Sonde de Langmuir) onboard the DEMETER satellite during four years from 2006 to 2009 were used to analyze the tempo-spatial variations of electron density(Ne) and temperature(Te) in the ionosphere.Twenty four research bins with each covering an area with 10° in longitude and 2° in latitude were selected to study the spatial distributions of Ne and Te.The results indicate that both Ne and Te have strong annual variations in the topside ionosphere at 660 km altitude.The semiannual anomaly and equinoctial asymmetry which are usually well known as the features of F-layer also exist in the topside ionosphere at low-and mid-latitudes.The yearly variation of Ne is opposite to the peak electron density of the F2-layer(NmF2) at higher latitudes in daytime and both are similar in nighttime.Also the yearly variations of Te at low-latitude are contrary to that at 600 km in daytime and similar in nighttime.An interesting feature of nighttime Te at low-latitude is an obvious annual variation in the northern hemisphere and semiannual variation in the southern hemisphere.The yearly variations of Te in daytime have negative and positive correlation with Ne at mid-and high-latitudes,respectively.Both Ne and Te in the neighborhood bins at the same latitude have a high correlation.In ionospheric events analyzing,this information may help to understand the characteristics of the variation and to distinguish the reliable abnormality from the normal background map.展开更多
This experimental study aims at the reuse of recycled aggregates (RA), resulting from the demolition of concrete, cement block and cement mortar, in the manufacture of common construction in Burkina Faso. The RA can r...This experimental study aims at the reuse of recycled aggregates (RA), resulting from the demolition of concrete, cement block and cement mortar, in the manufacture of common construction in Burkina Faso. The RA can readily replace natural aggregates in concrete. Then five formulations of natural and recycled aggregates based concrete for characteristic strength of 25 Mpa were prepared in addition to the natural aggregates base concrete named reference concrete (BN): two types of recycled aggregates concrete (BR), three types of recycles and natural combined aggregates base concrete (BC). The properties of natural and recycled aggregates were characterized and the physical, mechanical strength and durability properties were also evaluated for all concrete specimens. All the studied concrete formulation present a density between 2000 kg/m<sup>3</sup> ≤ ρ ≥ 2600 kg/m<sup>3</sup> and an average slump of 4.9 ± 0.1 cm. The obtained results indicate that the recycled aggregates are suitable for current concrete. Two out of the five combinations studied, such as the natural (BN) and combined aggregate (BC2) based concretes satisfy the mechanical characteristics (Rc<sub>28</sub> > 25 MPa) at 28 days of age and an average absorption coefficient of 2.93% and 3.98%. The recycled aggregate based concrete (BR1, BR2) and combined aggregate based concrete (BC1), gave respective average compressive strength of 21.55 MPa, 20.50 MPa and 20.30 MPa, i.e. a difference of 13.80% to 18.80% under the characteristic strength (25 MPa) aimed at 28 days of age. Thus, the recycled aggregates are in conformity with the normative prescriptions and their use for standard concrete gives adequate physical, mechanical and durability properties for the production of the C20/25 concrete series in the common civil engineering applications.展开更多
A sensor array comprising 9 potentiometric chemical sensors and some pattern recognition tools for the data processing has been applied in order to characterize the groundwater in the plain of Kairouan Region (Tunisia...A sensor array comprising 9 potentiometric chemical sensors and some pattern recognition tools for the data processing has been applied in order to characterize the groundwater in the plain of Kairouan Region (Tunisia). A total of 17 groundwater samples were collected from three different villages and analyzed for their chemical components. Nine chemical parameters were determined: Potassium, Sodium, Calcium, Ammonium, Cadmium, Chlorides, Nitrates, Fluoride and pH. Multi-sensor responses measured in each water sample were diagnosed by Principal Component Analysis (PCA) and Cluster Analysis (CA). PCA is a procedure for reducing data redundancy. CA is used to detect spatial similarity among sampling sites. This methodology is simple, rapid and the obtained results demonstrate that the electronic tongue technique based on the sensor array combined with pattern recognition method could be a useful tool for the characterization and the classification of wells water samples.展开更多
The hourly data of the vertical Z and the horizontal H components of 37 ground-based DC-ULF geomagnetic stations are examined during 20 April-12 May 2008. On 9 May 2008, three days before the Wenchuan MS 8.0 shock, an...The hourly data of the vertical Z and the horizontal H components of 37 ground-based DC-ULF geomagnetic stations are examined during 20 April-12 May 2008. On 9 May 2008, three days before the Wenchuan MS 8.0 shock, anomalies-a double low-point and a decreased amplitude-are registered on the curves of the Z component at 25 stations in a large-scale area surrounding the Wenchuan epicentral area. The H component shows none of the double low-point phenomenon but does exhibit a reduced magnitude at the same time. The geomagnetic index Kp is also examined and indicates that the anomalies appear at a solar quiet period. The appearing time shift(Tzs) between the first low-point on May 9 and the minimum point occurring time of May 1-5, 2008 is also checked.The results show that Tzs is on the order of 1-2 hours earlier or later than usual and there is a 2-6 hours’ gap between these two lowpoints. However, there is still a transition area which includes the epicenter where Tzs=0. Variation amplitude examined on vertical Z increases as the distance from the epicenter decreases. An Earth-air-ionosphere model has been employed to investigate a possible mechanism of this phenomenon and positive results have been unexpectedly attained. All these above-related results tend to prove that the variations of the Z and H on May 9, 2008 during the solar quiet period are probably associated with the forthcoming Wenchuan MS 8.0 earthquake.展开更多
We have theoretically resolved phonon excitations in quasi-two-dimensional organic crystals of polyacenic semiconductor material which may be obtained by the pyrolytic treatment of phenol-formaldehyde resin. A model f...We have theoretically resolved phonon excitations in quasi-two-dimensional organic crystals of polyacenic semiconductor material which may be obtained by the pyrolytic treatment of phenol-formaldehyde resin. A model for studying the dynamical properties using three polyacene chains is proposed with the aim to present the vibrational properties of this structure. It employs the formalism of solid states in two dimensions which admit phonons. A simulation process of the two-dimensional lattice structure shows that elastic waves may explain the existence of vibrational modes in the frequency range 100-400 cm-1. The presence of acoustic and optical like phonons is discussed in terms of the elastic force constants. A hyperfine resonance structure is obtained. It allows the analysis of the dynamical evolution in thin films of polyacene. It is found that the behavior of the phonon density of states exhibits resonance between modes in the structure.展开更多
Piezoelectricity is pivotal for applications in micro/nanoelectromechanical systems(MEMS/NEMS).Inducing such a property in 2D systems via the reduction of the dimensionality of their corresponding 3D bulk is here expl...Piezoelectricity is pivotal for applications in micro/nanoelectromechanical systems(MEMS/NEMS).Inducing such a property in 2D systems via the reduction of the dimensionality of their corresponding 3D bulk is here explored.Based on DFT theory and Gaussian-type-localized basis sets,the structural,electronic,mechanical,and piezoelectric properties of both 3D and 2D rare earth monochalcogenides RmX(Rm=Tm,Yb,Lu,and X=S,Se,Te)are investigated using the CRYSTAL code.Most intriguingly,the 2D LuX compounds display a buckled structure,where the Lu and X atoms protrude from the monolayer surface leading to an additional out-of-plane piezoelectric effect;(e_(31)=2104.84,1770.28,1689.79 pC/m,and d31=56.37,49.76,and 147.90 pm/V for LuS,LuSe,and LuTe,respectively).Such piezoelectric response is two orders of magnitude larger than the one of recently reported 2D ferroelectric MXenes,and is nearly thirty times larger than the commonly used AlN and GaN bulk structures.Furthermore,the reduced elastic constants obtained,when compared to other 2D materials,confirm the flexibility and softness of the considered 2D systems.展开更多
Wildfire events are increasing globally which may be partly associated with climate change,resulting in significant adverse impacts on local,regional air quality and global climate.In September 2020,a small wildfire(b...Wildfire events are increasing globally which may be partly associated with climate change,resulting in significant adverse impacts on local,regional air quality and global climate.In September 2020,a small wildfire(burned area:36.3 ha)event occurred in Souesmes(Loiret-Cher,Sologne,France),and its plume spread out over 200 km on the following day as observed by the MODIS satellite.Based on measurements at a suburban site(~50 km northwest of the fire location)in Orléans and backward trajectory analysis,young wildfire plumes were characterized.Significant increases in gaseous pollutants(CO,CH_(4),N_(2)O,VOCs,etc.)and particles(including black carbon)were found within the wildfire plumes,leading to a reduced air quality.Emission factors,defined as EF(X)=ΔX/ΔCO(where,X represents the target species),of various trace gases and black carbon within the young wildfire plumes were determined accordingly and compared with previous studies.Changes in the ambient ions(such as ammonium,sulfate,nitrate,chloride,and nitrite in the particle-and gasphase)and aerosol properties(e.g.,aerosol water content,aerosol p H)were also quantified and discussed.Moreover,we estimated the total carbon and climate-related species(e.g.,CO_(2),CH_(4),N_(2)O,and BC)emissions and compared them with fire emission inventories.Current biomass burning emission inventories have uncertainties in estimating small fire burned areas and emissions.For instance,we found that the Global Fire Assimilation System(GFAS)may underestimate emissions(e.g.,CO)of this small wildfire while other inventories(GFED and FINN)showed significant overestimation.Considering that it is the first time to record wildfire plumes in this region,related atmospheric implications are presented and discussed.展开更多
A tunable diode laser absorption spectrometer (TDLAS) for formaldehyde atmospheric measurements has been set up and validated through comparison experiments with a Fourier transform infrared spectrometer (FT-IR) in a ...A tunable diode laser absorption spectrometer (TDLAS) for formaldehyde atmospheric measurements has been set up and validated through comparison experiments with a Fourier transform infrared spectrometer (FT-IR) in a simulation chamber.Formaldehyde was generated in situ in the chamber from reaction of ethene with ozone.Three HCHO ro-vibrational line intensities (at 2909.71,2912.09 and 2914.46 cm-1) possibly used by TDLAS were calibrated by FT-IR spectra simultaneously recorded in the 1600-3200 cm-1 domain during ethene ozonolysis,enabling the on-line deduction of the varying concentration for HCHO in formation.The experimental line intensities values inferred confirmed the calculated ones from the updated HITRAN database.In addition,the feasibility of stratospheric in situ HCHO measurements using the 2912.09 cm-1 line was demonstrated.The TDLAS performances were also assessed,leading to a 2σ detection limit of 88 ppt in volume mixing ratio with a response time of 60 sec at 30 Torr and 294 K for 112 m optical path.As part of this work,the room-temperature rate constant of this reaction and the HCHO formation yield were found to be in excellent agreement with the compiled literature data.展开更多
The Giant Radio Array for Neutrino Detection(GRAND)is a planned large-scale observatory of ultra-high-energy(UHE)cosmic particles,with energies exceeding 10~8 Ge V.Its goal is to solve the long-standing mystery of the...The Giant Radio Array for Neutrino Detection(GRAND)is a planned large-scale observatory of ultra-high-energy(UHE)cosmic particles,with energies exceeding 10~8 Ge V.Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays.To do this,GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity.GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere.Its design is modular:20 separate,independent sub-arrays,each of 10000 radio antennas deployed over 10000 km^2.A staged construction plan will validate key detection techniques while achieving important science goals early.Here we present the science goals,detection strategy,preliminary design,performance goals,and construction plans for GRAND.展开更多
The organization of nano-objects on macroscopic surfaces is a key challenge for the technological improvement and implementation of nanotechnologies.For achieving operational functions,it is required to assemble nano-...The organization of nano-objects on macroscopic surfaces is a key challenge for the technological improvement and implementation of nanotechnologies.For achieving operational functions,it is required to assemble nano-objects as controllable building blocks in highly ordered superstructures.Herein,we demonstrate the growth and self-organization of metallic nanowires on surfaces into hexagonal superlattices with tunable characteristic lengths depending of the stabilizing surfactants employed.Starting from a reacting mixture containing a Pt(111)substrate,a Co organometallic precursor,an amine,and an acid dissolved in a solvent,we quantify the structural evolution of superlattices of vertical single-crystalline Co nanowires on Pt,using a combined analysis of small angle neutron scattering,transmission,and scanning electron microscopies.We show the concerted steps of a spontaneous growth and self-organization of the nanowires into two-dimensional(2D)hexagonal lattice on Pt,at intervals starting from a few hours of reaction to a highly ordered superlattice at longer times.Furthermore,it is shown that apart from long-chain acid and long-chain aliphatic amine pairs used as stabilizers,the combination of a long-chain aliphatic and a short-chain aromatic ligand in the synthesis can also be employed for the nanowire superlattices development.Interestingly,the possibility to employ different pairs allows quantitative modulation of the nanowire arrays,such as the interwire distance and the packing fraction.展开更多
Annual variations of interstellar scintillation can be modelled to constrain parameters of the ionized interstellar medium.If a pulsar is in a binary system,then investigating the orbital parameters is possible throug...Annual variations of interstellar scintillation can be modelled to constrain parameters of the ionized interstellar medium.If a pulsar is in a binary system,then investigating the orbital parameters is possible through analysis of the orbital variation of scintillation.In observations carried out from 2011 to 2020 by the European Pulsar Timing Array radio telescopes,PSRs J0613-0200and J0636+5128 show strong annual variations in their scintillation velocity,while the former additionally exhibits an orbital fluctuation.Bayesian theory and Markov-chain-Monte-Carlo methods are used to interpret these periodic variations.We assume a thin and anisotropic scattering screen model,and discuss the mildly and extremely anisotropic scattering cases.PSR J0613-0200is best described by mildly anisotropic scattering,while PSR J0636+5128 exhibits extremely anisotropic scattering.We measure the distance,velocity,and degree of anisotropy of the scattering screen for our two pulsars,finding that scattering screen distances from Earth for PSRs J0613-0200 and J0636+5128 are 316_(-20)^(+28)pc and 262_(-38)^(+96)pc,respectively.The positions of these scattering screens are coincident with the shell of the Local Bubble towards both pulsars.These associations add to the growing evidence of the Local Bubble shell as a dominant region of scattering along many sightlines.展开更多
文摘The Tongon mine, the largest gold mine in C?te d’Ivoire, has been in operation since April 2010. However, to our knowledge to date, no study has been conducted on metallic contamination in suspended particulate matter (PM<sub>10</sub> and PM<sub>2.5</sub>) where there is a lack of information on the carcinogenic and non-carcinogenic risk to human health associated with the exposure of populations in the Tongon area to these pollutants. The general objective of this study is to evaluate the level of contamination of PM<sub>10</sub>;PM<sub>2.5</sub> by heavy metals and their impact on the health of populations exposed to these pollutants in the Tongon gold mine area. The sampling and measurement of suspended particulate matter (PM<sub>10</sub> and PM<sub>2.5</sub>) were done using a MiniVol TAS passive air sampler. Heavy metal concentrations were determined by inductively coupled plasma mass spectroscopy (Nex ION 2000 ICP-MS, USA). The results indicate that the average concentrations of suspended particles (PM<sub>2.5</sub> and PM<sub>10</sub>) obtained are all above the recommended exposure limits. In addition, among the heavy metals contained in the suspended particles, the concentrations of arsenic and nickel are high and all above the standard limit values. The assessment of the health risks related to the inhalation of PM<sub>10</sub> particles reveals that their inhalation over a long period could cause a carcinogenic risk.
文摘The present study focuses on the formulation of new composite consisting of plaster and raffia vinifera particle (RVP) with the purpose to reducing energy consumption. The aim of this study is to test this new compound as an insulating eco-material in building in a tropical climate. The composites samples were developed by mixing plaster with raffia vinifera particles (RVP) using three different sizes (1.6 mm, 2.5 mm and 4 mm). The effects of four different RVP incorporations rates (i.e., 0wt%, 5wt%;10wt%;15wt%) on physical, thermal, mechanicals properties of the composites were investigated. In addition, the use of the raffia vinifera particles and plaster based composite material as building envelopes thermal insulation material is studied by the habitable cell thermal behavior instrumentation. The results indicate that the incorporation of raffia vinifera particle leads to improve the new composite physical, mechanical and thermal properties. And the parametric analysis reveals that the sampling rate and the size of raffia vinifera particles are the most decisive factor to impact these properties, and to decreases in the thermal conductivity which leads to an improvement to the thermal resistance and energy savings. The best improvement of plaster composite was obtained at the raffia vinifera particles size between 2.5 and 4.0 mm loading of 5wt% (C95P5R) with a good ratio of thermo-physical-mechanical properties. Additionally, the habitable cell experimental thermal behavior, with the new raffia vinifera particles and plaster-based composite as thermal insulating material for building walls, gives an average damping of 4°C and 5.8°C in the insulated house interior environment respectively for cold and hot cases compared to the outside environment and the uninsulated house interior environment. The current study highlights that this mixture gives the new composite thermal insulation properties applicable in the eco-construction of habitats in tropical environments.
文摘A numerical approach to heat and mass transfer in a large water reservoir is presented. This water reservoir is likened to a parallelepiped reservoir whose vertical and lower walls are adiabatic and impermeable. The equations that govern natural convection in water are solved by the finite volume method and Thomas’salgorithm. The adequacy between the velocity and pressure fields is ensured by the SIMPLE algorithm. We are going to evaluate the water losses by evaporation from three dams in the Nakanbé basin in Burkina Faso for a period of thirty years, that is to say from January 1, 1991, to March 15, 2020. The three dams have a rate of evaporation greater than 40% of the volume of water stored. Indeed the rate of evaporation in each dam increases with the water filling rate in the reservoir: we have observed the following results for each dam in the Nakanbé basin;for the date of 02/27/1988 to 03/13/2020., the Loumbila dam received a total volume of stored water of 22.02 Mm<sup>3</sup> and 10.57 Mm<sup>3</sup> as the total volume of water evaporated at the same date. At the Ouaga dam (2 + 3), it stored a water volume of 4.06 Mm<sup>3</sup> and evaporated 2.03 Mm<sup>3</sup> of its storage volume from 01/01/1988 to 05/07/2016. Finally, with regard to the Bagré dam, it stored 745.16 Mm<sup>3</sup> of water and 365.13 Mm<sup>3</sup> as the volume of water evaporated from 01/01/1993 to 03/31/2020.
基金supported by the Centre National d'Etudes Spatialesfunding from the European Community's Seventh Framework Programme(FP7/2007-2013)under grant agreement No.262005
文摘This paper is related to study of the ion density recorded by the low altitude satellite DEMETER. It will present ionospheric perturbations observed during large seismic events.As the ionosphere is highly variable, the paper will show a statistical analysis performed on the plasma parameters during night time.An algorithm has been implemented to detect crests and troughs in the data before world-wide earthquakes.The earthquakes have been classified depending on their magnitude,depth,and location(land,below the sea,close to a coast). Due to the orbit,DEMETER returns above the same area every day(once during day time,once during night time) but not at the same distance of a given epicenter.Then,for each earthquake,data have been checked until 15 days before the shock when the distance between the trace of the orbit and the epicenter is less than 1 500 km.The results of the statistical analysis are presented as functions of various parameters.A comparison is done with two other databases where,on one hand,the location of the epicenters has been randomly modified, and on the other hand,the longitude of the epicenters has been shifted.Results show that the number and the intensity of the ionospheric perturbations are larger prior to earthquakes than prior to random events,and that the perturbations increase with the magnitude.
基金supported by National Key Technology Research and Development Program (No 2008BAC35B02)
文摘Observations of the Langmuir Probe Instrument(ISL,Instrument Sonde de Langmuir) onboard the DEMETER satellite during four years from 2006 to 2009 were used to analyze the tempo-spatial variations of electron density(Ne) and temperature(Te) in the ionosphere.Twenty four research bins with each covering an area with 10° in longitude and 2° in latitude were selected to study the spatial distributions of Ne and Te.The results indicate that both Ne and Te have strong annual variations in the topside ionosphere at 660 km altitude.The semiannual anomaly and equinoctial asymmetry which are usually well known as the features of F-layer also exist in the topside ionosphere at low-and mid-latitudes.The yearly variation of Ne is opposite to the peak electron density of the F2-layer(NmF2) at higher latitudes in daytime and both are similar in nighttime.Also the yearly variations of Te at low-latitude are contrary to that at 600 km in daytime and similar in nighttime.An interesting feature of nighttime Te at low-latitude is an obvious annual variation in the northern hemisphere and semiannual variation in the southern hemisphere.The yearly variations of Te in daytime have negative and positive correlation with Ne at mid-and high-latitudes,respectively.Both Ne and Te in the neighborhood bins at the same latitude have a high correlation.In ionospheric events analyzing,this information may help to understand the characteristics of the variation and to distinguish the reliable abnormality from the normal background map.
文摘This experimental study aims at the reuse of recycled aggregates (RA), resulting from the demolition of concrete, cement block and cement mortar, in the manufacture of common construction in Burkina Faso. The RA can readily replace natural aggregates in concrete. Then five formulations of natural and recycled aggregates based concrete for characteristic strength of 25 Mpa were prepared in addition to the natural aggregates base concrete named reference concrete (BN): two types of recycled aggregates concrete (BR), three types of recycles and natural combined aggregates base concrete (BC). The properties of natural and recycled aggregates were characterized and the physical, mechanical strength and durability properties were also evaluated for all concrete specimens. All the studied concrete formulation present a density between 2000 kg/m<sup>3</sup> ≤ ρ ≥ 2600 kg/m<sup>3</sup> and an average slump of 4.9 ± 0.1 cm. The obtained results indicate that the recycled aggregates are suitable for current concrete. Two out of the five combinations studied, such as the natural (BN) and combined aggregate (BC2) based concretes satisfy the mechanical characteristics (Rc<sub>28</sub> > 25 MPa) at 28 days of age and an average absorption coefficient of 2.93% and 3.98%. The recycled aggregate based concrete (BR1, BR2) and combined aggregate based concrete (BC1), gave respective average compressive strength of 21.55 MPa, 20.50 MPa and 20.30 MPa, i.e. a difference of 13.80% to 18.80% under the characteristic strength (25 MPa) aimed at 28 days of age. Thus, the recycled aggregates are in conformity with the normative prescriptions and their use for standard concrete gives adequate physical, mechanical and durability properties for the production of the C20/25 concrete series in the common civil engineering applications.
文摘A sensor array comprising 9 potentiometric chemical sensors and some pattern recognition tools for the data processing has been applied in order to characterize the groundwater in the plain of Kairouan Region (Tunisia). A total of 17 groundwater samples were collected from three different villages and analyzed for their chemical components. Nine chemical parameters were determined: Potassium, Sodium, Calcium, Ammonium, Cadmium, Chlorides, Nitrates, Fluoride and pH. Multi-sensor responses measured in each water sample were diagnosed by Principal Component Analysis (PCA) and Cluster Analysis (CA). PCA is a procedure for reducing data redundancy. CA is used to detect spatial similarity among sampling sites. This methodology is simple, rapid and the obtained results demonstrate that the electronic tongue technique based on the sensor array combined with pattern recognition method could be a useful tool for the characterization and the classification of wells water samples.
基金supported by NSFC (National Natural Science Foundation of China) under grant agreement No.41774084National Key R & D Program of China under grant No.2018YFC 1503506
文摘The hourly data of the vertical Z and the horizontal H components of 37 ground-based DC-ULF geomagnetic stations are examined during 20 April-12 May 2008. On 9 May 2008, three days before the Wenchuan MS 8.0 shock, anomalies-a double low-point and a decreased amplitude-are registered on the curves of the Z component at 25 stations in a large-scale area surrounding the Wenchuan epicentral area. The H component shows none of the double low-point phenomenon but does exhibit a reduced magnitude at the same time. The geomagnetic index Kp is also examined and indicates that the anomalies appear at a solar quiet period. The appearing time shift(Tzs) between the first low-point on May 9 and the minimum point occurring time of May 1-5, 2008 is also checked.The results show that Tzs is on the order of 1-2 hours earlier or later than usual and there is a 2-6 hours’ gap between these two lowpoints. However, there is still a transition area which includes the epicenter where Tzs=0. Variation amplitude examined on vertical Z increases as the distance from the epicenter decreases. An Earth-air-ionosphere model has been employed to investigate a possible mechanism of this phenomenon and positive results have been unexpectedly attained. All these above-related results tend to prove that the variations of the Z and H on May 9, 2008 during the solar quiet period are probably associated with the forthcoming Wenchuan MS 8.0 earthquake.
文摘We have theoretically resolved phonon excitations in quasi-two-dimensional organic crystals of polyacenic semiconductor material which may be obtained by the pyrolytic treatment of phenol-formaldehyde resin. A model for studying the dynamical properties using three polyacene chains is proposed with the aim to present the vibrational properties of this structure. It employs the formalism of solid states in two dimensions which admit phonons. A simulation process of the two-dimensional lattice structure shows that elastic waves may explain the existence of vibrational modes in the frequency range 100-400 cm-1. The presence of acoustic and optical like phonons is discussed in terms of the elastic force constants. A hyperfine resonance structure is obtained. It allows the analysis of the dynamical evolution in thin films of polyacene. It is found that the behavior of the phonon density of states exhibits resonance between modes in the structure.
文摘Piezoelectricity is pivotal for applications in micro/nanoelectromechanical systems(MEMS/NEMS).Inducing such a property in 2D systems via the reduction of the dimensionality of their corresponding 3D bulk is here explored.Based on DFT theory and Gaussian-type-localized basis sets,the structural,electronic,mechanical,and piezoelectric properties of both 3D and 2D rare earth monochalcogenides RmX(Rm=Tm,Yb,Lu,and X=S,Se,Te)are investigated using the CRYSTAL code.Most intriguingly,the 2D LuX compounds display a buckled structure,where the Lu and X atoms protrude from the monolayer surface leading to an additional out-of-plane piezoelectric effect;(e_(31)=2104.84,1770.28,1689.79 pC/m,and d31=56.37,49.76,and 147.90 pm/V for LuS,LuSe,and LuTe,respectively).Such piezoelectric response is two orders of magnitude larger than the one of recently reported 2D ferroelectric MXenes,and is nearly thirty times larger than the commonly used AlN and GaN bulk structures.Furthermore,the reduced elastic constants obtained,when compared to other 2D materials,confirm the flexibility and softness of the considered 2D systems.
基金supported by the VOLTAIRE project (ANR-10-LABX-100-01)funded by the ANR and the PIVOTS project provided by the Region Centre−Val de Loire (ARD 2020 program and CPER 2015−2020).
文摘Wildfire events are increasing globally which may be partly associated with climate change,resulting in significant adverse impacts on local,regional air quality and global climate.In September 2020,a small wildfire(burned area:36.3 ha)event occurred in Souesmes(Loiret-Cher,Sologne,France),and its plume spread out over 200 km on the following day as observed by the MODIS satellite.Based on measurements at a suburban site(~50 km northwest of the fire location)in Orléans and backward trajectory analysis,young wildfire plumes were characterized.Significant increases in gaseous pollutants(CO,CH_(4),N_(2)O,VOCs,etc.)and particles(including black carbon)were found within the wildfire plumes,leading to a reduced air quality.Emission factors,defined as EF(X)=ΔX/ΔCO(where,X represents the target species),of various trace gases and black carbon within the young wildfire plumes were determined accordingly and compared with previous studies.Changes in the ambient ions(such as ammonium,sulfate,nitrate,chloride,and nitrite in the particle-and gasphase)and aerosol properties(e.g.,aerosol water content,aerosol p H)were also quantified and discussed.Moreover,we estimated the total carbon and climate-related species(e.g.,CO_(2),CH_(4),N_(2)O,and BC)emissions and compared them with fire emission inventories.Current biomass burning emission inventories have uncertainties in estimating small fire burned areas and emissions.For instance,we found that the Global Fire Assimilation System(GFAS)may underestimate emissions(e.g.,CO)of this small wildfire while other inventories(GFED and FINN)showed significant overestimation.Considering that it is the first time to record wildfire plumes in this region,related atmospheric implications are presented and discussed.
基金supported by the European Commission through the 7th Framework Programme under the grant agreement #228335 (EUROCHAMP-2 Project)by the French CNRS-INSU Programme National de Chimie Atmosphrique
文摘A tunable diode laser absorption spectrometer (TDLAS) for formaldehyde atmospheric measurements has been set up and validated through comparison experiments with a Fourier transform infrared spectrometer (FT-IR) in a simulation chamber.Formaldehyde was generated in situ in the chamber from reaction of ethene with ozone.Three HCHO ro-vibrational line intensities (at 2909.71,2912.09 and 2914.46 cm-1) possibly used by TDLAS were calibrated by FT-IR spectra simultaneously recorded in the 1600-3200 cm-1 domain during ethene ozonolysis,enabling the on-line deduction of the varying concentration for HCHO in formation.The experimental line intensities values inferred confirmed the calculated ones from the updated HITRAN database.In addition,the feasibility of stratospheric in situ HCHO measurements using the 2912.09 cm-1 line was demonstrated.The TDLAS performances were also assessed,leading to a 2σ detection limit of 88 ppt in volume mixing ratio with a response time of 60 sec at 30 Torr and 294 K for 112 m optical path.As part of this work,the room-temperature rate constant of this reaction and the HCHO formation yield were found to be in excellent agreement with the compiled literature data.
基金The GRAND project is supported by the APACHE of the French Agence Nationale de la Recherche(Grant No.ANR-16-CE31-0001)the FranceChina Particle Physics Laboratory,the China Exchange Program from the Royal Netherlands Academy of Arts and Sciences and the Chinese Academy of Sciences+15 种基金the Key Projects of Frontier Science of the Chinese Academy of Sciences(Grant No.QYZDY-SSW-SLH022)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB23000000)the National Key R&D Program of China(Grant No.2018YFA0404601)supported by Sao Paulo Research Foundation(FAPESP)(Grant No.2017/12828-4)partially supported from National Science Foundation(Grant Nos.PHY-1404311,and PHY-1714479)supported by Danish National Research Foundation(DNRF91)Danmarks Grundforskningsfond(Grant No.1041811001)Villum Fonden(Grant No.13164)Washington Carvalho Jr.is supported by Sao Paulo Research Foundation(FAPESP)(Grant No.2015/15735-1)supported by the National Natural Science Foundation of China(Grant No.11375209)supported by the Flemish Foundation for Scientific Research(Grant No.FWO-12L3715N–K.D.de Vries)supported by the Netherlands Organisation for Scientific Research(NWO)supported by the Key Projects of Frontier Science of Chinese Academy of Sciences,(Grant No.QYZDY-SSWSLH022)the Strategic Priority Research Program of Chinese Academy of Sciences,(Grant No.XDB23000000)supported by the National Natural Science Foundation of China(Grant No.11505213)“Data analysis for radio detection array at 21CMA base”
文摘The Giant Radio Array for Neutrino Detection(GRAND)is a planned large-scale observatory of ultra-high-energy(UHE)cosmic particles,with energies exceeding 10~8 Ge V.Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays.To do this,GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity.GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere.Its design is modular:20 separate,independent sub-arrays,each of 10000 radio antennas deployed over 10000 km^2.A staged construction plan will validate key detection techniques while achieving important science goals early.Here we present the science goals,detection strategy,preliminary design,performance goals,and construction plans for GRAND.
基金This work was supported by the Agence Nationale de la Recherche(France)under contract No.ANR-14-CE07-0025-01(DENSAR)。
文摘The organization of nano-objects on macroscopic surfaces is a key challenge for the technological improvement and implementation of nanotechnologies.For achieving operational functions,it is required to assemble nano-objects as controllable building blocks in highly ordered superstructures.Herein,we demonstrate the growth and self-organization of metallic nanowires on surfaces into hexagonal superlattices with tunable characteristic lengths depending of the stabilizing surfactants employed.Starting from a reacting mixture containing a Pt(111)substrate,a Co organometallic precursor,an amine,and an acid dissolved in a solvent,we quantify the structural evolution of superlattices of vertical single-crystalline Co nanowires on Pt,using a combined analysis of small angle neutron scattering,transmission,and scanning electron microscopies.We show the concerted steps of a spontaneous growth and self-organization of the nanowires into two-dimensional(2D)hexagonal lattice on Pt,at intervals starting from a few hours of reaction to a highly ordered superlattice at longer times.Furthermore,it is shown that apart from long-chain acid and long-chain aliphatic amine pairs used as stabilizers,the combination of a long-chain aliphatic and a short-chain aromatic ligand in the synthesis can also be employed for the nanowire superlattices development.Interestingly,the possibility to employ different pairs allows quantitative modulation of the nanowire arrays,such as the interwire distance and the packing fraction.
基金supported by the National Natural Science Foundation of China(Grant No.12003047)the Major Science and Technology Program of Xinjiang Uygur Autonomous Region(Grant No.2022A03013-2)+2 种基金the Natural Science Foundation of Xinjiang Uygur Autonomous Region(Grant No.2022D01D85)support by the Deutsche Forschungsgemeinschaft(DFG)through the Heisenberg programme(Project No.433075039)financial support from“Programme National de Cosmologie et Galaxies”(PNCG)of CNRS/INSU,France。
文摘Annual variations of interstellar scintillation can be modelled to constrain parameters of the ionized interstellar medium.If a pulsar is in a binary system,then investigating the orbital parameters is possible through analysis of the orbital variation of scintillation.In observations carried out from 2011 to 2020 by the European Pulsar Timing Array radio telescopes,PSRs J0613-0200and J0636+5128 show strong annual variations in their scintillation velocity,while the former additionally exhibits an orbital fluctuation.Bayesian theory and Markov-chain-Monte-Carlo methods are used to interpret these periodic variations.We assume a thin and anisotropic scattering screen model,and discuss the mildly and extremely anisotropic scattering cases.PSR J0613-0200is best described by mildly anisotropic scattering,while PSR J0636+5128 exhibits extremely anisotropic scattering.We measure the distance,velocity,and degree of anisotropy of the scattering screen for our two pulsars,finding that scattering screen distances from Earth for PSRs J0613-0200 and J0636+5128 are 316_(-20)^(+28)pc and 262_(-38)^(+96)pc,respectively.The positions of these scattering screens are coincident with the shell of the Local Bubble towards both pulsars.These associations add to the growing evidence of the Local Bubble shell as a dominant region of scattering along many sightlines.
