We investigate the spatial and temporal correlations of hot-electron generation in high-intensity laser interaction with massive and thin copper targets under conditions relevant to inertial confinement fusion.Using K...We investigate the spatial and temporal correlations of hot-electron generation in high-intensity laser interaction with massive and thin copper targets under conditions relevant to inertial confinement fusion.Using Ka time-resolved imaging,it is found that in the case of massive targets,the hot-electron generation follows the laser pulse intensity with a short delay needed for favorable plasma formation.Conversely,a significant delay in the x-ray emission compared with the laser pulse intensity profile is observed in the case of thin targets.Theoretical analysis and numerical simulations suggest that this is related to radiation preheating of the foil and the increase in hot-electron lifetime in a hot expanding plasma.展开更多
Nd-Fe-B permanent magnets play a crucial role in energy conversion and electronic devices.The essential magnetic properties of Nd-Fe-B magnets,particularly coercivity and remanent magnetization,are significantly infue...Nd-Fe-B permanent magnets play a crucial role in energy conversion and electronic devices.The essential magnetic properties of Nd-Fe-B magnets,particularly coercivity and remanent magnetization,are significantly infuenced by the phase characteristics and microstructure.In this work,Nd-Fe-B magnets were manufactured using vacuum induction melting(VIM),laser directed energy deposition(LDED)and laser powder bed fusion(LPBF)technologies.Themicrostructure evolution and phase selection of Nd-Fe-B magnets were then clarified in detail.The results indicated that the solidification velocity(V)and cooling rate(R)are key factors in the phase selection.In terms of the VIM-casting Nd-Fe-B magnet,a large volume fraction of theα-Fe soft magnetic phase(39.7 vol.%)and Nd2Fe17Bxmetastable phase(34.7 vol.%)areformed due to the low R(2.3×10-1?C s-1),whereas only a minor fraction of the Nd2Fe14B hard magnetic phase(5.15 vol.%)is presented.For the LDED-processed Nd-Fe-B deposit,although the Nd2Fe14B hard magnetic phase also had a low value(3.4 vol.%)as the values of V(<10-2m s-1)and R(5.06×103?C s-1)increased,part of theα-Fe soft magnetic phase(31.7vol.%)is suppressed,and a higher volume of Nd2Fe17Bxmetastable phases(47.5 vol.%)areformed.As a result,both the VIM-casting and LDED-processed Nd-Fe-B deposits exhibited poor magnetic properties.In contrast,employing the high values of V(>10-2m s-1)and R(1.45×106?C s-1)in the LPBF process resulted in the substantial formation of the Nd2Fe14B hard magnetic phase(55.8 vol.%)directly from the liquid,while theα-Fe soft magnetic phase and Nd2Fe17Bxmetastable phase precipitation are suppressed in the LPBF-processed Nd-Fe-B magnet.Additionally,crystallographic texture analysis reveals that the LPBF-processedNd-Fe-B magnets exhibit isotropic magnetic characteristics.Consequently,the LPBF-processed Nd-Fe-B deposit,exhibiting a coercivity of 656 k A m-1,remanence of 0.79 T and maximum energy product of 71.5 k J m-3,achieved an acceptable magnetic performance,comparable to other additive manufacturing processed Nd-Fe-B magnets from MQP(Nd-lean)Nd-Fe-Bpowder.展开更多
Background: The investigation of toxin genes in strains involved in staphylococcal food poisoning contributes to food safety. The aim of this study was to isolate and identify enterotoxigenic Staphylococcus strains fr...Background: The investigation of toxin genes in strains involved in staphylococcal food poisoning contributes to food safety. The aim of this study was to isolate and identify enterotoxigenic Staphylococcus strains from dried, smoked, and braised fish sold in Ouagadougou markets. Methodology: Staphylococci were isolated using standard microbiology methods. Staphylococcus strains were identified using API Staph kit (Reference # 20500, BioMerieux S.A., Marcy l'Etoile, France). The molecular identification of isolated Staphylococcus aureus strains was specifically confirmed by PCR using the Staur4 and Staur6 primers. The genes encoding enterotoxins, enterotoxin-like toxins, exfoliative toxins, and TSST-1 toxin were detected by multiplex PCR using specific primers from Inquaba Biotec West Africa Ltd, Africa's Genomics Company. Results: The results of the microbiological quality assessment indicated that most of the samples analyzed were found to be of unsatisfactory microbiological quality according to the Staphylococcus aureus microbiological criteria (m = 102). Overall, only 12.55% of samples were satisfactory, while 97.45% were unsatisfactory. The STAPH API gallery allowed the identification of the following species: Staphylococcus aureus, Staphylococcus xylosus, Staphylococcus lugdunensis, Staphylococcus hominis, Staphylococcus haemolyticus, Staphylococcus lentus, Staphylococcus sciuri and Staphylococcus capitis. Of the 108 Staphylococcus isolates, 81 (75%) showed at least one (1) toxin gene. Among the 21 toxin genes tested in this study, 20 genes were detected in all strains analyzed. The staphylococcal toxin genes detected were present in both Staphylococcus aureus and the other coagulase-negative strains isolated in this study. In addition, these genes are found individually or in association in certain strains. The most frequent genes detected in toxin gene-positive strains were: the tsst-1 gene in 45 isolated strains (41.7%), sei (16/14.8%), seg (13/12%), ser (7/6.5%) sec (6/5.5%), and sea (5/4.6%) for staphylococcal enterotoxins, seln (14/12.9%), selq (8/7.4%), for enterotoxin-like toxin gene and eta (3/2.7%) for exfoliative toxin genes. Conclusion: This study highlighted the pathogenicity of Staphylococcus strains isolated from dried, smoked, and braised fish sold in Ouagadougou markets. Monitoring toxin-producing strains of Staphylococcus is invaluable for better prevention of food poisoning.展开更多
Electrocatalytic water splitting is crucial for H2generation via hydrogen evolution reaction(HER)but subject to the sluggish dynamics of oxygen evolution reaction(OER).In this work,single Fe atomdoped MoS_(2)nanosheet...Electrocatalytic water splitting is crucial for H2generation via hydrogen evolution reaction(HER)but subject to the sluggish dynamics of oxygen evolution reaction(OER).In this work,single Fe atomdoped MoS_(2)nanosheets(SFe-DMNs)were prepared based on the high-throughput density functional theory(DFT)calculation screening.Due to the synergistic effect between Fe atom and MoS_(2)and optimized intermediate binding energy,the SFe-DMNs could deliver outstanding activity for both HER and OER.When assembled into a two-electrode electrolytic cell,the SFe-DMNs could achieve the current density of 50 mA cm^(-2)at a low cell voltage of 1.55 V under neutral condition.These results not only confirmed the effectiveness of high-throughput screening,but also revealed the excellent activity and thus the potential applications in fuel cells of SFe-DMNs.展开更多
This study presents a contribution to the development of a model for vegetable oil droplets vaporization, with a particular focus on the influence of the experimental set-up for their use as fuel in diesel engines. Tw...This study presents a contribution to the development of a model for vegetable oil droplets vaporization, with a particular focus on the influence of the experimental set-up for their use as fuel in diesel engines. Two systems were considered: an open-environment system obtained through a hot gas flow, and a closed-environment system. Vaporization was conducted under identical conditions, with the results subsequently compared. The findings indicate that, for temperatures between 473 K and 673 K, droplets behaviour in both systems presents only a heating and expansion phase. For temperatures above 673 K, the behaviour of the droplets differs between the devices. In the open environment device, a linear reduction in droplets diameter is observed following the transient phase, suggesting stationary vaporization and enabling the calculation of a vaporization constant and the well-known D2 law is respected. In the closed-environment device, puffing, micro-explosions and gas ejections are observed, and it is not possible to determine vaporization constant and D2 law is not respected. The results demonstrate the necessity of developing a model for the thermal decomposition of vegetable oil before attempting to create a model for the vaporization of these oils. In order to achieve this, it is essential to construct an experimental setup that more closely emulates the real conditions within the combustion chamber of a diesel engine, taking into account the variables of pressure, temperature and the heating process.展开更多
Magnetic reconnection and dipolarization are crucial processes driving magnetospheric dynamics,including particle energization,mass circulation,and auroral processes,among others.Recent studies have revealed that thes...Magnetic reconnection and dipolarization are crucial processes driving magnetospheric dynamics,including particle energization,mass circulation,and auroral processes,among others.Recent studies have revealed that these processes at Saturn and Jupiter are fundamentally different from the ones at Earth.The reconnection and dipolarization processes are far more important than previously expected in the dayside magnetodisc of Saturn and potentially Jupiter.Dayside magnetodisc reconnection was directly identified by using Cassini measurements(Guo RL et al.,2018b)and was found to be drizzle-like and rotating in the magnetosphere of Saturn(Delamere et al.,2015b;Yao ZH et al.,2017a;Guo RL et al.,2019).Moreover,magnetic dipolarization could also exist at Saturn’s dayside(Yao ZH et al.,2018),which is fundamentally different from the terrestrial situation.These new results significantly improve our understanding of giant planetary magnetospheric dynamics and provide key insights revealing the physics of planetary aurorae.Here,we briefly review these recent advances and their potential implications for future investigations.展开更多
This study proposes an advanced leaching method using organic acids to recover rare earth elements(REEs)from NdFeB permanent magnets from end-of-life computers hard disk drives(HDDs).The end-oflife HDDs were first dis...This study proposes an advanced leaching method using organic acids to recover rare earth elements(REEs)from NdFeB permanent magnets from end-of-life computers hard disk drives(HDDs).The end-oflife HDDs were first dismantled in order to recover NdFeB magnets,which were then thermally demagnetized at 350℃during 30 min before crushing in a ball mill under inert atmosphere.Scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS)analyses performed on the NdFeB magnets show the heterogeneous structure containing the major matric phase Nd_(2)Fe_(14)B and the REEsrich phase containing Nd and Pr oxides.Additionally,X-ray diffraction(XRD)and Mossbauer spectroscopy(MS)analyses on the ground NdFeB magnet show that grinding NdFeB magnets under inert atmosphere helps to minimize its oxidation.Chemical analysis shows that the composition of the ground sample is Nd:22.8 wt%,Pr:3.3 wt%,Dy:1.2 wt%,Fe:62.6 wt%,Co:1.5 wt%,B:0.9 wt%,Ni:0.6 wt%.Diagrams of speciation and equilibrium phases(E_(h) vs.pH)were calculated to determine the predominance of the formed species in the REEs-organic acids systems.The influence of the organic acid type(acetic acid,formic acid,citric acid and tartaric acid),the acid concentration(10 vol%,up to saturation),and the solid/liquid(S/L)ratio(0.5%-10%)on NdFeB magnets leaching was investigated employing an optimal experimental design conceived by the statistical software JMP.Acetic acid(CH_(3)COOH)shows the highest leaching performance of REEs,allowing leaching yields over 90%for Nd,Dy and Pr in the acid concentration range of 1.6-10 mol/L and the S/L ratio range of 0.5%-5%at a temperature of 60℃.The results presented in this investigation suggest that REEs can be recovered from magnets of end-of-life HDDs using an eco-friendly method assisted by organic acids.展开更多
Hydrogen absorption and desorption characteristics for high coercivity NdDyFeCoNbCuB sintered bulk magnets were studied, by differential scanning calorimetry （DSC） measurement and hydrogenation kinetics measurement....Hydrogen absorption and desorption characteristics for high coercivity NdDyFeCoNbCuB sintered bulk magnets were studied, by differential scanning calorimetry （DSC） measurement and hydrogenation kinetics measurement. The DSC measurements showed that hydrogenation of Nd-rich phase occurred in the temperature range of 40-185 ℃, hydrogenation of the tetragonal （Ф） phase in the temperature range of 185-220 ℃, as well as the disproportionation of the Ф phase that occurred in a broad temperature range from around 500 to 800 ℃. The hydrogenation kinetics measurements indicated that hydrogen absorption of the bulk magnets at 50 ℃ absorbed more hydrogen than at 150 ℃, although this procedure was slower at 50 ℃ than at 150℃. This phenomenon was discussed by means of pressure-concentration-temperature （p-c-T） diagrams.展开更多
Deadlock resolution strategies based on siphon control are widely investigated.Their computational efficiency largely depends on siphon computation.Mixed-integer programming(MIP)can be utilized for the computation of ...Deadlock resolution strategies based on siphon control are widely investigated.Their computational efficiency largely depends on siphon computation.Mixed-integer programming(MIP)can be utilized for the computation of an emptiable siphon in a Petri net(PN).Based on it,deadlock resolution strategies can be designed without requiring complete siphon enumeration that has exponential complexity.Due to this reason,various MIP methods are proposed for various subclasses of PNs.This work proposes an innovative MIP method to compute an emptiable minimal siphon(EMS)for a subclass of PNs named S^(4)PR.In particular,many particular structural characteristics of EMS in S4 PR are formalized as constraints,which greatly reduces the solution space.Experimental results show that the proposed MIP method has higher computational efficiency.Furthermore,the proposed method allows one to determine the liveness of an ordinary S^(4)PR.展开更多
This review summarizes the recent advances on the application of ^(57)Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine st...This review summarizes the recent advances on the application of ^(57)Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine structures of the Ce_(2)Fe_(14)B,(Ce,Nd)_(2)Fe_(14)B and MM_(2)Fe_(14)B phases are well-defined by using the model based on the Wigner-Seitz analysis of the crystal structure. The results show that the isomer shift δ and the quadrupole splitting öEQ of those 2:14:1 phases show minor changes with the Nd content, while the hyperfine field Bhfincreases monotonically with increasing Nd content and its value is influenced by the element segregation and phase separation in the 2:14:1 phase. Then, the hyperfine structures of the low fraction secondary phases are determined by the ^(57)Fe Mössbauer spectrometry due to its high sensitivity. On this basis,the content, magnetic behavior, and magnetization of the REFe_(2) phase, the amorphous grain boundary(GB) phase, and the amorphous worm-like phase, as well as their effects on the magnetic properties, are systematically studied.展开更多
A novel statistical approach to evaluate the manufacturing quality of press coated tablets in terms of the centering of their core is presented. We also provide a formula to determine the necessary sample size. This a...A novel statistical approach to evaluate the manufacturing quality of press coated tablets in terms of the centering of their core is presented. We also provide a formula to determine the necessary sample size. This approach is applied to real data.展开更多
We introduce a new approach to image super-resolution. The idea is to use a simple wavelet-based linear interpolation scheme as our initial estimate of high-resolution image;and to intensify geometric structure in ini...We introduce a new approach to image super-resolution. The idea is to use a simple wavelet-based linear interpolation scheme as our initial estimate of high-resolution image;and to intensify geometric structure in initial estimation with an iterative projection process based on hard-thresholding scheme in a new angular multiselectivity domain. This new domain is defined by combining of laplacian pyramid and angular multiselectivity decomposition, the result is multiselective contourlets which can capture and restore adaptively and slightly better geometric structure of image. The experimental results demonstrate the effectiveness of the proposed approach.展开更多
Mobile games are gaining in popularity among students, although the factors driving engagement remain poorly understood. This study, conducted among 378 students studying for a Bachelor’s degree in Computer and Digit...Mobile games are gaining in popularity among students, although the factors driving engagement remain poorly understood. This study, conducted among 378 students studying for a Bachelor’s degree in Computer and Digital Sciences at the Université Virtuelle de Côte d’Ivoire, explores the influence of game assets and colours on player engagement. Using an online questionnaire, the study identified students’ gaming preferences and their perception of colours. The results show that the key elements most favoured by students are graphics, sound design, the game system, narrative, interactivity and accessibility. What’s more, colour plays a decisive role in their preferences and commitment to educational mobile games.展开更多
Mixed convection of heat and mass transfer in an isosceles trapezoidal cavity has been studied numerically. Constant heat flux is imposed through four outlets and the grid is insulated. The inclined walls are maintain...Mixed convection of heat and mass transfer in an isosceles trapezoidal cavity has been studied numerically. Constant heat flux is imposed through four outlets and the grid is insulated. The inclined walls are maintained in natural convection while the lower horizontal wall is adiabatic. These conditions reflect the air draft zone of the ASUTO charcoal stove. The governing two-di- mensional flow equations have been solved by using the finite difference method and Thomas’s algorithm. The investigations are conducted for different values of Richardson (R<sub>i</sub>), Reynolds number (R<sub>e</sub>) and inclination angles of sidewalls. The results are presented in terms of streamlines, isotherms, moisture contours. It was found that for Reynolds number (R<sub>e</sub>) equal to 100, the flow pattern is strongly dependent on the inclination angle and Richardson number. Thus, for high Richardson number (R<sub>i</sub>) values (10, 100), the dominance of natural convection over the flow structure decreases with the decreasing of the inclination angle of sidewalls of the cavity. For R<sub>i</sub> = 1, an optimum air draft corresponds to an inclination angle in the vicinity of 22° while for R<sub>i</sub> = 10 or 100 (in dominance of natural convection), the optimum inclination angle for air draft is in the vicinity of 15°.展开更多
Hepatic fibrosis is a pathological lesion, characterized by the progressive accumulation of extracellularmatrix （ECM） in the perisinusoidal space and it is a major problem in chronic liver diseases. Phenotypicactiva...Hepatic fibrosis is a pathological lesion, characterized by the progressive accumulation of extracellularmatrix （ECM） in the perisinusoidal space and it is a major problem in chronic liver diseases. Phenotypicactivation of hepatic stellate cells （HSC） plays a central role in the progression of hepatic fibrosis. Retardation of proliferation and clearance of activated HSCs from the injured liver is an appropriate therapeuticstrategy for the resolution and treatment of hepatic fibrosis. Clearance of activated HSCs from the injuredliver by autophagy inhibitors, proapoptotic agents and senescence inducers with the high affinity towardthe activated HSCs may be the novel therapeutic strategy for the treatment of hepatic fibrosis in the nearfuture.展开更多
Comprehensive understanding and possible control of parametric instabilities in the context of inertial confinement fusion (ICF) remains achallenging task. The details of the absorption processes and the detrimental e...Comprehensive understanding and possible control of parametric instabilities in the context of inertial confinement fusion (ICF) remains achallenging task. The details of the absorption processes and the detrimental effects of hot electrons on the implosion process require as mucheffort on the experimental side as on the theoretical and simulation side. This paper describes a proposal for experimental studies on nonlinearinteraction of intense laser pulses with a high-temperature plasma under conditions corresponding to direct-drive ICF schemes. We propose todevelop a platform for laser-plasma interaction studies based on foam targets. Parametric instabilities are sensitive to the bulk plasma temperatureand the density scale length. Foam targets are sufficiently flexible to allow control of these parameters. However, investigationsconducted on small laser facilities cannot be extrapolated in a reliable way to real fusion conditions. It is therefore necessary to performexperiments at a multi-kilojoule energy level on medium-scale facilities such asOMEGAor SG-III. An example of two-plasmon decay instabilityexcited in the interaction of two laser beams is considered.展开更多
α-MoO_3 ordered nanosheets have been synthesized under hydrothermal conditions using commercial MoO_3 and hydroquinone as structuring agent. X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission ...α-MoO_3 ordered nanosheets have been synthesized under hydrothermal conditions using commercial MoO_3 and hydroquinone as structuring agent. X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscopy(TEM) were used to analyse the obtained material. The conductivity mechanism of the Molybdenum ordered nanosheets has been investigated using combined complex impedance and modulus formalism.The temperature dependence of the conductivity, which was between 473 and 573 K, is very close to the Arrhenius' law, with an activation energy of 0.76 eV. However, the conductivity of the material increases with temperature. It shows a typical negative temperature coefficient resistance(NTCR) similar to that of a semiconductor. The dielectric properties of the MoO_3 compound have been studied in the temperature range of 473-573 K as well as the frequency range of 10 Hz to 13 MHz. The ac-conductivity for high frequency σac(ω)obeys the universal power law.展开更多
In order to combat the counterfeiting of drugs, adapted HPLC analytical USP methods were applied to evaluate the quality of the amoxicillin (with or without potassium clavulanate) powder for suspension sold in some Co...In order to combat the counterfeiting of drugs, adapted HPLC analytical USP methods were applied to evaluate the quality of the amoxicillin (with or without potassium clavulanate) powder for suspension sold in some Congolese markets. The adaptation has been done by modifying the column dimensions and adjusting the flow rate. According to the intended deployment of these methods in Democratic Republic of Congo (DRC), 3 factors (analyst, day and equipment) were involved in the validation step while applying the classic total error measurement approach with an accuracy profile as decision tool. Since adequate results were obtained in terms of selectivity, precision, trueness and accuracy (tolerance limits of life expectancy: ?6.0% and 3.8%) for levels of interest concentration, the methods have been considered for routine use on several samples from different provenances and collected in 4 major DRC cities. Out of 278 samples collected, 200 were eligible for analysis from which 28% were found under standards with several figures: pH failure, out of specification for amoxicillin content, absence of potassium clavulanate, physical modifications of the powders. As evidenced by these findings, medicines of low-quality continue to be a major public health problem requiring appropriate action to effectively address this problem.展开更多
In Heterogeneous Networks (HetNets), Integrating Device-to-Device communication (D2D) techniques presents as a promising solution for improving system performance by offloading traffic from heavily loaded macro cell (...In Heterogeneous Networks (HetNets), Integrating Device-to-Device communication (D2D) techniques presents as a promising solution for improving system performance by offloading traffic from heavily loaded macro cell (MC) to small cells (SCs). For instance, D2D can be used to offload traffic from heavily-loaded cells to light-loaded small cells. However, offloading new users may result in an unfair load distribution among small cells and consequently may affect the quality of service of some users. To achieve better performance and reduce blocking probability load balancing among small cells should be considered when we offload traffic from macro to small cells. In this paper, we consider a centralized offloaded relay selection scheme, in which a cellular provider can decide whether users can assist each other to relay their traffic to small cells. We propose a joint user-relay selection with dynamic load balancing scheme based on D2D communications using the Kuhn-Munkres (K-M) method. The offloading process considers the load from MC to SCs and among SCs. Compared to previous works, our simulation results show that the proposed scheme increases the number of admitted users in the system, and achieves a higher load balancing fairness index among small cells. Also, our scheme achieves a higher rate fairness index among users by adjusting the signal to interference plus noise ratio (SINR) threshold.展开更多
基金funding via EUROfusion Enabling research Project No.AWP21-ENR-01-CEA-02“Advancing Shock Ignition for Direct-Drive Inertial Fusion,”the framework of the EUROfusion Consortium,funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No.101052200-EUROfusion)+2 种基金the Czech Ministry of Education,Youth and Sports (CMEYS) for funding the operation of the PALS facility (Grant No.LM2023068)the EuroHPC Joint Undertaking for awarding access to Karolina at IT4Innovations (VSB-TU),Czechia under Project No.EHPC-REG-2023R02-006(DD-23-157)the Ministry of Education,Youth and Sports of the Czech Republic through e-INFRA CZ (Grant No.ID:90140)
文摘We investigate the spatial and temporal correlations of hot-electron generation in high-intensity laser interaction with massive and thin copper targets under conditions relevant to inertial confinement fusion.Using Ka time-resolved imaging,it is found that in the case of massive targets,the hot-electron generation follows the laser pulse intensity with a short delay needed for favorable plasma formation.Conversely,a significant delay in the x-ray emission compared with the laser pulse intensity profile is observed in the case of thin targets.Theoretical analysis and numerical simulations suggest that this is related to radiation preheating of the foil and the increase in hot-electron lifetime in a hot expanding plasma.
基金supported by the National Key R&D Program of China(Grant No.2022YFB4600300)the National Natural Science Foundation of China(No.U22A20189,52175364)the China Scholarship Council(Grant No.202206290134)。
文摘Nd-Fe-B permanent magnets play a crucial role in energy conversion and electronic devices.The essential magnetic properties of Nd-Fe-B magnets,particularly coercivity and remanent magnetization,are significantly infuenced by the phase characteristics and microstructure.In this work,Nd-Fe-B magnets were manufactured using vacuum induction melting(VIM),laser directed energy deposition(LDED)and laser powder bed fusion(LPBF)technologies.Themicrostructure evolution and phase selection of Nd-Fe-B magnets were then clarified in detail.The results indicated that the solidification velocity(V)and cooling rate(R)are key factors in the phase selection.In terms of the VIM-casting Nd-Fe-B magnet,a large volume fraction of theα-Fe soft magnetic phase(39.7 vol.%)and Nd2Fe17Bxmetastable phase(34.7 vol.%)areformed due to the low R(2.3×10-1?C s-1),whereas only a minor fraction of the Nd2Fe14B hard magnetic phase(5.15 vol.%)is presented.For the LDED-processed Nd-Fe-B deposit,although the Nd2Fe14B hard magnetic phase also had a low value(3.4 vol.%)as the values of V(<10-2m s-1)and R(5.06×103?C s-1)increased,part of theα-Fe soft magnetic phase(31.7vol.%)is suppressed,and a higher volume of Nd2Fe17Bxmetastable phases(47.5 vol.%)areformed.As a result,both the VIM-casting and LDED-processed Nd-Fe-B deposits exhibited poor magnetic properties.In contrast,employing the high values of V(>10-2m s-1)and R(1.45×106?C s-1)in the LPBF process resulted in the substantial formation of the Nd2Fe14B hard magnetic phase(55.8 vol.%)directly from the liquid,while theα-Fe soft magnetic phase and Nd2Fe17Bxmetastable phase precipitation are suppressed in the LPBF-processed Nd-Fe-B magnet.Additionally,crystallographic texture analysis reveals that the LPBF-processedNd-Fe-B magnets exhibit isotropic magnetic characteristics.Consequently,the LPBF-processed Nd-Fe-B deposit,exhibiting a coercivity of 656 k A m-1,remanence of 0.79 T and maximum energy product of 71.5 k J m-3,achieved an acceptable magnetic performance,comparable to other additive manufacturing processed Nd-Fe-B magnets from MQP(Nd-lean)Nd-Fe-Bpowder.
文摘Background: The investigation of toxin genes in strains involved in staphylococcal food poisoning contributes to food safety. The aim of this study was to isolate and identify enterotoxigenic Staphylococcus strains from dried, smoked, and braised fish sold in Ouagadougou markets. Methodology: Staphylococci were isolated using standard microbiology methods. Staphylococcus strains were identified using API Staph kit (Reference # 20500, BioMerieux S.A., Marcy l'Etoile, France). The molecular identification of isolated Staphylococcus aureus strains was specifically confirmed by PCR using the Staur4 and Staur6 primers. The genes encoding enterotoxins, enterotoxin-like toxins, exfoliative toxins, and TSST-1 toxin were detected by multiplex PCR using specific primers from Inquaba Biotec West Africa Ltd, Africa's Genomics Company. Results: The results of the microbiological quality assessment indicated that most of the samples analyzed were found to be of unsatisfactory microbiological quality according to the Staphylococcus aureus microbiological criteria (m = 102). Overall, only 12.55% of samples were satisfactory, while 97.45% were unsatisfactory. The STAPH API gallery allowed the identification of the following species: Staphylococcus aureus, Staphylococcus xylosus, Staphylococcus lugdunensis, Staphylococcus hominis, Staphylococcus haemolyticus, Staphylococcus lentus, Staphylococcus sciuri and Staphylococcus capitis. Of the 108 Staphylococcus isolates, 81 (75%) showed at least one (1) toxin gene. Among the 21 toxin genes tested in this study, 20 genes were detected in all strains analyzed. The staphylococcal toxin genes detected were present in both Staphylococcus aureus and the other coagulase-negative strains isolated in this study. In addition, these genes are found individually or in association in certain strains. The most frequent genes detected in toxin gene-positive strains were: the tsst-1 gene in 45 isolated strains (41.7%), sei (16/14.8%), seg (13/12%), ser (7/6.5%) sec (6/5.5%), and sea (5/4.6%) for staphylococcal enterotoxins, seln (14/12.9%), selq (8/7.4%), for enterotoxin-like toxin gene and eta (3/2.7%) for exfoliative toxin genes. Conclusion: This study highlighted the pathogenicity of Staphylococcus strains isolated from dried, smoked, and braised fish sold in Ouagadougou markets. Monitoring toxin-producing strains of Staphylococcus is invaluable for better prevention of food poisoning.
基金supported by the Research Funds of Institute of Zhejiang University-Quzhou(IZQ2023RCZX032)the Natural Science Foundation of Guangdong Province(2022A1515010185)+1 种基金the Fundamental Research Funds for the Central Universities(FRF-TP-20-005A3)partially supported by the Special Funds for Postdoctoral Research at Tsinghua University(100415017)。
文摘Electrocatalytic water splitting is crucial for H2generation via hydrogen evolution reaction(HER)but subject to the sluggish dynamics of oxygen evolution reaction(OER).In this work,single Fe atomdoped MoS_(2)nanosheets(SFe-DMNs)were prepared based on the high-throughput density functional theory(DFT)calculation screening.Due to the synergistic effect between Fe atom and MoS_(2)and optimized intermediate binding energy,the SFe-DMNs could deliver outstanding activity for both HER and OER.When assembled into a two-electrode electrolytic cell,the SFe-DMNs could achieve the current density of 50 mA cm^(-2)at a low cell voltage of 1.55 V under neutral condition.These results not only confirmed the effectiveness of high-throughput screening,but also revealed the excellent activity and thus the potential applications in fuel cells of SFe-DMNs.
文摘This study presents a contribution to the development of a model for vegetable oil droplets vaporization, with a particular focus on the influence of the experimental set-up for their use as fuel in diesel engines. Two systems were considered: an open-environment system obtained through a hot gas flow, and a closed-environment system. Vaporization was conducted under identical conditions, with the results subsequently compared. The findings indicate that, for temperatures between 473 K and 673 K, droplets behaviour in both systems presents only a heating and expansion phase. For temperatures above 673 K, the behaviour of the droplets differs between the devices. In the open environment device, a linear reduction in droplets diameter is observed following the transient phase, suggesting stationary vaporization and enabling the calculation of a vaporization constant and the well-known D2 law is respected. In the closed-environment device, puffing, micro-explosions and gas ejections are observed, and it is not possible to determine vaporization constant and D2 law is not respected. The results demonstrate the necessity of developing a model for the thermal decomposition of vegetable oil before attempting to create a model for the vaporization of these oils. In order to achieve this, it is essential to construct an experimental setup that more closely emulates the real conditions within the combustion chamber of a diesel engine, taking into account the variables of pressure, temperature and the heating process.
基金Z.Y.acknowledges the National Natural Science Foundation of China(Grant No.42074211).
文摘Magnetic reconnection and dipolarization are crucial processes driving magnetospheric dynamics,including particle energization,mass circulation,and auroral processes,among others.Recent studies have revealed that these processes at Saturn and Jupiter are fundamentally different from the ones at Earth.The reconnection and dipolarization processes are far more important than previously expected in the dayside magnetodisc of Saturn and potentially Jupiter.Dayside magnetodisc reconnection was directly identified by using Cassini measurements(Guo RL et al.,2018b)and was found to be drizzle-like and rotating in the magnetosphere of Saturn(Delamere et al.,2015b;Yao ZH et al.,2017a;Guo RL et al.,2019).Moreover,magnetic dipolarization could also exist at Saturn’s dayside(Yao ZH et al.,2018),which is fundamentally different from the terrestrial situation.These new results significantly improve our understanding of giant planetary magnetospheric dynamics and provide key insights revealing the physics of planetary aurorae.Here,we briefly review these recent advances and their potential implications for future investigations.
基金Project supported by the Occitanie region(RETREAt project-ALDOCT 000443)the French geological survey(BRGM)。
文摘This study proposes an advanced leaching method using organic acids to recover rare earth elements(REEs)from NdFeB permanent magnets from end-of-life computers hard disk drives(HDDs).The end-oflife HDDs were first dismantled in order to recover NdFeB magnets,which were then thermally demagnetized at 350℃during 30 min before crushing in a ball mill under inert atmosphere.Scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS)analyses performed on the NdFeB magnets show the heterogeneous structure containing the major matric phase Nd_(2)Fe_(14)B and the REEsrich phase containing Nd and Pr oxides.Additionally,X-ray diffraction(XRD)and Mossbauer spectroscopy(MS)analyses on the ground NdFeB magnet show that grinding NdFeB magnets under inert atmosphere helps to minimize its oxidation.Chemical analysis shows that the composition of the ground sample is Nd:22.8 wt%,Pr:3.3 wt%,Dy:1.2 wt%,Fe:62.6 wt%,Co:1.5 wt%,B:0.9 wt%,Ni:0.6 wt%.Diagrams of speciation and equilibrium phases(E_(h) vs.pH)were calculated to determine the predominance of the formed species in the REEs-organic acids systems.The influence of the organic acid type(acetic acid,formic acid,citric acid and tartaric acid),the acid concentration(10 vol%,up to saturation),and the solid/liquid(S/L)ratio(0.5%-10%)on NdFeB magnets leaching was investigated employing an optimal experimental design conceived by the statistical software JMP.Acetic acid(CH_(3)COOH)shows the highest leaching performance of REEs,allowing leaching yields over 90%for Nd,Dy and Pr in the acid concentration range of 1.6-10 mol/L and the S/L ratio range of 0.5%-5%at a temperature of 60℃.The results presented in this investigation suggest that REEs can be recovered from magnets of end-of-life HDDs using an eco-friendly method assisted by organic acids.
文摘Hydrogen absorption and desorption characteristics for high coercivity NdDyFeCoNbCuB sintered bulk magnets were studied, by differential scanning calorimetry （DSC） measurement and hydrogenation kinetics measurement. The DSC measurements showed that hydrogenation of Nd-rich phase occurred in the temperature range of 40-185 ℃, hydrogenation of the tetragonal （Ф） phase in the temperature range of 185-220 ℃, as well as the disproportionation of the Ф phase that occurred in a broad temperature range from around 500 to 800 ℃. The hydrogenation kinetics measurements indicated that hydrogen absorption of the bulk magnets at 50 ℃ absorbed more hydrogen than at 150 ℃, although this procedure was slower at 50 ℃ than at 150℃. This phenomenon was discussed by means of pressure-concentration-temperature （p-c-T） diagrams.
基金supported in part by Zhejiang Provincial Key Research and Development Program(2018C01084)Zhejiang Natural Science Foundation(LQ20F020009)Zhejiang Gongshang University,Zhejiang Provincial Key Laboratory of New Network Standards and Technologies(2013E10012)。
文摘Deadlock resolution strategies based on siphon control are widely investigated.Their computational efficiency largely depends on siphon computation.Mixed-integer programming(MIP)can be utilized for the computation of an emptiable siphon in a Petri net(PN).Based on it,deadlock resolution strategies can be designed without requiring complete siphon enumeration that has exponential complexity.Due to this reason,various MIP methods are proposed for various subclasses of PNs.This work proposes an innovative MIP method to compute an emptiable minimal siphon(EMS)for a subclass of PNs named S^(4)PR.In particular,many particular structural characteristics of EMS in S4 PR are formalized as constraints,which greatly reduces the solution space.Experimental results show that the proposed MIP method has higher computational efficiency.Furthermore,the proposed method allows one to determine the liveness of an ordinary S^(4)PR.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China(Grant Nos.LY20E010002,LR18E010001,and LD19E010001)the National Natural Science Foundation of China(Grant Nos.U1704253 and 51801047)+2 种基金Liaoning Revitalization Talents Program(Grant No.XLYC1807177)the Key Research and Development plan of Zhejiang Province,China(Grant No.2020C05014)Ten Thousand Talents Plan of Zhejiang Province,China(Grant No.2018R52003)。
文摘This review summarizes the recent advances on the application of ^(57)Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine structures of the Ce_(2)Fe_(14)B,(Ce,Nd)_(2)Fe_(14)B and MM_(2)Fe_(14)B phases are well-defined by using the model based on the Wigner-Seitz analysis of the crystal structure. The results show that the isomer shift δ and the quadrupole splitting öEQ of those 2:14:1 phases show minor changes with the Nd content, while the hyperfine field Bhfincreases monotonically with increasing Nd content and its value is influenced by the element segregation and phase separation in the 2:14:1 phase. Then, the hyperfine structures of the low fraction secondary phases are determined by the ^(57)Fe Mössbauer spectrometry due to its high sensitivity. On this basis,the content, magnetic behavior, and magnetization of the REFe_(2) phase, the amorphous grain boundary(GB) phase, and the amorphous worm-like phase, as well as their effects on the magnetic properties, are systematically studied.
文摘A novel statistical approach to evaluate the manufacturing quality of press coated tablets in terms of the centering of their core is presented. We also provide a formula to determine the necessary sample size. This approach is applied to real data.
文摘We introduce a new approach to image super-resolution. The idea is to use a simple wavelet-based linear interpolation scheme as our initial estimate of high-resolution image;and to intensify geometric structure in initial estimation with an iterative projection process based on hard-thresholding scheme in a new angular multiselectivity domain. This new domain is defined by combining of laplacian pyramid and angular multiselectivity decomposition, the result is multiselective contourlets which can capture and restore adaptively and slightly better geometric structure of image. The experimental results demonstrate the effectiveness of the proposed approach.
文摘Mobile games are gaining in popularity among students, although the factors driving engagement remain poorly understood. This study, conducted among 378 students studying for a Bachelor’s degree in Computer and Digital Sciences at the Université Virtuelle de Côte d’Ivoire, explores the influence of game assets and colours on player engagement. Using an online questionnaire, the study identified students’ gaming preferences and their perception of colours. The results show that the key elements most favoured by students are graphics, sound design, the game system, narrative, interactivity and accessibility. What’s more, colour plays a decisive role in their preferences and commitment to educational mobile games.
文摘Mixed convection of heat and mass transfer in an isosceles trapezoidal cavity has been studied numerically. Constant heat flux is imposed through four outlets and the grid is insulated. The inclined walls are maintained in natural convection while the lower horizontal wall is adiabatic. These conditions reflect the air draft zone of the ASUTO charcoal stove. The governing two-di- mensional flow equations have been solved by using the finite difference method and Thomas’s algorithm. The investigations are conducted for different values of Richardson (R<sub>i</sub>), Reynolds number (R<sub>e</sub>) and inclination angles of sidewalls. The results are presented in terms of streamlines, isotherms, moisture contours. It was found that for Reynolds number (R<sub>e</sub>) equal to 100, the flow pattern is strongly dependent on the inclination angle and Richardson number. Thus, for high Richardson number (R<sub>i</sub>) values (10, 100), the dominance of natural convection over the flow structure decreases with the decreasing of the inclination angle of sidewalls of the cavity. For R<sub>i</sub> = 1, an optimum air draft corresponds to an inclination angle in the vicinity of 22° while for R<sub>i</sub> = 10 or 100 (in dominance of natural convection), the optimum inclination angle for air draft is in the vicinity of 15°.
文摘Hepatic fibrosis is a pathological lesion, characterized by the progressive accumulation of extracellularmatrix （ECM） in the perisinusoidal space and it is a major problem in chronic liver diseases. Phenotypicactivation of hepatic stellate cells （HSC） plays a central role in the progression of hepatic fibrosis. Retardation of proliferation and clearance of activated HSCs from the injured liver is an appropriate therapeuticstrategy for the resolution and treatment of hepatic fibrosis. Clearance of activated HSCs from the injuredliver by autophagy inhibitors, proapoptotic agents and senescence inducers with the high affinity towardthe activated HSCs may be the novel therapeutic strategy for the treatment of hepatic fibrosis in the nearfuture.
基金The authors acknowledge support from the European Regional Development Fund for the following projects:HiFI(No.CZ.02.1.01/0.0/0.0/15_003/0000449),CAAS(No.CZ.02.1.01/0.0/0.0/16_019/0000778),ADONIS(No.CZ.02.1.01/0.0/0.0/16_019/0000789),and ELITAS(No.CZ.02.1.01/0.0/0.0/16_013/0001793)This work has received funding from the European Union Horizon 2020 Research and Innovation Programme under Grant Agreement No.633053(EUROfusion Project No.CfP-AWP17-IFE-CEA-01)+2 种基金Computational resources were provided by the MetaCentrum under the LM2010005 projectIT4InnovationsCentre of Excellence under the CZ.1.05/1.1.00/02.0070 and LM2011033 projectsthe ECLIPSE cluster of ELI-Beamlines.The EPOCH code was developed as part of the UK EPSRC-funded EP/G054940/1 project.
文摘Comprehensive understanding and possible control of parametric instabilities in the context of inertial confinement fusion (ICF) remains achallenging task. The details of the absorption processes and the detrimental effects of hot electrons on the implosion process require as mucheffort on the experimental side as on the theoretical and simulation side. This paper describes a proposal for experimental studies on nonlinearinteraction of intense laser pulses with a high-temperature plasma under conditions corresponding to direct-drive ICF schemes. We propose todevelop a platform for laser-plasma interaction studies based on foam targets. Parametric instabilities are sensitive to the bulk plasma temperatureand the density scale length. Foam targets are sufficiently flexible to allow control of these parameters. However, investigationsconducted on small laser facilities cannot be extrapolated in a reliable way to real fusion conditions. It is therefore necessary to performexperiments at a multi-kilojoule energy level on medium-scale facilities such asOMEGAor SG-III. An example of two-plasmon decay instabilityexcited in the interaction of two laser beams is considered.
文摘α-MoO_3 ordered nanosheets have been synthesized under hydrothermal conditions using commercial MoO_3 and hydroquinone as structuring agent. X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscopy(TEM) were used to analyse the obtained material. The conductivity mechanism of the Molybdenum ordered nanosheets has been investigated using combined complex impedance and modulus formalism.The temperature dependence of the conductivity, which was between 473 and 573 K, is very close to the Arrhenius' law, with an activation energy of 0.76 eV. However, the conductivity of the material increases with temperature. It shows a typical negative temperature coefficient resistance(NTCR) similar to that of a semiconductor. The dielectric properties of the MoO_3 compound have been studied in the temperature range of 473-573 K as well as the frequency range of 10 Hz to 13 MHz. The ac-conductivity for high frequency σac(ω)obeys the universal power law.
文摘In order to combat the counterfeiting of drugs, adapted HPLC analytical USP methods were applied to evaluate the quality of the amoxicillin (with or without potassium clavulanate) powder for suspension sold in some Congolese markets. The adaptation has been done by modifying the column dimensions and adjusting the flow rate. According to the intended deployment of these methods in Democratic Republic of Congo (DRC), 3 factors (analyst, day and equipment) were involved in the validation step while applying the classic total error measurement approach with an accuracy profile as decision tool. Since adequate results were obtained in terms of selectivity, precision, trueness and accuracy (tolerance limits of life expectancy: ?6.0% and 3.8%) for levels of interest concentration, the methods have been considered for routine use on several samples from different provenances and collected in 4 major DRC cities. Out of 278 samples collected, 200 were eligible for analysis from which 28% were found under standards with several figures: pH failure, out of specification for amoxicillin content, absence of potassium clavulanate, physical modifications of the powders. As evidenced by these findings, medicines of low-quality continue to be a major public health problem requiring appropriate action to effectively address this problem.
文摘In Heterogeneous Networks (HetNets), Integrating Device-to-Device communication (D2D) techniques presents as a promising solution for improving system performance by offloading traffic from heavily loaded macro cell (MC) to small cells (SCs). For instance, D2D can be used to offload traffic from heavily-loaded cells to light-loaded small cells. However, offloading new users may result in an unfair load distribution among small cells and consequently may affect the quality of service of some users. To achieve better performance and reduce blocking probability load balancing among small cells should be considered when we offload traffic from macro to small cells. In this paper, we consider a centralized offloaded relay selection scheme, in which a cellular provider can decide whether users can assist each other to relay their traffic to small cells. We propose a joint user-relay selection with dynamic load balancing scheme based on D2D communications using the Kuhn-Munkres (K-M) method. The offloading process considers the load from MC to SCs and among SCs. Compared to previous works, our simulation results show that the proposed scheme increases the number of admitted users in the system, and achieves a higher load balancing fairness index among small cells. Also, our scheme achieves a higher rate fairness index among users by adjusting the signal to interference plus noise ratio (SINR) threshold.
