Coal wall stability is a critical factor influencing coal mining efficiency and threatens the safety of working faces,where irregular coal wall surfaces significantly affect the contact and support effectiveness of th...Coal wall stability is a critical factor influencing coal mining efficiency and threatens the safety of working faces,where irregular coal wall surfaces significantly affect the contact and support effectiveness of the support plate,thereby impacting stability.Through a combination of theoretical analysis,mechanical testing,and numerical simulations,this study establishes a mechanical model of irregular coal wall surfaces to investigate the effects of the undulation period and undulation height on coal wall failure characteristics.This research reveals the mechanical response mechanisms of irregular coal wall surfaces and proposes an innovative method to enhance coal wall stability by improving the supporting cushion material of the support plate,which was validated through numerical simulations.The results show that the undulation height and undulation period significantly influence the macroscopic mechanical parameters of the samples,with the undulation height exerting a more pronounced effect.The strength of the samples with undulating surfaces is approximately 50%-60% that of the samples with flat surfaces.The failure mode under uniaxial compression is predominantly tensile,resulting in long and slender block fragments with a characteristic“Ⅲ”-shaped tensile fracture pattern.During the loading process,samples with undu-lating surfaces dissipate energy at all stages,with a greater proportion of energy dissipation occurring during the early loading stage because of structural damage and the formation of internal cracks.The surface compressive and tensile stresses are correlated with the curvature radius of the convex surface and the elastic modulus of the supporting plate.Reducing the elastic modulus of the supporting plate material can effectively alleviate the stress concentration at convex locations and increase the peak strength.This study provides theoretical foundations and technical references for the prevention and control of coal wall spalling in deep thick coal seam mining.展开更多
A theoretical study of the influence of a quasi-electrostatic support on the amplification level of the slow space charge wave(SCW) in the amplification section of a superheterodyne free electron laser(FEL) was carrie...A theoretical study of the influence of a quasi-electrostatic support on the amplification level of the slow space charge wave(SCW) in the amplification section of a superheterodyne free electron laser(FEL) was carried out. One of the ways to significantly increase the saturation level of the slow SCW is maintaining the conditions of a three-wave parametric resonance between the slow, fast SCWs and the resulting pump electric field. This can be done by introducing the quasielectrostatic support in the superheterodyne FEL amplification section. Also, it was found that the generated pump electric field significantly influences the maintenance of parametric resonance conditions. As a result, this increases the saturation level of the slow SCW by 70%. Finally, the quasi-electrostatic support significantly reduces the maximum value of the electrostatic undulator pump field strength, which is necessary to achieve the maximum saturation level of the slow SCW.展开更多
This study evaluates the physical mechanisms of incident waves as they interact with a porous wavy barrier of finite thickness.A wave-trapping chamber is formed between the thick wavy barrier(TWB)and partially reflect...This study evaluates the physical mechanisms of incident waves as they interact with a porous wavy barrier of finite thickness.A wave-trapping chamber is formed between the thick wavy barrier(TWB)and partially reflecting seawall(PRS).The effect of seabed undulations is incorporated into the wave-trapping analysis of the TWB.The boundary value problem proposed in this study is solved using a multidomain boundary element method within the context of linear potential flow theory.Coefficients such as reflection,runup,horizontal force on PRS,and vertical force on TWB are examined for various structural configurations.The position of seabed undulations is analyzed for four scenarios:i)seabed undulations upwave of the wavy barrier with a trapping chamber,ii)seabed undulations upwave of the wavy barrier without a trapping chamber,iii)seabed undulations underneath the wavy barrier with a trapping chamber,and iv)seabed undulations beneath the wavy barrier without a trapping chamber.The study results are compared with known results to verify their accuracy.The effects of PRS,TWB porosity,trapping chamber,plate thickness,seabed type,and submergence depth on hydrodynamic coefficients are analyzed against relative water depth.The study reveals that the introduction of a porous TWB with a trapping chamber results in minimal hydrodynamic coefficients(reduced reflection and force on a wall)compared to a rigid TWB without a trapping chamber.A comparison of various seabeds is reported for all combinations of TWB with a chamber.The sloping seabed upwave of the barrier with a trapping chamber,20%plate porosity,and 50%wall reflection at an appropriate submergence depth could replace gravity-type breakwaters in deeper waters.This study holds great potential for analyzing wave trapping coefficients by TWB to provide an effective coastal protection system.展开更多
A new on-chip light source configuration has been proposed,which utilizes the interaction between a microwave or laser and a dielectric nanopillar array to generate a periodic electromagnetic near-field and applies pe...A new on-chip light source configuration has been proposed,which utilizes the interaction between a microwave or laser and a dielectric nanopillar array to generate a periodic electromagnetic near-field and applies periodic transverse acceleration to relativistic electrons to generate high-energy photon radiation.The dielectric nanopillar array interacting with the driving field acts as an electron undulator,in which the near-field drives electrons to oscillate.When an electron beam propagates through this nanopillar array in this light source configuration,it is subjected to a periodic transverse near-field force and will radiate X-ray or evenγ-ray high-energy photons after a relativistic frequency up-conversion.Compared with the undulator which is based on the interaction between strong lasers and nanostructures to generate a plasmonic near-field,this configuration is less prone to damage during operation.展开更多
The effects of nanostructuring on the mechanical and dry-sliding wear behaviors of a FeCoNi medium-entropy alloy(MEA)were systematically investigated through nano-indentation and ball-on-disc wear tests.The results sh...The effects of nanostructuring on the mechanical and dry-sliding wear behaviors of a FeCoNi medium-entropy alloy(MEA)were systematically investigated through nano-indentation and ball-on-disc wear tests.The results show that reducing the grain size down into the nano-meter regime,on the one hand,significantly elevates the hardness of the FeCoNi alloy,and on the other hand,facilitates the formation of a surface oxide layer.As a result,the wear rate of the nanocrystalline(NC)FeCoNi alloy is one order of magnitude lower than its coarse-grained counterpart.The NC FeCoNi alloy also exhibits obviously enhanced wear resistance compared with conventional NC Ni and Ni-based alloys in terms of both lower wear rate and friction coefficient.Such enhancement in tribological properties mainly stems from the improved strain hardening ability,owing to the inevitable concentration heterogeneity in MEA that imposes extra resistance to dislocation motion.展开更多
The helical undulator is in high demand in synchrotron radiation facilities for circular polarization generation.Owing to the higher field strength provided by the superconducting undulator compared to the conventiona...The helical undulator is in high demand in synchrotron radiation facilities for circular polarization generation.Owing to the higher field strength provided by the superconducting undulator compared to the conventional permanent-magnet undulator,greater research efforts should be directed toward this area.The helical superconducting undulator holds great potential in synchrotron radiation facilities,especially in low-energy storage rings that seek circularly polarized radiation with the highest possible radiation flux.Following the successful development of planar superconducting undulators,the Institute of High Energy Physics conducted research and development for the helical superconducting undulator.A 0.5-m-long Deltatype superconducting undulator prototype was developed and tested.Detailed information on the design,fabrication,and cryogenic testing of the prototype is presented and discussed.展开更多
Geode, boudinage, and undulation structures are widely distributed in the siliceous beds of the Upper Cretaceous/Tertiary rocks in Jordan. Their formation was attributed to tectonic forces, syngenetic processes, organ...Geode, boudinage, and undulation structures are widely distributed in the siliceous beds of the Upper Cretaceous/Tertiary rocks in Jordan. Their formation was attributed to tectonic forces, syngenetic processes, organic disintegration processes, subaquatic gliding, compaction and settlement, and meteoritic impacts. In this work, the structural features in the siliceous beds of Jordan are attributed to an interplay of load and directed pressures, and mineralogical transformation processes (opal-A to opal-CT to quartz), governed by pH changes. Tectonic directed pressure was acting in an ESE-WSW direction and is common in the silicified limestone of Upper Cretaceous.展开更多
High-accuracy geoid determination is an essential goal that many groups of scientists and countries are striving to achieve. Techniques for determining geoid models have evolved over time. Unfortunately, this all-impo...High-accuracy geoid determination is an essential goal that many groups of scientists and countries are striving to achieve. Techniques for determining geoid models have evolved over time. Unfortunately, this all-important determination requires relatively substantial technical and financial resources, depending on the type of geoid to be determined. This situation justifies the inadequacy, and sometimes absence, of accurate geoid models in many countries, despite the new challenges of altimetric positioning using space or satellite positioning techniques. This study focuses on the establishment of a geometric geoid model using simplistic techniques that are accessible and applicable in restricted or wide areas, with or without gravimetric data. The study was applied to the Dakar-Thiès-Mbour triangle, the two regions in the extreme west of Senegal that are home to the most infrastructure projects with the highest socio-economic stakes, as well as mines currently being exploited, and therefore the highest stakes in terms of positioning. This study also enabled us to assess the accuracy of a number of global field models in Senegal, which are used by some professionals for altimetric positioning using Global Positioning Satellite Systems (GNSS) in the absence of a local geoid model. The estimated geoid model is based on the determination of undulation at various sample points in the study area. To this end, a campaign of GNSS observations and direct levelling was carried out on the various points spread across the study area. These measurements were then used to determine the undulation at each point. Bilinear interpolation was used to deduce the undulations throughout the study area, based on the altimeter conversion grid. This grid was evaluated using GPS/level control points.展开更多
ICF(inertial confinement fusion)holds significant potential for achieving controlled nuclear fusion,but challenges related to efficient energy transfer and plasma stabilization remains.This article explores the ion-bu...ICF(inertial confinement fusion)holds significant potential for achieving controlled nuclear fusion,but challenges related to efficient energy transfer and plasma stabilization remains.This article explores the ion-bubble trigger mechanism as a promising solution for improving the compression and energy deposition processes in ICF,particularly when coupled with external magnetic fields,wigglers,undulators,and trapped magnetic fields.The ion-bubble mechanism enhances energy transfer by creating localized heating in the plasma,increasing the likelihood of fusion ignition.External magnetic fields,through their interaction with plasma particles,can optimize ion-bubble interactions by influencing particle trajectories and stabilizing plasma instabilities.Additionally,wigglers and undulators—devices that create oscillating magnetic fields—offer a means to fine-tune the interaction between plasma and electromagnetic radiation,further enhancing the ion-bubble effect.Trapped magnetic fields,formed through plasma compression,also contribute to plasma confinement and stability,offering further support for the ion-bubble trigger mechanism.By combining these factors,the ion-bubble trigger mechanism in ICF could significantly improve fusion efficiency and bring us closer to realizing sustainable fusion energy.展开更多
Brucellosis is an old,infectious and common zoonosis whose causative agents are Gramnegative bacteria from the Brucella genus.Brucellosis is transmitted through direct contactwith infected animals or using unpasteuriz...Brucellosis is an old,infectious and common zoonosis whose causative agents are Gramnegative bacteria from the Brucella genus.Brucellosis is transmitted through direct contactwith infected animals or using unpasteurized dairy products of goats,pigs,camels,sheep,buffalo and cows.Brucellosis is still the most common zoonosis in the world,with mostof cases occurring in developing countries.Today,an approach to traditional medicine andmedicinal plants,especially with regards to the repeated recommendations of the World HealthOrganization,is a necessity.One-third of chemical drugs are produced by using plants andthere is a high potential to produce more drugs from plants.Medicinal plants are helpful inthe management of various conditions,especially bacterial diseases.Although there is notenough scientific evidence regarding the clinical effectiveness of herbal drugs for the treatmentof brucellosis,there is strong evidence on the antimicrobial effects of herbal drugs to preventinfection.Therefore,this article seeks to describe the antibacterial effects of some plantderived essential oils or extracts,so that they can serve as promising choices to develop newanti-Brucella medications,as suitable alternatives to conventional antibiotics for brucellosis,asmuch as possible,taking into account the benefits of these herbal drugs.展开更多
Engineering seismic exploration aims at shallow imaging which is confused by statics if the surface is uneven. Direct pre-stack depth migration （DPDM） is based on accurate elevations of sources and receivers, by whi...Engineering seismic exploration aims at shallow imaging which is confused by statics if the surface is uneven. Direct pre-stack depth migration （DPDM） is based on accurate elevations of sources and receivers, by which static correction is completely abandoned before migration and surely the imaging quality is remarkably improved. To obtain some artificial shot gathers, high-order staggered-grid finite-difference （FD） method is adapted to model acoustic wave propagation. Since the shot gathers are always disturbed by regular interferences, the statics still must be applied to supporting the interference elimination by apparent velocity filtering method. Then all the shot gathers should be removed back to their original positions by reverse statics. Finally, they are migrated by pre-stack reverse-time depth migration and imaged. The numerical experiments show that the DPDM can ideally avoid the mistakes caused by statics and increase imaging precision.展开更多
Objective:To investigate the prevalence and risk factors of brucellosis in human and animal’s communities in southern Saudi Arabia.Methods:A cross-sectional sero-epidemiological study was conducted in Aseer and Jazan...Objective:To investigate the prevalence and risk factors of brucellosis in human and animal’s communities in southern Saudi Arabia.Methods:A cross-sectional sero-epidemiological study was conducted in Aseer and Jazan,Saudi Arabia(October 2017-October 2018).Human serum samples(n=339)were initially screened for Brucella antibodies and positive samples were further titrated for Brucella antibodies by immunocapture assay(titer of≥1:320 as positive).Animal samples(n=828)were screened using the Rose Bengal test.Relationship status was dichotomized to measure and predict independent contributions to variations in human using univariate and multivariate stepwise binary logistic regression model.Results:The rate of brucellosis among the 339 human samples in the two regions was 33.9%,and the rate of acute brucellosis was 12.4%.The rate of brucellosis in animals was 4.7%.Human brucellosis among the target groups was higher in northwestern Aseer(53.3%)compared to Southeastern Aseer(25.9%)and Jazan region(20.6%).The disease was more prevalent among non-Saudi nationals(35.2%)compared to Saudis(30.5%).The rate of brucellosis among butchers and shepherds was 37.5%and 37.2%,respectively.The rate of brucellosis was 37.8%in people over 30 years of age.Our univariate analysis showed that residing in Aseer region(OR:2.60,95%CI:1.50-4.40),especially residing in northwestern Aseer region(OR:4.40,95%CI:2.40-7.90),frequent consumption of raw meat(OR:2.90,95%CI:1.50-5.50),shepherds(OR:2.10,95%CI:0.80-5.30),owning sheep(OR:2.20,95%CI:1.10-4.40),daily contact with animals(OR:2.10,95%CI:0.75-5.80),and those>30-year-old(OR:1.50,95%CI:1.00-2.40)were significantly associated with increased risks of brucellosis.Our multivariate analysis further showed that residing in northwestern Aseer(OR:9.16,95%CI:3.39-24.76)and having sheep(OR:1.16,95%CI:1.00-1.35)were significant and independent risks of brucellosis while residing in agricultural region(OR:0.28,95%CI:0.10-0.78)was a significant and independent protector against brucellosis.Conclusions:The study concluded that residing in northwestern Aseer area and having animals(sheep)are associated with significantly increased risks of brucellosis.展开更多
Most of the current computing methods used to determine the magnetic field of a uniformly magnetized cuboid assume that the observation point is located in the upper half space without a source. However, such methods ...Most of the current computing methods used to determine the magnetic field of a uniformly magnetized cuboid assume that the observation point is located in the upper half space without a source. However, such methods may generate analytical singularities for conditions of undulating terrain. Based on basic geomagnetic field theories, in this study an improved magnetic field expression is derived using an integration method of variable substitution, and all singularity problems for the entire space without a source are discussed and solved. This integration process is simpler than that of previous methods, and final integral results with a more uniform form. AT at all points in the source-flee space can be calculated without requiring coordinate transformation; thus forward modeling is also simplified. Corresponding model tests indicate that the new magnetic field expression is more correct because there is no analytical singularity and can be used with undulating terrain.展开更多
First-break picking is the key step in seismic data processing for surveying undulate surfaces, and directly infl uences the precision of near-surface modeling and effects of static corrections. The current first-brea...First-break picking is the key step in seismic data processing for surveying undulate surfaces, and directly infl uences the precision of near-surface modeling and effects of static corrections. The current first-break auto-picking methods may fail when the signalto-noise ratio（SNR） is low for seismic data in the undulate area, and require labor and time intensive manual picking. This study develops an improved super-virtual interferometry（SVI） method that combines multichannel and multidomain quality control（MMQC） techniques to achieve auto-picked first breaks. The improved SVI method extends the SVI application to enhance the SNR for near-surface scattered waves for the first time, which allows for the SVI method to adapt to first breaks with complex raypaths by linear combination of refractions and near-surface scattered waves. Methods of inverse and multidomain interferometry are developed to effectively enhance the virtual records extracted by the SVI method. The deconvolution filter for waveforms is used to increase resolution and reduce false picks, while the MMQC technique is designed to auto-correct false picks and increase the stability of auto-picking first breaks. The robust technique developed in this study enables stable processing of large 3D seismic datasets. Higher quality results are obtained using the approach presented in this paper to actual field data from the mountain areas in western China, when compared to some commonly used commercial software.展开更多
基金the National Key Research and Development Program of China(Nos.2023YFC2907501 and 2023YFC2907503)the National Natural Science Foundation of China(Nos.52374106 and 52274154)the Fundamental Research Funds for the Central Universities(No.2023YQTD02).
文摘Coal wall stability is a critical factor influencing coal mining efficiency and threatens the safety of working faces,where irregular coal wall surfaces significantly affect the contact and support effectiveness of the support plate,thereby impacting stability.Through a combination of theoretical analysis,mechanical testing,and numerical simulations,this study establishes a mechanical model of irregular coal wall surfaces to investigate the effects of the undulation period and undulation height on coal wall failure characteristics.This research reveals the mechanical response mechanisms of irregular coal wall surfaces and proposes an innovative method to enhance coal wall stability by improving the supporting cushion material of the support plate,which was validated through numerical simulations.The results show that the undulation height and undulation period significantly influence the macroscopic mechanical parameters of the samples,with the undulation height exerting a more pronounced effect.The strength of the samples with undulating surfaces is approximately 50%-60% that of the samples with flat surfaces.The failure mode under uniaxial compression is predominantly tensile,resulting in long and slender block fragments with a characteristic“Ⅲ”-shaped tensile fracture pattern.During the loading process,samples with undu-lating surfaces dissipate energy at all stages,with a greater proportion of energy dissipation occurring during the early loading stage because of structural damage and the formation of internal cracks.The surface compressive and tensile stresses are correlated with the curvature radius of the convex surface and the elastic modulus of the supporting plate.Reducing the elastic modulus of the supporting plate material can effectively alleviate the stress concentration at convex locations and increase the peak strength.This study provides theoretical foundations and technical references for the prevention and control of coal wall spalling in deep thick coal seam mining.
文摘A theoretical study of the influence of a quasi-electrostatic support on the amplification level of the slow space charge wave(SCW) in the amplification section of a superheterodyne free electron laser(FEL) was carried out. One of the ways to significantly increase the saturation level of the slow SCW is maintaining the conditions of a three-wave parametric resonance between the slow, fast SCWs and the resulting pump electric field. This can be done by introducing the quasielectrostatic support in the superheterodyne FEL amplification section. Also, it was found that the generated pump electric field significantly influences the maintenance of parametric resonance conditions. As a result, this increases the saturation level of the slow SCW by 70%. Finally, the quasi-electrostatic support significantly reduces the maximum value of the electrostatic undulator pump field strength, which is necessary to achieve the maximum saturation level of the slow SCW.
文摘This study evaluates the physical mechanisms of incident waves as they interact with a porous wavy barrier of finite thickness.A wave-trapping chamber is formed between the thick wavy barrier(TWB)and partially reflecting seawall(PRS).The effect of seabed undulations is incorporated into the wave-trapping analysis of the TWB.The boundary value problem proposed in this study is solved using a multidomain boundary element method within the context of linear potential flow theory.Coefficients such as reflection,runup,horizontal force on PRS,and vertical force on TWB are examined for various structural configurations.The position of seabed undulations is analyzed for four scenarios:i)seabed undulations upwave of the wavy barrier with a trapping chamber,ii)seabed undulations upwave of the wavy barrier without a trapping chamber,iii)seabed undulations underneath the wavy barrier with a trapping chamber,and iv)seabed undulations beneath the wavy barrier without a trapping chamber.The study results are compared with known results to verify their accuracy.The effects of PRS,TWB porosity,trapping chamber,plate thickness,seabed type,and submergence depth on hydrodynamic coefficients are analyzed against relative water depth.The study reveals that the introduction of a porous TWB with a trapping chamber results in minimal hydrodynamic coefficients(reduced reflection and force on a wall)compared to a rigid TWB without a trapping chamber.A comparison of various seabeds is reported for all combinations of TWB with a chamber.The sloping seabed upwave of the barrier with a trapping chamber,20%plate porosity,and 50%wall reflection at an appropriate submergence depth could replace gravity-type breakwaters in deeper waters.This study holds great potential for analyzing wave trapping coefficients by TWB to provide an effective coastal protection system.
基金pported by the National Natural Science Foundation of China(Grant Nos.12325409,12388102,12074398,and U2267204)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-060)the Shanghai Pilot Program for Basic Research,Chinese Academy of Sciences Shanghai Branch。
文摘A new on-chip light source configuration has been proposed,which utilizes the interaction between a microwave or laser and a dielectric nanopillar array to generate a periodic electromagnetic near-field and applies periodic transverse acceleration to relativistic electrons to generate high-energy photon radiation.The dielectric nanopillar array interacting with the driving field acts as an electron undulator,in which the near-field drives electrons to oscillate.When an electron beam propagates through this nanopillar array in this light source configuration,it is subjected to a periodic transverse near-field force and will radiate X-ray or evenγ-ray high-energy photons after a relativistic frequency up-conversion.Compared with the undulator which is based on the interaction between strong lasers and nanostructures to generate a plasmonic near-field,this configuration is less prone to damage during operation.
基金supported by the Science and Technology Development Program of Jilin Province,China(No.20160520007JH)the Major Science and Technology Special Project in Jilin Province,China(No.20210301024GX)the National Natural Science Foundation of China(Nos.51601067,51775266,52301169).
文摘The effects of nanostructuring on the mechanical and dry-sliding wear behaviors of a FeCoNi medium-entropy alloy(MEA)were systematically investigated through nano-indentation and ball-on-disc wear tests.The results show that reducing the grain size down into the nano-meter regime,on the one hand,significantly elevates the hardness of the FeCoNi alloy,and on the other hand,facilitates the formation of a surface oxide layer.As a result,the wear rate of the nanocrystalline(NC)FeCoNi alloy is one order of magnitude lower than its coarse-grained counterpart.The NC FeCoNi alloy also exhibits obviously enhanced wear resistance compared with conventional NC Ni and Ni-based alloys in terms of both lower wear rate and friction coefficient.Such enhancement in tribological properties mainly stems from the improved strain hardening ability,owing to the inevitable concentration heterogeneity in MEA that imposes extra resistance to dislocation motion.
基金supported by the National Natural Science Foundation of China(No.E1113R5C10)。
文摘The helical undulator is in high demand in synchrotron radiation facilities for circular polarization generation.Owing to the higher field strength provided by the superconducting undulator compared to the conventional permanent-magnet undulator,greater research efforts should be directed toward this area.The helical superconducting undulator holds great potential in synchrotron radiation facilities,especially in low-energy storage rings that seek circularly polarized radiation with the highest possible radiation flux.Following the successful development of planar superconducting undulators,the Institute of High Energy Physics conducted research and development for the helical superconducting undulator.A 0.5-m-long Deltatype superconducting undulator prototype was developed and tested.Detailed information on the design,fabrication,and cryogenic testing of the prototype is presented and discussed.
文摘Geode, boudinage, and undulation structures are widely distributed in the siliceous beds of the Upper Cretaceous/Tertiary rocks in Jordan. Their formation was attributed to tectonic forces, syngenetic processes, organic disintegration processes, subaquatic gliding, compaction and settlement, and meteoritic impacts. In this work, the structural features in the siliceous beds of Jordan are attributed to an interplay of load and directed pressures, and mineralogical transformation processes (opal-A to opal-CT to quartz), governed by pH changes. Tectonic directed pressure was acting in an ESE-WSW direction and is common in the silicified limestone of Upper Cretaceous.
文摘High-accuracy geoid determination is an essential goal that many groups of scientists and countries are striving to achieve. Techniques for determining geoid models have evolved over time. Unfortunately, this all-important determination requires relatively substantial technical and financial resources, depending on the type of geoid to be determined. This situation justifies the inadequacy, and sometimes absence, of accurate geoid models in many countries, despite the new challenges of altimetric positioning using space or satellite positioning techniques. This study focuses on the establishment of a geometric geoid model using simplistic techniques that are accessible and applicable in restricted or wide areas, with or without gravimetric data. The study was applied to the Dakar-Thiès-Mbour triangle, the two regions in the extreme west of Senegal that are home to the most infrastructure projects with the highest socio-economic stakes, as well as mines currently being exploited, and therefore the highest stakes in terms of positioning. This study also enabled us to assess the accuracy of a number of global field models in Senegal, which are used by some professionals for altimetric positioning using Global Positioning Satellite Systems (GNSS) in the absence of a local geoid model. The estimated geoid model is based on the determination of undulation at various sample points in the study area. To this end, a campaign of GNSS observations and direct levelling was carried out on the various points spread across the study area. These measurements were then used to determine the undulation at each point. Bilinear interpolation was used to deduce the undulations throughout the study area, based on the altimeter conversion grid. This grid was evaluated using GPS/level control points.
文摘ICF(inertial confinement fusion)holds significant potential for achieving controlled nuclear fusion,but challenges related to efficient energy transfer and plasma stabilization remains.This article explores the ion-bubble trigger mechanism as a promising solution for improving the compression and energy deposition processes in ICF,particularly when coupled with external magnetic fields,wigglers,undulators,and trapped magnetic fields.The ion-bubble mechanism enhances energy transfer by creating localized heating in the plasma,increasing the likelihood of fusion ignition.External magnetic fields,through their interaction with plasma particles,can optimize ion-bubble interactions by influencing particle trajectories and stabilizing plasma instabilities.Additionally,wigglers and undulators—devices that create oscillating magnetic fields—offer a means to fine-tune the interaction between plasma and electromagnetic radiation,further enhancing the ion-bubble effect.Trapped magnetic fields,formed through plasma compression,also contribute to plasma confinement and stability,offering further support for the ion-bubble trigger mechanism.By combining these factors,the ion-bubble trigger mechanism in ICF could significantly improve fusion efficiency and bring us closer to realizing sustainable fusion energy.
文摘Brucellosis is an old,infectious and common zoonosis whose causative agents are Gramnegative bacteria from the Brucella genus.Brucellosis is transmitted through direct contactwith infected animals or using unpasteurized dairy products of goats,pigs,camels,sheep,buffalo and cows.Brucellosis is still the most common zoonosis in the world,with mostof cases occurring in developing countries.Today,an approach to traditional medicine andmedicinal plants,especially with regards to the repeated recommendations of the World HealthOrganization,is a necessity.One-third of chemical drugs are produced by using plants andthere is a high potential to produce more drugs from plants.Medicinal plants are helpful inthe management of various conditions,especially bacterial diseases.Although there is notenough scientific evidence regarding the clinical effectiveness of herbal drugs for the treatmentof brucellosis,there is strong evidence on the antimicrobial effects of herbal drugs to preventinfection.Therefore,this article seeks to describe the antibacterial effects of some plantderived essential oils or extracts,so that they can serve as promising choices to develop newanti-Brucella medications,as suitable alternatives to conventional antibiotics for brucellosis,asmuch as possible,taking into account the benefits of these herbal drugs.
文摘Engineering seismic exploration aims at shallow imaging which is confused by statics if the surface is uneven. Direct pre-stack depth migration （DPDM） is based on accurate elevations of sources and receivers, by which static correction is completely abandoned before migration and surely the imaging quality is remarkably improved. To obtain some artificial shot gathers, high-order staggered-grid finite-difference （FD） method is adapted to model acoustic wave propagation. Since the shot gathers are always disturbed by regular interferences, the statics still must be applied to supporting the interference elimination by apparent velocity filtering method. Then all the shot gathers should be removed back to their original positions by reverse statics. Finally, they are migrated by pre-stack reverse-time depth migration and imaged. The numerical experiments show that the DPDM can ideally avoid the mistakes caused by statics and increase imaging precision.
基金funded by a grant from the Deanship for Scientific Research,King Khalid University(Project#GRP-4-1439).
文摘Objective:To investigate the prevalence and risk factors of brucellosis in human and animal’s communities in southern Saudi Arabia.Methods:A cross-sectional sero-epidemiological study was conducted in Aseer and Jazan,Saudi Arabia(October 2017-October 2018).Human serum samples(n=339)were initially screened for Brucella antibodies and positive samples were further titrated for Brucella antibodies by immunocapture assay(titer of≥1:320 as positive).Animal samples(n=828)were screened using the Rose Bengal test.Relationship status was dichotomized to measure and predict independent contributions to variations in human using univariate and multivariate stepwise binary logistic regression model.Results:The rate of brucellosis among the 339 human samples in the two regions was 33.9%,and the rate of acute brucellosis was 12.4%.The rate of brucellosis in animals was 4.7%.Human brucellosis among the target groups was higher in northwestern Aseer(53.3%)compared to Southeastern Aseer(25.9%)and Jazan region(20.6%).The disease was more prevalent among non-Saudi nationals(35.2%)compared to Saudis(30.5%).The rate of brucellosis among butchers and shepherds was 37.5%and 37.2%,respectively.The rate of brucellosis was 37.8%in people over 30 years of age.Our univariate analysis showed that residing in Aseer region(OR:2.60,95%CI:1.50-4.40),especially residing in northwestern Aseer region(OR:4.40,95%CI:2.40-7.90),frequent consumption of raw meat(OR:2.90,95%CI:1.50-5.50),shepherds(OR:2.10,95%CI:0.80-5.30),owning sheep(OR:2.20,95%CI:1.10-4.40),daily contact with animals(OR:2.10,95%CI:0.75-5.80),and those>30-year-old(OR:1.50,95%CI:1.00-2.40)were significantly associated with increased risks of brucellosis.Our multivariate analysis further showed that residing in northwestern Aseer(OR:9.16,95%CI:3.39-24.76)and having sheep(OR:1.16,95%CI:1.00-1.35)were significant and independent risks of brucellosis while residing in agricultural region(OR:0.28,95%CI:0.10-0.78)was a significant and independent protector against brucellosis.Conclusions:The study concluded that residing in northwestern Aseer area and having animals(sheep)are associated with significantly increased risks of brucellosis.
基金supported by China Geological Survey Northeastern Tarim Aeromagnetic and Aerogravity comprehensive survey project(No.12120115039401)
文摘Most of the current computing methods used to determine the magnetic field of a uniformly magnetized cuboid assume that the observation point is located in the upper half space without a source. However, such methods may generate analytical singularities for conditions of undulating terrain. Based on basic geomagnetic field theories, in this study an improved magnetic field expression is derived using an integration method of variable substitution, and all singularity problems for the entire space without a source are discussed and solved. This integration process is simpler than that of previous methods, and final integral results with a more uniform form. AT at all points in the source-flee space can be calculated without requiring coordinate transformation; thus forward modeling is also simplified. Corresponding model tests indicate that the new magnetic field expression is more correct because there is no analytical singularity and can be used with undulating terrain.
基金supported by the National Basic Research Program of China(No.2013CB228602)the National Science and Technology Major Project of China(No.2011ZX05004-003)the National High Tech Research Program of China(No.2013AA064202)
文摘First-break picking is the key step in seismic data processing for surveying undulate surfaces, and directly infl uences the precision of near-surface modeling and effects of static corrections. The current first-break auto-picking methods may fail when the signalto-noise ratio（SNR） is low for seismic data in the undulate area, and require labor and time intensive manual picking. This study develops an improved super-virtual interferometry（SVI） method that combines multichannel and multidomain quality control（MMQC） techniques to achieve auto-picked first breaks. The improved SVI method extends the SVI application to enhance the SNR for near-surface scattered waves for the first time, which allows for the SVI method to adapt to first breaks with complex raypaths by linear combination of refractions and near-surface scattered waves. Methods of inverse and multidomain interferometry are developed to effectively enhance the virtual records extracted by the SVI method. The deconvolution filter for waveforms is used to increase resolution and reduce false picks, while the MMQC technique is designed to auto-correct false picks and increase the stability of auto-picking first breaks. The robust technique developed in this study enables stable processing of large 3D seismic datasets. Higher quality results are obtained using the approach presented in this paper to actual field data from the mountain areas in western China, when compared to some commonly used commercial software.
