The distribution of selected critical elements in the sedimentary rocks of the Carboniferous coal-bearing series within the Polish Coal Basins is presented.Critical elements such as Be,Mg,Si,P,Sc,V,Co,Y,Nb,In,Sb,La,Ce...The distribution of selected critical elements in the sedimentary rocks of the Carboniferous coal-bearing series within the Polish Coal Basins is presented.Critical elements such as Be,Mg,Si,P,Sc,V,Co,Y,Nb,In,Sb,La,Ce,Hf,Ta,W,Bi were analysed using inductively-coupled plasma mass spectrometry(ICP/MS).Concentrations of elements such as Sb,Bi,In and,to a slightly lesser extent,Nb,as well as Sc,show average concentrations higher than those from the upper continental crust.The average concentrations of elements like Hf,Mg,P,Y,La,and Ce are slightly lower than in the upper continental crust.Other elements,such as Be,Co,Si,Ta,W and V have average concentrations that are similar,but slightly enriched or slightly depleted,relative to the upper continental crust.The research showed enrichment of some critical elements in the analysed samples,but not high enough that extraction would be economically viable.Statistical methods,which include correlation coefficients between elements and cluster analysis,reveal a strong positive correlation between elements like Be,Bi,Nb,Sc,Ta,W and V.Very high,almost total,positive correlation is also noted between La and Ce.展开更多
Working toward an efficient duration and timeline for the preconstruction phase should be one of the main objectives for project owners.Failing to plan for and coordinate preconstruction decisions in order to control ...Working toward an efficient duration and timeline for the preconstruction phase should be one of the main objectives for project owners.Failing to plan for and coordinate preconstruction decisions in order to control preconstruction duration and manage time variances can lead to financial insecurities,incomplete contract documents,permitting issues,and unrealistic schedules and resource allocation during this phase.To minimize time variances and ensure a productive decision-making process,project owners should be familiar with critical elements in a project that cause variances in the preconstruction phase timeline.In this study,the impacts of eleven critical preconstruction elements on time variances were analyzed.These eleven preconstruction elements are considered critical in how they impact time variances during the preconstruction phase.They were determined to be critical based either on significantly impacting time variance during the preconstruction phase or believed to be critical from findings from previous studies,however,the findings from this study showed no significant impact on the time variances.In most previous studies focusing on the elements impacting project schedules,data were collected by surveying construction professionals.In this study,objective and quantitative data related to project preconstruction elements were used as opposed to self-reported data.Using the results of this study,project owners and stakeholders will be able to evaluate the critical preconstruction elements impacting the timing of their projects and prioritize decisions related to the critical elements early on during the preconstruction phase.展开更多
This paper aims to present the critical top tension for static equilibrium configurations of a steel catenary riser（SCR） by using the finite element method. The critical top tension is the minimum top tension that c...This paper aims to present the critical top tension for static equilibrium configurations of a steel catenary riser（SCR） by using the finite element method. The critical top tension is the minimum top tension that can maintain the equilibrium of the SCR. If the top tension is smaller than the critical value, the equilibrium of the SCR does not exist. If the top tension is larger than the critical value, there are two possible equilibrium configurations. These two configurations exhibit the nonlinear large displacement. The configuration with the smaller displacement is stable, while the one with larger displacement is unstable. The numerical results show that the increases in the riser＇s vertical distances, horizontal offsets, riser＇s weights, internal flow velocities, and current velocities increase the critical top tensions of the SCR. In addition, the parametric studies are also performed in order to investigate the limit states for the analysis and design of the SCR.展开更多
The Middle Pennsylvanian,Langsettian sub-stage Clintwood coal,along with its correlatives,was one of the more important energy resources in eastern Kentucky.The coal thickens from the NE-SW-trending Belfry anticline i...The Middle Pennsylvanian,Langsettian sub-stage Clintwood coal,along with its correlatives,was one of the more important energy resources in eastern Kentucky.The coal thickens from the NE-SW-trending Belfry anticline in central Pike County to the southeast,towards the Virginia-Kentucky border.Much of the thickness increase is in the bright lithotypes below a dull lithology.The bright lithologies transition from a bright clarain+vitrain+fusain lithology to a clarain+fusain lithology to the southeast.Half of the lithotypes in the three analyzed sections exceed 1000-μg/g Rare earth elements+Y+Sc(REYSc)(ash basis).The La_(N)/Sm_(N)vs.Gd_(N)/Yb_(N)and La_(N)/Sm_(N)vs.Ce_(N)/Ce_(N)^(*)plots suggest that the top lithotype may have had best indication of an oxidizing environment.Positive Gd_(N)/Gd_(N)^(*)and EuN/EuN*in some of the lithologies suggests that there may have been a hydrothermal influence in the sediment sources and/or in the diagenesis of the coal.Consideration of La_(N)/Sm_(N)and Zr(μg/g;ash basis),Zr vs.Sr,and V/Cr vs.inertinite/(inertinite+vitrinite)indicates that the dull lithotypes existed in a distinct geochemical environment compared to the brighter lithotypes.The isolation of the dull lithotypes from the bright lithotypes is supported by principal components analysis on inertinite/(inertinite+vitrinite),LaN/SmN,V/Cr,Sr,and either Zr or Ln(100(TiO_(2))/Al_(2)O_(3)).展开更多
The increasing use of tellurium(Te) in electronics and renewable energy technologies has elevated its environmental concentration,posing ecological and health risks.This study addresses the critical need for effective...The increasing use of tellurium(Te) in electronics and renewable energy technologies has elevated its environmental concentration,posing ecological and health risks.This study addresses the critical need for effective methods to speciate Te by focusing on its two primary redox states—tellurite(Te(Ⅳ)) and tellurate(Te(Ⅵ))—which differ in reactivity,mobility,and toxicity.Existing analytical methods for Te speciation are often limited in sensitivity and can't simultaneously determine both species.In response,we present a novel,rapid,practical,and highly sensitive approach for determining Te(Ⅳ) and Te(Ⅵ) using frontal chromatography coupled with inductively coupled plasma mass spectrometry(FC-ICP-MS).Multivariate optimization of chromatographic conditions,along with the exploitation of the "carbon effect" and careful isotope selection,yield detection limits of 1.0 ng/L for Te(Ⅳ) and 1.3 ng/L for Te(Ⅵ) with a total analysis time of five minutes.Acidification with nitric acid is the only sample pretreatment required.Applied to natural waters,sediments,and soils,the method demonstrates high accuracy,superior sensitivity,greenness,and practicality,compared to state-of-the-art methodologies,offering an alternative and advantageous solution for routine Te speciation analysis across various environmental compartments.展开更多
This paper shows that for DEM simulations of triaxial tests using samples with a grading that is repre- sentative of a real soil, the sample size significantly influences the observed material response. Four DEM sampl...This paper shows that for DEM simulations of triaxial tests using samples with a grading that is repre- sentative of a real soil, the sample size significantly influences the observed material response. Four DEM samples with identical initial states were produced： three cylindrical samples bounded by rigid wails and one bounded by a cubical periodic cell, When subjected to triaxial loading, the samples with rigid boundaries were more dilative, stiffer and reached a higher peak stress ratio than the sample enclosed by periodic boundaries. For the rigid-wall samples, dilatancy increased and stiffness decreased with increasing sample size, The periodic sample was effectively homogeneous, The void ratio increased and the contact density decreased close to the rigid walls, This heterogeneity reduced with increasing sample size. The positions of the critical state lines （CSLs） of the overall response in e-log p＇ space were sensitive to the sample size, although no difference was observed between their slopes. The critical states of the interior regions of the rigid-wall-bounded samples approached that of the homogeneous periodic sample with increasing sample size. The ultimate strength of the material at the critical state is independent of sample size.展开更多
文摘The distribution of selected critical elements in the sedimentary rocks of the Carboniferous coal-bearing series within the Polish Coal Basins is presented.Critical elements such as Be,Mg,Si,P,Sc,V,Co,Y,Nb,In,Sb,La,Ce,Hf,Ta,W,Bi were analysed using inductively-coupled plasma mass spectrometry(ICP/MS).Concentrations of elements such as Sb,Bi,In and,to a slightly lesser extent,Nb,as well as Sc,show average concentrations higher than those from the upper continental crust.The average concentrations of elements like Hf,Mg,P,Y,La,and Ce are slightly lower than in the upper continental crust.Other elements,such as Be,Co,Si,Ta,W and V have average concentrations that are similar,but slightly enriched or slightly depleted,relative to the upper continental crust.The research showed enrichment of some critical elements in the analysed samples,but not high enough that extraction would be economically viable.Statistical methods,which include correlation coefficients between elements and cluster analysis,reveal a strong positive correlation between elements like Be,Bi,Nb,Sc,Ta,W and V.Very high,almost total,positive correlation is also noted between La and Ce.
文摘Working toward an efficient duration and timeline for the preconstruction phase should be one of the main objectives for project owners.Failing to plan for and coordinate preconstruction decisions in order to control preconstruction duration and manage time variances can lead to financial insecurities,incomplete contract documents,permitting issues,and unrealistic schedules and resource allocation during this phase.To minimize time variances and ensure a productive decision-making process,project owners should be familiar with critical elements in a project that cause variances in the preconstruction phase timeline.In this study,the impacts of eleven critical preconstruction elements on time variances were analyzed.These eleven preconstruction elements are considered critical in how they impact time variances during the preconstruction phase.They were determined to be critical based either on significantly impacting time variance during the preconstruction phase or believed to be critical from findings from previous studies,however,the findings from this study showed no significant impact on the time variances.In most previous studies focusing on the elements impacting project schedules,data were collected by surveying construction professionals.In this study,objective and quantitative data related to project preconstruction elements were used as opposed to self-reported data.Using the results of this study,project owners and stakeholders will be able to evaluate the critical preconstruction elements impacting the timing of their projects and prioritize decisions related to the critical elements early on during the preconstruction phase.
基金supported by the Thailand Research Fund(TRF)through the Royal Golden Jubilee Ph.D.Program(Grant No.PHD/0112/2553)the National Research University(NRU)initiative
文摘This paper aims to present the critical top tension for static equilibrium configurations of a steel catenary riser（SCR） by using the finite element method. The critical top tension is the minimum top tension that can maintain the equilibrium of the SCR. If the top tension is smaller than the critical value, the equilibrium of the SCR does not exist. If the top tension is larger than the critical value, there are two possible equilibrium configurations. These two configurations exhibit the nonlinear large displacement. The configuration with the smaller displacement is stable, while the one with larger displacement is unstable. The numerical results show that the increases in the riser＇s vertical distances, horizontal offsets, riser＇s weights, internal flow velocities, and current velocities increase the critical top tensions of the SCR. In addition, the parametric studies are also performed in order to investigate the limit states for the analysis and design of the SCR.
文摘The Middle Pennsylvanian,Langsettian sub-stage Clintwood coal,along with its correlatives,was one of the more important energy resources in eastern Kentucky.The coal thickens from the NE-SW-trending Belfry anticline in central Pike County to the southeast,towards the Virginia-Kentucky border.Much of the thickness increase is in the bright lithotypes below a dull lithology.The bright lithologies transition from a bright clarain+vitrain+fusain lithology to a clarain+fusain lithology to the southeast.Half of the lithotypes in the three analyzed sections exceed 1000-μg/g Rare earth elements+Y+Sc(REYSc)(ash basis).The La_(N)/Sm_(N)vs.Gd_(N)/Yb_(N)and La_(N)/Sm_(N)vs.Ce_(N)/Ce_(N)^(*)plots suggest that the top lithotype may have had best indication of an oxidizing environment.Positive Gd_(N)/Gd_(N)^(*)and EuN/EuN*in some of the lithologies suggests that there may have been a hydrothermal influence in the sediment sources and/or in the diagenesis of the coal.Consideration of La_(N)/Sm_(N)and Zr(μg/g;ash basis),Zr vs.Sr,and V/Cr vs.inertinite/(inertinite+vitrinite)indicates that the dull lithotypes existed in a distinct geochemical environment compared to the brighter lithotypes.The isolation of the dull lithotypes from the bright lithotypes is supported by principal components analysis on inertinite/(inertinite+vitrinite),LaN/SmN,V/Cr,Sr,and either Zr or Ln(100(TiO_(2))/Al_(2)O_(3)).
基金Open access funding provided by Universitàdegli Studi dell'Insubria within the CRUI-CARE Agreement。
文摘The increasing use of tellurium(Te) in electronics and renewable energy technologies has elevated its environmental concentration,posing ecological and health risks.This study addresses the critical need for effective methods to speciate Te by focusing on its two primary redox states—tellurite(Te(Ⅳ)) and tellurate(Te(Ⅵ))—which differ in reactivity,mobility,and toxicity.Existing analytical methods for Te speciation are often limited in sensitivity and can't simultaneously determine both species.In response,we present a novel,rapid,practical,and highly sensitive approach for determining Te(Ⅳ) and Te(Ⅵ) using frontal chromatography coupled with inductively coupled plasma mass spectrometry(FC-ICP-MS).Multivariate optimization of chromatographic conditions,along with the exploitation of the "carbon effect" and careful isotope selection,yield detection limits of 1.0 ng/L for Te(Ⅳ) and 1.3 ng/L for Te(Ⅵ) with a total analysis time of five minutes.Acidification with nitric acid is the only sample pretreatment required.Applied to natural waters,sediments,and soils,the method demonstrates high accuracy,superior sensitivity,greenness,and practicality,compared to state-of-the-art methodologies,offering an alternative and advantageous solution for routine Te speciation analysis across various environmental compartments.
基金funding from the Royal Commission for the Exhibition of 1851provided as part of grant EP/1006761/1 from the Engineering and Physical Sciences Research Council
文摘This paper shows that for DEM simulations of triaxial tests using samples with a grading that is repre- sentative of a real soil, the sample size significantly influences the observed material response. Four DEM samples with identical initial states were produced： three cylindrical samples bounded by rigid wails and one bounded by a cubical periodic cell, When subjected to triaxial loading, the samples with rigid boundaries were more dilative, stiffer and reached a higher peak stress ratio than the sample enclosed by periodic boundaries. For the rigid-wall samples, dilatancy increased and stiffness decreased with increasing sample size, The periodic sample was effectively homogeneous, The void ratio increased and the contact density decreased close to the rigid walls, This heterogeneity reduced with increasing sample size. The positions of the critical state lines （CSLs） of the overall response in e-log p＇ space were sensitive to the sample size, although no difference was observed between their slopes. The critical states of the interior regions of the rigid-wall-bounded samples approached that of the homogeneous periodic sample with increasing sample size. The ultimate strength of the material at the critical state is independent of sample size.
