Traditional taxonomic sorting of samples into recognizable taxonomic units, such as morphospecies or morphotypes, is commonly relied upon in conservation biology and ethnobiological studies. However, understanding the...Traditional taxonomic sorting of samples into recognizable taxonomic units, such as morphospecies or morphotypes, is commonly relied upon in conservation biology and ethnobiological studies. However, understanding the criteria used for traditional nomenclature of fungi, particularly wild edible mushrooms across linguistic groups, remains limited, leading to frequent errors in species recognition. This study seeks to assess how linguistic affiliations influence the local naming of useful wild mushrooms, and is the first of its kind in Benin. In order to understand how local people recognize, classify and name mushrooms that develop in or close to their villages, 2234 respondents from five socio-linguistic groups across three geographical areas were interviewed. Structured and semi-structured interviews were conducted to gather data on the local naming criteria for edible wild mushrooms. Citation scores were recorded for both nomenclature criteria and species, considering variables such as linguistic groups, age, and language. Twenty-two nomenclature criteria were used by local people to name edible wild species. Strong similarity in classification and naming of species was shown in 97% of the languages, while 3% showed differing classification criteria. The Gur, Atlantic, and Mande linguistic groups demonstrated more comprehensive traditional taxonomic and nomenclatural knowledge, sharing six common criteria: texture, taste, size, kingdom (Fungi), form, and substrate. Overall, local populations possess extensive knowledge regarding the diversity of wild edible mushrooms in their environment.展开更多
Based on an analysis of 280 Type SNIa supernovae and gamma-ray bursts redshifts in the range of z = 0.0104 - 8.1 the Hubble diagram is shown to follow a strictly exponential slope predicting an exponentially expanding...Based on an analysis of 280 Type SNIa supernovae and gamma-ray bursts redshifts in the range of z = 0.0104 - 8.1 the Hubble diagram is shown to follow a strictly exponential slope predicting an exponentially expanding or static universe. At redshifts > 2 - 3 ΛCDM models show a poor agreement with the observed data. Based on the results presented in this paper, the Hubble diagram test does not necessarily support the idea of expansion according to the big-bang concordance model.展开更多
In this letter,the streamer propagation in the atmospheric pressure helium plasma jet with afloating electrode nozzle driven by the kHz AC power supply is investigated.The current signal induced by the space charges a...In this letter,the streamer propagation in the atmospheric pressure helium plasma jet with afloating electrode nozzle driven by the kHz AC power supply is investigated.The current signal induced by the space charges and the mean propagation velocity of the guided ionization waves are measured by the capacitive probe method in the discharge region.The space charges in the guided ionization waves are found to increase with the applied voltage,which enhances both the electric field near the streamer head and the propagation velocity.The applicability of the streamer mechanism to the propagation of the guided ionization waves is validated by this electrical diagnostic method.展开更多
This study presents results from sentiment analysis of Dynamic message sign (DMS) message content, focusing on messages that include numbers of road fatalities. As a traffic management tool, DMS plays a role in influe...This study presents results from sentiment analysis of Dynamic message sign (DMS) message content, focusing on messages that include numbers of road fatalities. As a traffic management tool, DMS plays a role in influencing driver behavior and assisting transportation agencies in achieving safe and efficient traffic movement. However, the psychological and behavioral effects of displaying fatality numbers on DMS remain poorly understood;hence, it is important to know the potential impacts of displaying such messages. The Iowa Department of Transportation displays the number of fatalities on a first screen, followed by a supplemental message hoping to promote safe driving;an example is “19 TRAFFIC DEATHS THIS YEAR IF YOU HAVE A SUPER BOWL DON’T DRIVE HIGH.” We employ natural language processing to decode the sentiment and undertone of the supplementary message and investigate how they influence driving speeds. According to the results of a mixed effect model, drivers reduced speeds marginally upon encountering DMS fatality text with a positive sentiment with a neutral undertone. This category had the largest associated amount of speed reduction, while messages with negative sentiment with a negative undertone had the second largest amount of speed reduction, greater than other combinations, including positive sentiment with a positive undertone.展开更多
To improve the power consumption of parallel applications at the runtime, modern processors provide frequency scaling and power limiting capabilities. In this work, a runtime strategy is proposed to maximize performan...To improve the power consumption of parallel applications at the runtime, modern processors provide frequency scaling and power limiting capabilities. In this work, a runtime strategy is proposed to maximize performance under a given power budget by distributing the available power according to the relative GPU utilization. Time series forecasting methods were used to develop workload prediction models that provide accurate prediction of GPU utilization during application execution. Experiments were performed on a multi-GPU computing platform DGX-1 equipped with eight NVIDIA V100 GPUs used for quantum chemistry calculations in the GAMESS package. For a limited power budget, the proposed strategy may deliver as much as hundred times better GAMESS performance than that obtained when the power is distributed equally among all the GPUs.展开更多
Waterlogged soils and submerged sediments in wetlands and agricultural lands used for rice paddies and aquaculture have anaerobic conditions that slow and prevent the photo and microbial degradation of dioxin TCDD (2,...Waterlogged soils and submerged sediments in wetlands and agricultural lands used for rice paddies and aquaculture have anaerobic conditions that slow and prevent the photo and microbial degradation of dioxin TCDD (2,3,7,8-tetracholorodibenzo-p-dioxin), enabling it to persist in environments for long periods. Over 1.6 million ha of land in southern Vietnam were sprayed with 2,4,5-T herbicides (e.g. Agent Orange) contaminated with dioxin TCDD during the Vietnam War (1961-1971);45% of these ha received four or more spray flight missions. Dioxins are endocrine disrupters and may induce cardiovascular disease, growth, and developmental defects, diabetes, hormonal dysfunctions and disruptions, certain cancers, and chloracne. Outpatient screening clinic 2020 data on Vietnamese children suspected of congenital heart disease (CHD) showed the childhood CHD prevalence rate in Vietnam of 13.356/1000, significantly elevated compared to the Asian CHD prevalence rate of 3.531/1000. CHD prevalence rate differences between North Vietnam (2.541/1000) and south of the 17<sup>th</sup> parallel (10.809/1000) were significant. Vietnamese farmers, especially pregnant women whose occupations involve daily contact with soil and sediments where dioxin TCDD persists in the environment may be at risk of dioxin accumulation from dermal exposure and bioaccumulation via diet. There is an urgent need for funded longitudinal genetic and clinical studies to assess CHD and other organ system childhood malformations due to in utero TCDD exposure. We recommend an integrated research design involving 1) site-specific locations that received high volumes and multiple spray loads of herbicides during the Vietnam War;2) soil sampling of submerged and waterlogged soils and sediments where TCDD may not have degraded;3) production areas of agriculture, fisheries, and other aquatic products;4) risk assessment dioxin levels in foods where TCDD is likely to bioaccumulate;5) child-bearing age and pregnant women with potentially high sensitivity to long-term low dose exposure, and 6) men and women in occupations that are in daily contact with contaminated soil and sediments as part of their job routines.展开更多
A greenhouse experiment was conducted involving complete/intact 100 cm cores of a fragipan soil. The cores were maintained in moist conditions throughout the experiment as annual ryegrass (Lolium multiflorum) or festu...A greenhouse experiment was conducted involving complete/intact 100 cm cores of a fragipan soil. The cores were maintained in moist conditions throughout the experiment as annual ryegrass (Lolium multiflorum) or festulolium (Lolium spp and Fescue spp hybrid) were grown with and without additional surface applied amendments, including NaF, NaNO3, NaCl, and KCl. The results suggest a significant effect of annual ryegrass and festulolium on fragipan horizon degradation after 24 months. Annual ryegrass and festulolium were found to effectively change the structure of the fragipan horizon when planted on the soil surface and roots grew through the upper soil profile and penetrated into the fragipan. The fragipan structural change (degradation) appeared to increase with each planting sequence, particularly with soybean crop rotations. Sodium nitrate added to the soil surface with the growth of annual ryegrass resulted in a significant synergistic effect for degrading the fragipan horizon. The other amendments were not as effective in causing additional fragipan degradation.展开更多
In the U.S. biofuel industry is using corn (<em>Zea mays</em> L.) residue mix (CRM) consisting of corncob and stover for cellulosic ethanol and biogas production. The field storage method left different de...In the U.S. biofuel industry is using corn (<em>Zea mays</em> L.) residue mix (CRM) consisting of corncob and stover for cellulosic ethanol and biogas production. The field storage method left different depths of CRM on the field after its removal, where negative effects on plant growth were observed. The objective of this study is to evaluate the CRM effect on selected soil health indicators. The field study conducted with four different depths of CRM, two tillage systems (no-till (NT) and chisel plow (CP), and three nitrogen (N) rates (0, 180, and 270 kg<span style="white-space:nowrap;">⋅</span>N<span style="white-space:nowrap;">⋅</span>ha<sup><span style="white-space:nowrap;">−</span>1</sup>) in a randomized complete block design with split-split arrangements in three replications in a continuous corn system from 2010 to 2012 at the Agronomy Research Farm at Iowa State University. The findings of this study showed a negative effect on soil organic carbon (SOC) change across all treatments at 0 - 15 cm (<span style="white-space:nowrap;">−</span>0.35 to <span style="white-space:nowrap;">−</span>0.03 <span style="white-space:nowrap;">Mg⋅ha<sup>−1</sup>⋅yr<sup>−1</sup></span>), while at 15 - 30 cm there was an increase in SOC rate (0.13 to 0.40 Mg<span style="white-space:nowrap;">⋅</span>ha<sup><span style="white-space:nowrap;">−</span>1</sup><span style="white-space:nowrap;">⋅</span>yr<sup><span style="white-space:nowrap;">−</span>1</sup>) after 2-yr. In addition, soil aggregate-associated C of macro-aggregates decreased by 8%, while micro-aggregates increased by 2%. Soil microbial biomass carbon (MBC) across tillage and N rates for 2.5 & 7.5 CRM treatments increased by 14% in June to July 2011, while in 2012 increased by 9%. However, at the 15 cm soil depth, soil bulk density (<em>ρ</em><sub>b</sub>), soil penetration resistance (SPR), and soil pH showed no significant differences among CRM treatments. The findings of this study showed that in-field CRM management can affect certain soil health parameters in the short term.展开更多
The effects of mass concentration and injection pressure on the atomization characteristics of low-viscosity fuel spray are studied in a constant-volume chamber.Microscopic spray parameters are measured by laser diffr...The effects of mass concentration and injection pressure on the atomization characteristics of low-viscosity fuel spray are studied in a constant-volume chamber.Microscopic spray parameters are measured by laser diffraction at different axial and radial positions downstream of the nozzle.The results show that the atomization effect is inhibited linearly with the increase of mass concentration.The increase of injection pressure promotes the droplet breakup.However,the trend gradually weakens and becomes more noticeable at high concentrations.Comparing with the concentration,the influence of the injection pressure on the atomization characteristics is dominant.Although low concentration and high injection pressure can promote the droplet breakup,they also increase the probability of droplet collision,resulting in droplet aggregation.This is more evident in low-viscosity fuels.The droplet size increases in the axial direction owing to the aggregation.However,the diameter decreases in the radial direction owing to the outward deflection of small droplets caused by air turbulence and entrainment.In addition,the high-velocity airflow significantly promotes the droplet breakup near the nozzle and spray axis regions and inhibits the aggregation effect.However,the lower-viscosity fuels keep smaller droplet sizes and better atomization in the whole spraying process,which is easier to realize than the higher-viscosity fuels.Overall,low concentration,high injection pressure,and low viscosity of fuel have beneficial effects on the droplet breakup.This is very important for improving the atomization effect of fuel.展开更多
As a requisite to determining management practice effects on stored soil organic carbon (SOC) stock in a landscape unit, the baseline SOC stock with depth must be determined and the land use, management practices and ...As a requisite to determining management practice effects on stored soil organic carbon (SOC) stock in a landscape unit, the baseline SOC stock with depth must be determined and the land use, management practices and erosion-induced changes measured periodically or over a period of time. The SOC loss and additions due to soil erosion, transport and deposition must be accounted for or be quantified when determining the real impact of the management practices on net SOC stock over time. Quantifying the SOC loss due to erosion will help avoid over estimation of the management practice performances. Appropriate soil sampling designs and sampling procedures are needed to establish a SOC stock baseline and to monitor and verify new SOC storage or sequestration as a result of a management practice. The Dinesen Prairie landscape in western Iowa, USA was sampled to provide a SOC stock baseline and then the adjacent cropland was sampled to determine the past impact of land use change, management practices and erosion on SOC stock retention. After 100 to 150 years of farming, the entire cropland landscape retained only 49% of the baseline prairie SOC stock. Only the cropland toe-slope (TS) retained more SOC stock than the prairie TS as a result of the erosion, transport and deposition of SOC rich sediment on the TS.展开更多
An explicitly coupled two-dimensional (2D) multiphysics finite element method (FEM) framework comprised of thermal, phase field, mechanical and electromagnetic (TPME) equations was developed to simulate the conversion...An explicitly coupled two-dimensional (2D) multiphysics finite element method (FEM) framework comprised of thermal, phase field, mechanical and electromagnetic (TPME) equations was developed to simulate the conversion of solid kerogen in oil shale to liquid oil through </span><i><span style="font-family:Verdana;font-size:12px;">in-situ</span></i><span style="font-family:Verdana;font-size:12px;"> pyrolysis by radio frequency heating. Radio frequency heating as a method of <i></span><i><span style="font-family:Verdana;font-size:12px;">in-situ</span></i><span style="font-family:Verdana;font-size:12px;"></i> pyrolysis represents a tenable enhanced oil recovery method, whereby an applied electrical potential difference across a target oil shale formation is converted to thermal energy, heating the oil shale and causing it to liquify to become liquid oil. A number of <i></span><i><span style="font-family:Verdana;font-size:12px;">in-situ</span></i><span style="font-family:Verdana;font-size:12px;"></i> pyrolysis methods are reviewed but the focus of this work is on the verification of the TPME numerical framework to model radio frequency heating as a potential dielectric heating process for enhanced oil recovery.</span></span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">Very few studies exist which describe production from oil shale;furthermore, there are none that specifically address the verification of numerical models describing radio frequency heating. As a result, the Method of Manufactured Solutions (MMS) was used as an analytical verification method of the developed numerical code. Results show that the multiphysics finite element framework was adequately modeled enabling the simulation of kerogen conversion to oil as a part of the analysis of a TPME numerical model.展开更多
The effect of UV- and 137Cs gamma radiation on the structural and chemical integrity of human hair was studied to determine the feasibility of using human hair as a non-invasive biomarker of radiation exposure to ioni...The effect of UV- and 137Cs gamma radiation on the structural and chemical integrity of human hair was studied to determine the feasibility of using human hair as a non-invasive biomarker of radiation exposure to ionized gamma- and non-ionized UV-radiation. Steady state tryptophan (Trp) fluorescence and chemical analytical methods were used to evaluate the molecular integrity of Trp fluorophores and SH-groups in hair proteins and to assess the radiation induced damage quantitatively. It was found that human hair fibers were progressively damaged by exposure to both UV- and ionized gamma radiation. Damage to the hair was evidenced by a decrease in the fluorescence intensity as a result of observed depletion of the amino acid tryptophan as well as significant reduction in a number of free SH-groups in hair proteins. Hair damage was dose-dependent for exposures between 0 and 10.0 Gy and 0 - 20 J/cm2 of UV-radiation. Additional results demonstrate that hair-fibers exposed to gamma rays, with much higher quantum energy than UV, undergo a smaller extent of changes in Trp fluorescence than when exposed to lower or equal energy of UV-irradiation. The stable Trp fluorophore appears to be extremely sensitive to UV-radiation in contrast to the ionized gamma radiation whose damage is originated from the reaction of free radicals and direct deposition of energy. We conclude that fluorescence spectroscopy represents a useful tool in the quantitative evaluation of the radiation exposure and could also be used for the rapid and non-invasive assessment of radiation dose i.e. biodosimeter. The approach is simple, non-invasive and appears to have considerable potential that enables quantitative evaluation of radiation dose exposure in a single hair fiber.展开更多
文摘Traditional taxonomic sorting of samples into recognizable taxonomic units, such as morphospecies or morphotypes, is commonly relied upon in conservation biology and ethnobiological studies. However, understanding the criteria used for traditional nomenclature of fungi, particularly wild edible mushrooms across linguistic groups, remains limited, leading to frequent errors in species recognition. This study seeks to assess how linguistic affiliations influence the local naming of useful wild mushrooms, and is the first of its kind in Benin. In order to understand how local people recognize, classify and name mushrooms that develop in or close to their villages, 2234 respondents from five socio-linguistic groups across three geographical areas were interviewed. Structured and semi-structured interviews were conducted to gather data on the local naming criteria for edible wild mushrooms. Citation scores were recorded for both nomenclature criteria and species, considering variables such as linguistic groups, age, and language. Twenty-two nomenclature criteria were used by local people to name edible wild species. Strong similarity in classification and naming of species was shown in 97% of the languages, while 3% showed differing classification criteria. The Gur, Atlantic, and Mande linguistic groups demonstrated more comprehensive traditional taxonomic and nomenclatural knowledge, sharing six common criteria: texture, taste, size, kingdom (Fungi), form, and substrate. Overall, local populations possess extensive knowledge regarding the diversity of wild edible mushrooms in their environment.
文摘Based on an analysis of 280 Type SNIa supernovae and gamma-ray bursts redshifts in the range of z = 0.0104 - 8.1 the Hubble diagram is shown to follow a strictly exponential slope predicting an exponentially expanding or static universe. At redshifts > 2 - 3 ΛCDM models show a poor agreement with the observed data. Based on the results presented in this paper, the Hubble diagram test does not necessarily support the idea of expansion according to the big-bang concordance model.
基金supported by National Natural Science Foundation of China(Nos.10775087 and51907190)the State Key Laboratory of NBC Protection for Civilian(SKLNBC 2019–16)。
文摘In this letter,the streamer propagation in the atmospheric pressure helium plasma jet with afloating electrode nozzle driven by the kHz AC power supply is investigated.The current signal induced by the space charges and the mean propagation velocity of the guided ionization waves are measured by the capacitive probe method in the discharge region.The space charges in the guided ionization waves are found to increase with the applied voltage,which enhances both the electric field near the streamer head and the propagation velocity.The applicability of the streamer mechanism to the propagation of the guided ionization waves is validated by this electrical diagnostic method.
文摘This study presents results from sentiment analysis of Dynamic message sign (DMS) message content, focusing on messages that include numbers of road fatalities. As a traffic management tool, DMS plays a role in influencing driver behavior and assisting transportation agencies in achieving safe and efficient traffic movement. However, the psychological and behavioral effects of displaying fatality numbers on DMS remain poorly understood;hence, it is important to know the potential impacts of displaying such messages. The Iowa Department of Transportation displays the number of fatalities on a first screen, followed by a supplemental message hoping to promote safe driving;an example is “19 TRAFFIC DEATHS THIS YEAR IF YOU HAVE A SUPER BOWL DON’T DRIVE HIGH.” We employ natural language processing to decode the sentiment and undertone of the supplementary message and investigate how they influence driving speeds. According to the results of a mixed effect model, drivers reduced speeds marginally upon encountering DMS fatality text with a positive sentiment with a neutral undertone. This category had the largest associated amount of speed reduction, while messages with negative sentiment with a negative undertone had the second largest amount of speed reduction, greater than other combinations, including positive sentiment with a positive undertone.
文摘To improve the power consumption of parallel applications at the runtime, modern processors provide frequency scaling and power limiting capabilities. In this work, a runtime strategy is proposed to maximize performance under a given power budget by distributing the available power according to the relative GPU utilization. Time series forecasting methods were used to develop workload prediction models that provide accurate prediction of GPU utilization during application execution. Experiments were performed on a multi-GPU computing platform DGX-1 equipped with eight NVIDIA V100 GPUs used for quantum chemistry calculations in the GAMESS package. For a limited power budget, the proposed strategy may deliver as much as hundred times better GAMESS performance than that obtained when the power is distributed equally among all the GPUs.
文摘Waterlogged soils and submerged sediments in wetlands and agricultural lands used for rice paddies and aquaculture have anaerobic conditions that slow and prevent the photo and microbial degradation of dioxin TCDD (2,3,7,8-tetracholorodibenzo-p-dioxin), enabling it to persist in environments for long periods. Over 1.6 million ha of land in southern Vietnam were sprayed with 2,4,5-T herbicides (e.g. Agent Orange) contaminated with dioxin TCDD during the Vietnam War (1961-1971);45% of these ha received four or more spray flight missions. Dioxins are endocrine disrupters and may induce cardiovascular disease, growth, and developmental defects, diabetes, hormonal dysfunctions and disruptions, certain cancers, and chloracne. Outpatient screening clinic 2020 data on Vietnamese children suspected of congenital heart disease (CHD) showed the childhood CHD prevalence rate in Vietnam of 13.356/1000, significantly elevated compared to the Asian CHD prevalence rate of 3.531/1000. CHD prevalence rate differences between North Vietnam (2.541/1000) and south of the 17<sup>th</sup> parallel (10.809/1000) were significant. Vietnamese farmers, especially pregnant women whose occupations involve daily contact with soil and sediments where dioxin TCDD persists in the environment may be at risk of dioxin accumulation from dermal exposure and bioaccumulation via diet. There is an urgent need for funded longitudinal genetic and clinical studies to assess CHD and other organ system childhood malformations due to in utero TCDD exposure. We recommend an integrated research design involving 1) site-specific locations that received high volumes and multiple spray loads of herbicides during the Vietnam War;2) soil sampling of submerged and waterlogged soils and sediments where TCDD may not have degraded;3) production areas of agriculture, fisheries, and other aquatic products;4) risk assessment dioxin levels in foods where TCDD is likely to bioaccumulate;5) child-bearing age and pregnant women with potentially high sensitivity to long-term low dose exposure, and 6) men and women in occupations that are in daily contact with contaminated soil and sediments as part of their job routines.
文摘A greenhouse experiment was conducted involving complete/intact 100 cm cores of a fragipan soil. The cores were maintained in moist conditions throughout the experiment as annual ryegrass (Lolium multiflorum) or festulolium (Lolium spp and Fescue spp hybrid) were grown with and without additional surface applied amendments, including NaF, NaNO3, NaCl, and KCl. The results suggest a significant effect of annual ryegrass and festulolium on fragipan horizon degradation after 24 months. Annual ryegrass and festulolium were found to effectively change the structure of the fragipan horizon when planted on the soil surface and roots grew through the upper soil profile and penetrated into the fragipan. The fragipan structural change (degradation) appeared to increase with each planting sequence, particularly with soybean crop rotations. Sodium nitrate added to the soil surface with the growth of annual ryegrass resulted in a significant synergistic effect for degrading the fragipan horizon. The other amendments were not as effective in causing additional fragipan degradation.
文摘In the U.S. biofuel industry is using corn (<em>Zea mays</em> L.) residue mix (CRM) consisting of corncob and stover for cellulosic ethanol and biogas production. The field storage method left different depths of CRM on the field after its removal, where negative effects on plant growth were observed. The objective of this study is to evaluate the CRM effect on selected soil health indicators. The field study conducted with four different depths of CRM, two tillage systems (no-till (NT) and chisel plow (CP), and three nitrogen (N) rates (0, 180, and 270 kg<span style="white-space:nowrap;">⋅</span>N<span style="white-space:nowrap;">⋅</span>ha<sup><span style="white-space:nowrap;">−</span>1</sup>) in a randomized complete block design with split-split arrangements in three replications in a continuous corn system from 2010 to 2012 at the Agronomy Research Farm at Iowa State University. The findings of this study showed a negative effect on soil organic carbon (SOC) change across all treatments at 0 - 15 cm (<span style="white-space:nowrap;">−</span>0.35 to <span style="white-space:nowrap;">−</span>0.03 <span style="white-space:nowrap;">Mg⋅ha<sup>−1</sup>⋅yr<sup>−1</sup></span>), while at 15 - 30 cm there was an increase in SOC rate (0.13 to 0.40 Mg<span style="white-space:nowrap;">⋅</span>ha<sup><span style="white-space:nowrap;">−</span>1</sup><span style="white-space:nowrap;">⋅</span>yr<sup><span style="white-space:nowrap;">−</span>1</sup>) after 2-yr. In addition, soil aggregate-associated C of macro-aggregates decreased by 8%, while micro-aggregates increased by 2%. Soil microbial biomass carbon (MBC) across tillage and N rates for 2.5 & 7.5 CRM treatments increased by 14% in June to July 2011, while in 2012 increased by 9%. However, at the 15 cm soil depth, soil bulk density (<em>ρ</em><sub>b</sub>), soil penetration resistance (SPR), and soil pH showed no significant differences among CRM treatments. The findings of this study showed that in-field CRM management can affect certain soil health parameters in the short term.
基金Project supported by the Young Scientists Fund of National Natural Science Foundation of China(Grant No.11802136).
文摘The effects of mass concentration and injection pressure on the atomization characteristics of low-viscosity fuel spray are studied in a constant-volume chamber.Microscopic spray parameters are measured by laser diffraction at different axial and radial positions downstream of the nozzle.The results show that the atomization effect is inhibited linearly with the increase of mass concentration.The increase of injection pressure promotes the droplet breakup.However,the trend gradually weakens and becomes more noticeable at high concentrations.Comparing with the concentration,the influence of the injection pressure on the atomization characteristics is dominant.Although low concentration and high injection pressure can promote the droplet breakup,they also increase the probability of droplet collision,resulting in droplet aggregation.This is more evident in low-viscosity fuels.The droplet size increases in the axial direction owing to the aggregation.However,the diameter decreases in the radial direction owing to the outward deflection of small droplets caused by air turbulence and entrainment.In addition,the high-velocity airflow significantly promotes the droplet breakup near the nozzle and spray axis regions and inhibits the aggregation effect.However,the lower-viscosity fuels keep smaller droplet sizes and better atomization in the whole spraying process,which is easier to realize than the higher-viscosity fuels.Overall,low concentration,high injection pressure,and low viscosity of fuel have beneficial effects on the droplet breakup.This is very important for improving the atomization effect of fuel.
文摘As a requisite to determining management practice effects on stored soil organic carbon (SOC) stock in a landscape unit, the baseline SOC stock with depth must be determined and the land use, management practices and erosion-induced changes measured periodically or over a period of time. The SOC loss and additions due to soil erosion, transport and deposition must be accounted for or be quantified when determining the real impact of the management practices on net SOC stock over time. Quantifying the SOC loss due to erosion will help avoid over estimation of the management practice performances. Appropriate soil sampling designs and sampling procedures are needed to establish a SOC stock baseline and to monitor and verify new SOC storage or sequestration as a result of a management practice. The Dinesen Prairie landscape in western Iowa, USA was sampled to provide a SOC stock baseline and then the adjacent cropland was sampled to determine the past impact of land use change, management practices and erosion on SOC stock retention. After 100 to 150 years of farming, the entire cropland landscape retained only 49% of the baseline prairie SOC stock. Only the cropland toe-slope (TS) retained more SOC stock than the prairie TS as a result of the erosion, transport and deposition of SOC rich sediment on the TS.
文摘An explicitly coupled two-dimensional (2D) multiphysics finite element method (FEM) framework comprised of thermal, phase field, mechanical and electromagnetic (TPME) equations was developed to simulate the conversion of solid kerogen in oil shale to liquid oil through </span><i><span style="font-family:Verdana;font-size:12px;">in-situ</span></i><span style="font-family:Verdana;font-size:12px;"> pyrolysis by radio frequency heating. Radio frequency heating as a method of <i></span><i><span style="font-family:Verdana;font-size:12px;">in-situ</span></i><span style="font-family:Verdana;font-size:12px;"></i> pyrolysis represents a tenable enhanced oil recovery method, whereby an applied electrical potential difference across a target oil shale formation is converted to thermal energy, heating the oil shale and causing it to liquify to become liquid oil. A number of <i></span><i><span style="font-family:Verdana;font-size:12px;">in-situ</span></i><span style="font-family:Verdana;font-size:12px;"></i> pyrolysis methods are reviewed but the focus of this work is on the verification of the TPME numerical framework to model radio frequency heating as a potential dielectric heating process for enhanced oil recovery.</span></span><span style="font-size:10pt;font-family:""> </span><span style="font-family:Verdana;">Very few studies exist which describe production from oil shale;furthermore, there are none that specifically address the verification of numerical models describing radio frequency heating. As a result, the Method of Manufactured Solutions (MMS) was used as an analytical verification method of the developed numerical code. Results show that the multiphysics finite element framework was adequately modeled enabling the simulation of kerogen conversion to oil as a part of the analysis of a TPME numerical model.
文摘The effect of UV- and 137Cs gamma radiation on the structural and chemical integrity of human hair was studied to determine the feasibility of using human hair as a non-invasive biomarker of radiation exposure to ionized gamma- and non-ionized UV-radiation. Steady state tryptophan (Trp) fluorescence and chemical analytical methods were used to evaluate the molecular integrity of Trp fluorophores and SH-groups in hair proteins and to assess the radiation induced damage quantitatively. It was found that human hair fibers were progressively damaged by exposure to both UV- and ionized gamma radiation. Damage to the hair was evidenced by a decrease in the fluorescence intensity as a result of observed depletion of the amino acid tryptophan as well as significant reduction in a number of free SH-groups in hair proteins. Hair damage was dose-dependent for exposures between 0 and 10.0 Gy and 0 - 20 J/cm2 of UV-radiation. Additional results demonstrate that hair-fibers exposed to gamma rays, with much higher quantum energy than UV, undergo a smaller extent of changes in Trp fluorescence than when exposed to lower or equal energy of UV-irradiation. The stable Trp fluorophore appears to be extremely sensitive to UV-radiation in contrast to the ionized gamma radiation whose damage is originated from the reaction of free radicals and direct deposition of energy. We conclude that fluorescence spectroscopy represents a useful tool in the quantitative evaluation of the radiation exposure and could also be used for the rapid and non-invasive assessment of radiation dose i.e. biodosimeter. The approach is simple, non-invasive and appears to have considerable potential that enables quantitative evaluation of radiation dose exposure in a single hair fiber.
