Subcritical reactors(SCRs)or subcritical assemblies(SCAs)are the main infrastructure for designing power reactors.These reactors are widely used for training and research because of their high level of inherent safety...Subcritical reactors(SCRs)or subcritical assemblies(SCAs)are the main infrastructure for designing power reactors.These reactors are widely used for training and research because of their high level of inherent safety.The objective of this study is to design a subcritical reactor using a pressurized water reactor(PWR)conventional fuel following two safety points.In the first approach,deeply placed SCR cores with an infinite multiplication factor(k_(∞))of less than unity were identified using the DRAGON lattice code.In the second approach,subcritical reactor cores with an effective multiplication factor(k_(eff))of less than unity were determined by coupling the cell calculations of the DRAGON lattice code and core calculations of the DONJON code.For the deeply subcritical reactor design,it was found that the reactor would remain inherently subcritical while using fuel rods with ^(235)U enrichment of up to 0.9%,regardless of the pitch of the fuel rods.In the second approach,the optimal pitches(1.3 to 2.3 cm)were determined for different fuel enrichment values from 1 to 5%.Subsequently,the k_(eff) was obtained for a fuel rod arrangement of 8×8 to 80×80,and the states in which the reactor would be subcritical were determined for different fuel enrichments at the corresponding optimal pitch.To validate the models used in the DRAGON and DONJON codes,the k_(eff) of the Isfahan Light Water Subcritical Reactor(LWSCR)was experimentally measured and compared with the results of the calculations.Finally,the effects of fuel and moderator temperature changes were investigated to ensure that the designed assemblies remained in the subcritical state at all operational temperatures.展开更多
The freeze-thaw process is crucial for forming soil macropore structure to promote movement of water and salt downward by preferential flow in seasonally frozen regions.However,the freeze-thaw process of soil is hinde...The freeze-thaw process is crucial for forming soil macropore structure to promote movement of water and salt downward by preferential flow in seasonally frozen regions.However,the freeze-thaw process of soil is hindered by the snowpack,and the effects of the snowpack on the soil macropore structure and its implications on the formation of preferential flow are not well understood.This study collected soil samples from Da’an City,Northeast China,on July 15 and 16,2022,and conducted an indoor soil column snowpack-freeze-thaw tracing experiment on October 10 to 30,2022,to reveal the impact of snowpack and freeze-thaw cycles(FTC)on the forma-tion of preferential flow.The experiments were carried out with three levels of initial moisture content(IMC)of the soil column,the times of freeze-thaw cycles(T-FTC),and the snowpack thickness(SPT).Results show that increases in both IMC and SPT decreased the max infiltration depth(MID)of preferential flow.Greater T-FTC increased the MID and non-uniformity of the wet front trace and promoted the creation of preferential flow.The T-FTC and IMC both increased the overall variability of preferential flow,but this vari-ability decreased with greater SPT.The length index(LI)had the most significant impact on the preferential flow index(PFI)with an entropy weight of 0.2340,while the height difference of the multifractal spectrum(Δf(α))had the most negligible impact with a weight of 0.0753.Finally,results of redundancy analysis(RDA)and structural equation model(SEM)show that multifractal characteristic in-dicators have a much stronger ability to reflect the degree of preferential flow than developmental characteristic indicators.The T-FTC was the most important factor driving the formation of preferential flow in snowpack-freeze-thaw cycles.Therefore,conducting re-search on preferential flow in cold and arid regions is greatly significant for the utilization of regional water resources and the improve-ment of soil ecological environments.展开更多
In China,approximately 13% of people living with human immunodeficiency virus(HIV)(PLWH)are receiving lopinavir/ritonavir(LPV/r)-based regimens.These PLWH typically have a history of either treatment failure or intole...In China,approximately 13% of people living with human immunodeficiency virus(HIV)(PLWH)are receiving lopinavir/ritonavir(LPV/r)-based regimens.These PLWH typically have a history of either treatment failure or intolerance to first-line efavirenz-based regimens.Given the considerable pill burden and adverse effects associated with LPV/r,treatment optimization is important for this population.This multicenter retrospective study aimed to evaluate the efficacy and safety of switching from LPV/r-based regimens to the single-tablet regimen of bictegravir/emtricitabine/tenofovir alafenamide(BIC/FTC/TAF).Virological suppression rates(HIV-RNA<40 copies/mL)were primarily compared between the 48-week periods before and after switching to BIC/FTC/TAF.CD4 counts and metabolic data were also assessed.A total of 461 PLWH were recruited between January 2021 and December 2023,with 92.2% being male,a median age of 38 years,and a median antiretroviral therapy duration of 8 years.Prior to initiating LPV/r,23.0%(106/461)had documented virological failure.During LPV/r treatment,18.9%(20/106)of these individuals experienced viral rebound.Among all participants,the overall virological suppression rates significantly increased from 94.6%(pre-switch)to 98.6%(post-switch)(P<0.001).Notably,among participants with prior virological failure,suppression rates improved significantly from 81.1%to 97.2%(P<0.001),whereas no significant difference was observed in those without such history(from 98.6% to 99.2%,P=0.764).The median triglyceride level decreased from 2.4 mmol/L to 1.8 mmol/L(P<0.001),while no difference in CD4 counts was observed.These findings demonstrate that BIC/FTC/TAF is an effective and metabolically favorable treatment option for PLWH switching from LPV/r based regimens,regardless of whether they have a prior history of virological failure.展开更多
This paper presents a comprehensive survey of fault diagnosis and fault tolerant approaches for permanent magnet synchronous machines(PMSM).PMSMs are prominent in the pervading usage of electric motors,for their high ...This paper presents a comprehensive survey of fault diagnosis and fault tolerant approaches for permanent magnet synchronous machines(PMSM).PMSMs are prominent in the pervading usage of electric motors,for their high efficiency,great robustness,reliability and low torque inertia.In spite of their extensive appliance,they can be quite non-resilient and inadequate in operation when faults appear in motor drive apparatus such as inverters,stator windings,sensors,etc.These may lead to insulation failure,torque fluctuations,overcurrent or even system collapse.On that account,fault diagnosis and fault tolerant methods are equipped to enhance the stability and robustness in PMSMs.Progressive methodologies of PMSM fault diagnosis and tolerance are classified,discussed,reviewed and compared in this paper,beginning with mat hematical modeling of PMSM and then scrutinizing various fault conditions in PMSMs.Finally,the scope of research on the topic is highlighted.The contribution of this review is to emphasize optimistic schemes and to assist researchers with the latest trends in this field for future directions.展开更多
Cases of COVID-19 and its variant omicron are raised all across the world.The most lethal form and effect of COVID-19 are the omicron version,which has been reported in tens of thousands of cases daily in numerous nat...Cases of COVID-19 and its variant omicron are raised all across the world.The most lethal form and effect of COVID-19 are the omicron version,which has been reported in tens of thousands of cases daily in numerous nations.Following WHO(World health organization)records on 30 December 2021,the cases of COVID-19 were found to be maximum for which boarding individuals were found 1,524,266,active,recovered,and discharge were found to be 82,402 and 34,258,778,respectively.While there were 160,989 active cases,33,614,434 cured cases,456,386 total deaths,and 605,885,769 total samples tested.So far,1,438,322,742 individuals have been vaccinated.The coronavirus or COVID-19 is inciting panic for several reasons.It is a new virus that has affected the whole world.Scientists have introduced certain ways to prevent the virus.One can lower the danger of infection by reducing the contact rate with other persons.Avoiding crowded places and social events withmany people reduces the chance of one being exposed to the virus.The deadly COVID-19 spreads speedily.It is thought that the upcoming waves of this pandemicwill be evenmore dreadful.Mathematicians have presented severalmathematical models to study the pandemic and predict future dangers.The need of the hour is to restrict the mobility to control the infection from spreading.Moreover,separating affected individuals from healthy people is essential to control the infection.We consider the COVID-19 model in which the population is divided into five compartments.The present model presents the population’s diffusion effects on all susceptible,exposed,infected,isolated,and recovered compartments.The reproductive number,which has a key role in the infectious models,is discussed.The equilibrium points and their stability is presented.For numerical simulations,finite difference(FD)schemes like nonstandard finite difference(NSFD),forward in time central in space(FTCS),and Crank Nicolson(CN)schemes are implemented.Some core characteristics of schemes like stability and consistency are calculated.展开更多
This research paper represents a numerical approximation to three interesting equations of Fisher, which are linear, non-linear and coupled linear one dimensional reaction diffusion equations from population genetics....This research paper represents a numerical approximation to three interesting equations of Fisher, which are linear, non-linear and coupled linear one dimensional reaction diffusion equations from population genetics. We studied accuracy in term of L∞ error norm by random selected grids along time levels for comparison with exact results. The test example demonstrates the accuracy, efficiency and versatility of the proposed schemes. It is shown that the numerical schemes give better solutions. Moreover, the schemes can be easily applied to a wide class of higher dimension non-linear reaction diffusion equations.展开更多
When filling embankment dams in cold regions,engineers must solve two freeze–thaw cycle(FTC)-induced soil problems.First,compacted soil constituting the dam is subjected to the FTC during dam construction.Second,loos...When filling embankment dams in cold regions,engineers must solve two freeze–thaw cycle(FTC)-induced soil problems.First,compacted soil constituting the dam is subjected to the FTC during dam construction.Second,loose soil material(LSM),which is subjected to the FTC,fills the dam.To investigate the effects of the aforementioned two problems on the hydraulic conductivity of compacted clayey soil,a series of permeation tests on clayey soil compacted before and after FTC were conducted in this study.The results showed that for the first problem,the hydraulic conductivity of compacted clayey soil subjected to one FTC significantly increases by two to three orders of magnitude because FTC-induced cracks can cause preferential flow in the permeation process.For the second problem,when the FTC number is less than a critical number,the FTC of the LSM may result in the development of united soil particles,thereby increasing the effective porosity ratio and hydraulic conductivity of the compacted soil.It was discovered that the hydraulic conductivity of compacted soil can increase by one to three times when the LSM is subjected to 10 FTCs.When the FTC number exceeds a critical number,the effective porosity ratio and hydraulic conductivity of the compacted soil may decrease with the FTC of the LSM.This should be investigated in future studies,and the results can be used to improve engineering management processes when filling embankment dams during winter in cold regions.展开更多
In this paper, we originate results with finite difference schemes to approximate the solution of the classical Fisher Kolmogorov Petrovsky Piscounov (KPP) equation from population dynamics. Fisher’s equation describ...In this paper, we originate results with finite difference schemes to approximate the solution of the classical Fisher Kolmogorov Petrovsky Piscounov (KPP) equation from population dynamics. Fisher’s equation describes a balance between linear diffusion and nonlinear reaction. Numerical example illustrates the efficiency of the proposed schemes, also the Neumann stability analysis reveals that our schemes are indeed stable under certain choices of the model and numerical parameters. Numerical comparisons with analytical solution are also discussed. Numerical results show that Crank Nicolson and Richardson extrapolation are very efficient and reliably numerical schemes for solving one dimension fisher’s KPP equation.展开更多
文摘Subcritical reactors(SCRs)or subcritical assemblies(SCAs)are the main infrastructure for designing power reactors.These reactors are widely used for training and research because of their high level of inherent safety.The objective of this study is to design a subcritical reactor using a pressurized water reactor(PWR)conventional fuel following two safety points.In the first approach,deeply placed SCR cores with an infinite multiplication factor(k_(∞))of less than unity were identified using the DRAGON lattice code.In the second approach,subcritical reactor cores with an effective multiplication factor(k_(eff))of less than unity were determined by coupling the cell calculations of the DRAGON lattice code and core calculations of the DONJON code.For the deeply subcritical reactor design,it was found that the reactor would remain inherently subcritical while using fuel rods with ^(235)U enrichment of up to 0.9%,regardless of the pitch of the fuel rods.In the second approach,the optimal pitches(1.3 to 2.3 cm)were determined for different fuel enrichment values from 1 to 5%.Subsequently,the k_(eff) was obtained for a fuel rod arrangement of 8×8 to 80×80,and the states in which the reactor would be subcritical were determined for different fuel enrichments at the corresponding optimal pitch.To validate the models used in the DRAGON and DONJON codes,the k_(eff) of the Isfahan Light Water Subcritical Reactor(LWSCR)was experimentally measured and compared with the results of the calculations.Finally,the effects of fuel and moderator temperature changes were investigated to ensure that the designed assemblies remained in the subcritical state at all operational temperatures.
基金Under the auspices of the Natural Science Foundation of China(No.42272299)The Key Projects of Jilin Provincial Department of Science and Technology(No.20240203004NC)+1 种基金National Key Research and Development Program of China(No.2022YFD1500500)Graduate Innovation Fund of Jilin University(No.2024CX111)。
文摘The freeze-thaw process is crucial for forming soil macropore structure to promote movement of water and salt downward by preferential flow in seasonally frozen regions.However,the freeze-thaw process of soil is hindered by the snowpack,and the effects of the snowpack on the soil macropore structure and its implications on the formation of preferential flow are not well understood.This study collected soil samples from Da’an City,Northeast China,on July 15 and 16,2022,and conducted an indoor soil column snowpack-freeze-thaw tracing experiment on October 10 to 30,2022,to reveal the impact of snowpack and freeze-thaw cycles(FTC)on the forma-tion of preferential flow.The experiments were carried out with three levels of initial moisture content(IMC)of the soil column,the times of freeze-thaw cycles(T-FTC),and the snowpack thickness(SPT).Results show that increases in both IMC and SPT decreased the max infiltration depth(MID)of preferential flow.Greater T-FTC increased the MID and non-uniformity of the wet front trace and promoted the creation of preferential flow.The T-FTC and IMC both increased the overall variability of preferential flow,but this vari-ability decreased with greater SPT.The length index(LI)had the most significant impact on the preferential flow index(PFI)with an entropy weight of 0.2340,while the height difference of the multifractal spectrum(Δf(α))had the most negligible impact with a weight of 0.0753.Finally,results of redundancy analysis(RDA)and structural equation model(SEM)show that multifractal characteristic in-dicators have a much stronger ability to reflect the degree of preferential flow than developmental characteristic indicators.The T-FTC was the most important factor driving the formation of preferential flow in snowpack-freeze-thaw cycles.Therefore,conducting re-search on preferential flow in cold and arid regions is greatly significant for the utilization of regional water resources and the improve-ment of soil ecological environments.
基金supported by the Capital's Funds for Health Improvement and Research(CFH2024-2-2175).
文摘In China,approximately 13% of people living with human immunodeficiency virus(HIV)(PLWH)are receiving lopinavir/ritonavir(LPV/r)-based regimens.These PLWH typically have a history of either treatment failure or intolerance to first-line efavirenz-based regimens.Given the considerable pill burden and adverse effects associated with LPV/r,treatment optimization is important for this population.This multicenter retrospective study aimed to evaluate the efficacy and safety of switching from LPV/r-based regimens to the single-tablet regimen of bictegravir/emtricitabine/tenofovir alafenamide(BIC/FTC/TAF).Virological suppression rates(HIV-RNA<40 copies/mL)were primarily compared between the 48-week periods before and after switching to BIC/FTC/TAF.CD4 counts and metabolic data were also assessed.A total of 461 PLWH were recruited between January 2021 and December 2023,with 92.2% being male,a median age of 38 years,and a median antiretroviral therapy duration of 8 years.Prior to initiating LPV/r,23.0%(106/461)had documented virological failure.During LPV/r treatment,18.9%(20/106)of these individuals experienced viral rebound.Among all participants,the overall virological suppression rates significantly increased from 94.6%(pre-switch)to 98.6%(post-switch)(P<0.001).Notably,among participants with prior virological failure,suppression rates improved significantly from 81.1%to 97.2%(P<0.001),whereas no significant difference was observed in those without such history(from 98.6% to 99.2%,P=0.764).The median triglyceride level decreased from 2.4 mmol/L to 1.8 mmol/L(P<0.001),while no difference in CD4 counts was observed.These findings demonstrate that BIC/FTC/TAF is an effective and metabolically favorable treatment option for PLWH switching from LPV/r based regimens,regardless of whether they have a prior history of virological failure.
文摘This paper presents a comprehensive survey of fault diagnosis and fault tolerant approaches for permanent magnet synchronous machines(PMSM).PMSMs are prominent in the pervading usage of electric motors,for their high efficiency,great robustness,reliability and low torque inertia.In spite of their extensive appliance,they can be quite non-resilient and inadequate in operation when faults appear in motor drive apparatus such as inverters,stator windings,sensors,etc.These may lead to insulation failure,torque fluctuations,overcurrent or even system collapse.On that account,fault diagnosis and fault tolerant methods are equipped to enhance the stability and robustness in PMSMs.Progressive methodologies of PMSM fault diagnosis and tolerance are classified,discussed,reviewed and compared in this paper,beginning with mat hematical modeling of PMSM and then scrutinizing various fault conditions in PMSMs.Finally,the scope of research on the topic is highlighted.The contribution of this review is to emphasize optimistic schemes and to assist researchers with the latest trends in this field for future directions.
基金supported by the research grants Seed ProjectPrince Sultan UniversitySaudi Arabia SEED-2022-CHS-100.
文摘Cases of COVID-19 and its variant omicron are raised all across the world.The most lethal form and effect of COVID-19 are the omicron version,which has been reported in tens of thousands of cases daily in numerous nations.Following WHO(World health organization)records on 30 December 2021,the cases of COVID-19 were found to be maximum for which boarding individuals were found 1,524,266,active,recovered,and discharge were found to be 82,402 and 34,258,778,respectively.While there were 160,989 active cases,33,614,434 cured cases,456,386 total deaths,and 605,885,769 total samples tested.So far,1,438,322,742 individuals have been vaccinated.The coronavirus or COVID-19 is inciting panic for several reasons.It is a new virus that has affected the whole world.Scientists have introduced certain ways to prevent the virus.One can lower the danger of infection by reducing the contact rate with other persons.Avoiding crowded places and social events withmany people reduces the chance of one being exposed to the virus.The deadly COVID-19 spreads speedily.It is thought that the upcoming waves of this pandemicwill be evenmore dreadful.Mathematicians have presented severalmathematical models to study the pandemic and predict future dangers.The need of the hour is to restrict the mobility to control the infection from spreading.Moreover,separating affected individuals from healthy people is essential to control the infection.We consider the COVID-19 model in which the population is divided into five compartments.The present model presents the population’s diffusion effects on all susceptible,exposed,infected,isolated,and recovered compartments.The reproductive number,which has a key role in the infectious models,is discussed.The equilibrium points and their stability is presented.For numerical simulations,finite difference(FD)schemes like nonstandard finite difference(NSFD),forward in time central in space(FTCS),and Crank Nicolson(CN)schemes are implemented.Some core characteristics of schemes like stability and consistency are calculated.
文摘This research paper represents a numerical approximation to three interesting equations of Fisher, which are linear, non-linear and coupled linear one dimensional reaction diffusion equations from population genetics. We studied accuracy in term of L∞ error norm by random selected grids along time levels for comparison with exact results. The test example demonstrates the accuracy, efficiency and versatility of the proposed schemes. It is shown that the numerical schemes give better solutions. Moreover, the schemes can be easily applied to a wide class of higher dimension non-linear reaction diffusion equations.
基金supported by the National Natural Science Foundation of China(Grant No.41801039,42071095,41771066)the Second Tibetan Plateau ReferencesScientific Expedition and Research(STEP)program(Grant No.2019QZKK0905)+1 种基金the Science and Technology Project of Gansu Province(Grant No.21JR7RA052)the Science and Technology Project of Yalong River Hydropower Development Company(LHKA-G201906)。
文摘When filling embankment dams in cold regions,engineers must solve two freeze–thaw cycle(FTC)-induced soil problems.First,compacted soil constituting the dam is subjected to the FTC during dam construction.Second,loose soil material(LSM),which is subjected to the FTC,fills the dam.To investigate the effects of the aforementioned two problems on the hydraulic conductivity of compacted clayey soil,a series of permeation tests on clayey soil compacted before and after FTC were conducted in this study.The results showed that for the first problem,the hydraulic conductivity of compacted clayey soil subjected to one FTC significantly increases by two to three orders of magnitude because FTC-induced cracks can cause preferential flow in the permeation process.For the second problem,when the FTC number is less than a critical number,the FTC of the LSM may result in the development of united soil particles,thereby increasing the effective porosity ratio and hydraulic conductivity of the compacted soil.It was discovered that the hydraulic conductivity of compacted soil can increase by one to three times when the LSM is subjected to 10 FTCs.When the FTC number exceeds a critical number,the effective porosity ratio and hydraulic conductivity of the compacted soil may decrease with the FTC of the LSM.This should be investigated in future studies,and the results can be used to improve engineering management processes when filling embankment dams during winter in cold regions.
文摘In this paper, we originate results with finite difference schemes to approximate the solution of the classical Fisher Kolmogorov Petrovsky Piscounov (KPP) equation from population dynamics. Fisher’s equation describes a balance between linear diffusion and nonlinear reaction. Numerical example illustrates the efficiency of the proposed schemes, also the Neumann stability analysis reveals that our schemes are indeed stable under certain choices of the model and numerical parameters. Numerical comparisons with analytical solution are also discussed. Numerical results show that Crank Nicolson and Richardson extrapolation are very efficient and reliably numerical schemes for solving one dimension fisher’s KPP equation.
