This study experimentally investigates the influence of surfacewettability on the frosting characteristics of three types of corrugated structures(Types A,B,and C)under controlled low-temperature conditions.The experi...This study experimentally investigates the influence of surfacewettability on the frosting characteristics of three types of corrugated structures(Types A,B,and C)under controlled low-temperature conditions.The experiments were conducted in a constant-temperature bath at a cold surface temperature of–5℃,relative humidity of 90%,and ambient air temperature of 10℃.The results reveal that the variation trends of frost morphology,frost mass,and frost layer thickness are generally consistent across surfaces with different wettability.Among the tested surfaces,frost crystal formation and complete surface coverage occurred latest on the superhydrophobic surface(CA=153.9–165.8℃),next on the bare aluminumsurface(75.3–83.2℃),and earliest on the hydrophilic surface(5.3–7.5℃).At the same frosting duration,the superhydrophobic surface exhibited a sparse and fluffy frost layer,the bare aluminum surface formed a rough and dense frost,while the hydrophilic surface developed a fine and compact frost layer.The amount of frost formation decreased in the order of hydrophilic>bare aluminum>superhydrophobic,indicating that the superhydrophobic surface provides the most significant anti-frosting effect during the initial stages of frost formation.For instance,on the Type A corrugated structure,after 15 min of frosting,the frost mass on the superhydrophobic surface was 38.78%and 68.45%lower than those on the bare aluminum and hydrophilic surfaces,respectively.After 30 min,these differences were 4.99%and 25.26%,respectively.Overall,the superhydrophobic surface exhibited the smallest frost mass and frost layer thickness,demonstrating superior anti-frosting performance compared with the other surface types.展开更多
Freeze-thaw(F-T)cycle is receiving increasing attention as a primary threat to the long-term stability of rock engineering in high-elevation regions.In this study,artificial F-T cycle tests are first conducted on pre-...Freeze-thaw(F-T)cycle is receiving increasing attention as a primary threat to the long-term stability of rock engineering in high-elevation regions.In this study,artificial F-T cycle tests are first conducted on pre-flawed sandstone specimens with real-time frost heave pressure(FHP)monitoring,followed by subsequent cyclic loading tests with different maximum stresses.Given the water-ice-sandstone interaction,the evolution process of FHP in flaws can be divided into six phases,i.e.initial,silence,eruption,reduction,second-arising,and dissipation phases.Its magnitude exhibits an exponential decrease with increasing F-T cycle number.The influences of F-T cycles and the maximum stress on the fatigue mechanical characteristics of flawed sandstone are revealed.Subjected to higher F-T cycles and maximum stress,larger irreversible strain and less dissipated energy are accumulated inside flawed sandstone specimens,leading to faster damage and lower fatigue life.The three-stage evolution characters of irreversible strain and dissipated energy are both weakened by repeated F-T treatment,i.e.the prolonged initial and accelerated stages and shortened stable stage.In addition,the repeated F-T cycles diminish the impact of prefabricated flaws on cracking behavior of flawed sandstone specimens,and the fatigue failure pattern changes from shear-dominated failure with a transfixion shear band to tensile-dominated failure with massive tensile cracks as the F-T cycle number increases.Employing the scanning electron microscopy(SEM),the underlying damage mechanisms of flawed rocks under the coupling effect of F-T treatment and cyclic loading are discussed.Finally,an F-T-fatigue damage model is proposed based on FHP evolution and irreversible strain,which possesses distinct physical significance and reasonably quantifies the F-T deterioration and fatigue damage accumulation of flawed rocks.展开更多
We investigated the effects of fly ash(FA)content on the mechanical properties of recycled aggregate concrete(RAC)and its regeneration potential under freeze and thaw(F-T)cycles.The physical properties of second-gener...We investigated the effects of fly ash(FA)content on the mechanical properties of recycled aggregate concrete(RAC)and its regeneration potential under freeze and thaw(F-T)cycles.The physical properties of second-generation recycled concrete aggregates(RCA)were used to analyze the regeneration potential of RAC after F-T cycles.Scanning electron microscopy was used to study the interfacial transition zone microstructure of RAC after F-T cycles.Results showed that adding 20%FA to RAC significantly enhanced its mechanical properties and frost resistance.Before the F-T cycles,the compressive strength of RAC with 20%FA reached 48.3 MPa,exceeding research strength target of 40 MPa.A majority of second-generation RCA with FA had been verified to attain class Ⅲ,which enabled their practical application in non-structural projects such as backfill trenches and road pavement.However,the second-generation RCA with 20%FA can achieve class Ⅱ,making it ideal for 40 MPa structural concrete.展开更多
Considering the comprehensive morphology and genesis of Podzols of the Stolowe Mountains,and the still-possible impact of frost actions and other processes related to cold climate on these soils,the main aims of this ...Considering the comprehensive morphology and genesis of Podzols of the Stolowe Mountains,and the still-possible impact of frost actions and other processes related to cold climate on these soils,the main aims of this study were to determine whether(i)the heterogeneous Podzols in the Stolowe Mountains underwent a phase of development in a cold climate,resulting in frost action features visible on the micromorphological level,and whether(ii)contemporary cryopedogenic traces are masked by the translocation of organic matter due to the podzolisation process.Four soil profiles were investigated,revealing distinct layers corresponding to different periods of soil formation.Under field observation,no explicit frost-related characteristics were observed.Nevertheless,micromorphological analysis revealed cappings of fine materials on grains or peds,as well as development of granostriated(or any striated)b-fabric that resulted from the alternating effects of thawing and freezing processes.Moreover,micromorphological analysis revealed the presence of microstructures that could be the result of cryogenic processes,such as platy,angular blocky and lenticular features,as well as plane,vugh and star-shaped void types.The translocation of organic matter during podzolisation modified or concealed the frost-related features that developed during the late Pleistocene and early Holocene.This is evident,for instance,in the accumulation of organic matter on cappings and within soil voids,which further hinders the identification of frost-related characteristics and the interpretation of the soil's evolution.Macromorphological observations enhanced with micromorphological analyses revealed three distinct layers:(i)a young upper layer composed of loose,sandy material;(ii)a deeper layer containing a spodic horizon with frost actions,involving pedofeatures associated with the Pleistocene cold climate and(iii)a deeper subsoil basal layer.The abovementioned microstructures,combined with lithological discontinuity,support the hypothesised polygenetic origin of Podzols in the studied region.展开更多
In cold regions,the frost-heave of soil can cause uneven railway subgrades,affecting the safety and efficiency of high-speed railways.This study proposes a novel PCW-iTransformer model for predicting frost heave,which...In cold regions,the frost-heave of soil can cause uneven railway subgrades,affecting the safety and efficiency of high-speed railways.This study proposes a novel PCW-iTransformer model for predicting frost heave,which integrates PCHIP data interpolation,CEEMDAN signal decomposition,and WPT denoising to extract sequential features.Compared to existing models like Autoformer,Crossformer,and DLinear,PCW-iTransformer achieves a reduction of 19.1%-34.5%in error metrics and an improvement of 2.8%-4.6%in the coefficient of determination.Additionally,a fused parameter model based on normalized moisture and temperature improves prediction accuracy,reducing MSE,MAE,and RMSE by up to 7.6%.The model also demonstrates robustness under data scarcity,maintaining stable performance with 40%continuous or 60%random missing data.Overall,PCW-iTransformer provides a reliable approach for predicting frost heave,offering valuable insights for the maintaining and long-term stability of high-speed railway subgrades in cold regions.展开更多
Frost accumulation on the evaporator fins of air source heat pumps(ASHPs)severely degrades heat transfer performance and overall system efficiency.To address this,the present study employs computational fluid dynamics...Frost accumulation on the evaporator fins of air source heat pumps(ASHPs)severely degrades heat transfer performance and overall system efficiency.To address this,the present study employs computational fluid dynamics(CFD)to investigate how fin spacing influences frosting behavior,emphasizing the coupled evolution of frost thickness,density,airflow,and temperature distribution within fin channels.Results reveal that fin spacing is a key parameter governing both the extent and rate of frost growth.Wider fin spacing enhances frost accumulation,with a final frost mass of 6.41 g at 12 mm,about 71.8%higher than at 4 mm.In contrast,narrower spacing suppresses frost formation by accelerating airflow.The frost layer exhibits a distinct two-stage growth pattern:at 12 mm spacing,the early-stage average thickness growth rate reaches 0.021 mm/min,nearly 4.3 times that at 4 mm.Frost density follows similar initial trends across different spacings but diverges later due to thermal resistance and airflow variations.展开更多
Uneven frost heave deformation can shorten the operational lifespan of foundation engineering.Clarifying the mechanisms of uneven frost heave facilitates the targeted mitigation of frost damage.This study focused on a...Uneven frost heave deformation can shorten the operational lifespan of foundation engineering.Clarifying the mechanisms of uneven frost heave facilitates the targeted mitigation of frost damage.This study focused on a water conveyance channel in Jilin Province,northern China,and found after monitoring that the frost heave at the channel bottom lining exceeded that at the crest by 44.5 mm,with the freezing temperature at the bottom being over 2℃lower than that at the crest.Soil columns with an initial gravimetric moisture content of 12%,16%,18%,and 20%were then prepared.The effects of temperature and moisture content on frost heave were analyzed under two freezing conditions(-5℃and-10℃)through unidirectional freezing tests.A coupled thermo-hydro-mechanical(THM)frost heave model,validated by the test results,was further established.In the soil with an initial moisture content of 20%,the formation of ice lenses associated with substantial water migration contributed to a large temperature gradient,which can jointly induce frost heave.Under the-10℃condition,the temperature gradient in the soil column with a 20%initial moisture content reached 0.84℃/cm,the total water migration reached 10.72%,and the frost heave deformation was 1.86 mm.The THM coupling results indicated that,under the interaction of a large temperature gradient and moisture accumulation,the volumetric ice content remained high in the bottom soil during freezing and peaked at 0.36.The frost damage to the bottom soil was severe,and the maximum deformation reached 57 mm.展开更多
One reference in the original manuscript contained incorrect bibliographic information and cited a non-existent publication:Traczyk A(1999)Pleistocene debris cover beds and block-debris tongues in the north-western pa...One reference in the original manuscript contained incorrect bibliographic information and cited a non-existent publication:Traczyk A(1999)Pleistocene debris cover beds and block-debris tongues in the north-western part of theŚlęża Massif(Poland)and their formation under permafrost conditions.Geographia Polonica 81(1).This erroneous reference has now been removed from the references list.展开更多
Frost heave in water-bearing rock masses poses significant threats to geotechnical engineering.This paper developed a novel three-dimensional(3D)frost model,based on the combined finite-discrete element method(FDEM),t...Frost heave in water-bearing rock masses poses significant threats to geotechnical engineering.This paper developed a novel three-dimensional(3D)frost model,based on the combined finite-discrete element method(FDEM),to investigate the frost heave process in rock masses where thermal transfer,water migration,water-ice phase transition(ice growth)and ice-rock interaction are explicitly simulated.The proposed model is first validated against existing experimental and analytical solutions,and further applied to investigate path-dependent frost heave behavior under various freezing conditions.Results show that freezing direction plays a vital role in the dynamic ice growth and ice-rock interaction,thus affecting the frost heave behavior.In the top-down freezing regime,ice plugs form first at the crack's top surface,sealing the crack and preventing water migration,which can amplify ice pressure.Parametric studies,including rock Young's modulus,ice-rock friction,and rock hydraulic conductivity,further reveal that the temporal aspects of ice development and rock mechanical response strongly affect ice-rock interaction and hence the frost heave mechanism.Furthermore,some typical phenomena(e.g.water/ice extrusion and frost cracking)can also be well captured in this model.This novel numerical framework sheds new light on frost heave behavior and enriches our understanding of frost heave mechanisms and ice-rock interaction processes within cold environment engineering projects.展开更多
Frost heave in seasonally frozen regions is a one-dimensional process that could severely damage infrastructure subgrades.Stress state,temperature and water migration are important factors for frost heave.This work in...Frost heave in seasonally frozen regions is a one-dimensional process that could severely damage infrastructure subgrades.Stress state,temperature and water migration are important factors for frost heave.This work investigated the effects of soil temperature and volumetric water content on the transient frost heave ratio during the freezing of saturated silty clay in an open system and analyzed the relationships between the transient frost heave ratio and freezing rate and between temperature gradient and frost heave rate.The results show that the frost heave ratio,frost heave rate,and freezing rate are positively correlated with the temperature gradient since the temperature gradient drives the water migration during freezing,indicating the transient temperature gradient could be used to evaluate the frost heave of saturated silty clay.The transient freezing rate and transient frost heave ratio are logarithmically related to the transient frost heave ratio and transient temperature gradient,respectively.The effects of transient temperature gradient on frost heave are the principal mechanism responsible for different frost heave characteristics and uneven frost heave along a subgrade of the same soil type.展开更多
Climate change differentially influences the frozen ground,a major dynamic component of the cryosphere,on a local and regional scale.Under the warming climate with pronounced effects reported at higher altitudes,the c...Climate change differentially influences the frozen ground,a major dynamic component of the cryosphere,on a local and regional scale.Under the warming climate with pronounced effects reported at higher altitudes,the characterization of the frozen ground is very important in the Upper Indus Basin(UIB),an important and critical region with respect to climate and hydro-glaciological dynamics.In this study,the efficiency and reliability of the surface frost number model are assessed in delineating the spatial extent of different classes of frozen ground in the region.The daily MODIS land surface temperature(LST)with ground surface temperature(GST)and surface geomorphological expressions as ground validation datasets are used jointly in efficiently determining the extent of different classes of frozen ground(continuous and discontinuous permafrost and seasonal frost).The LST and GST resonate with each other in the annual cycle of temperature variation,however,with mean annual LST exhibiting an offset(cold bias)of 5 to 7℃relative to mean GST.This study shows that the highest permafrost extent is observed in areas where the lowest thinning rates of glacier ice are reported and vice versa.The surface frost number model categorizes an area of 38%±3%and 15%±3%in the UIB as permafrost and seasonal frost,respectively.Based on the altitude model,the lower limit of alpine permafrost is approximated at a mean altitude of 4919±590 m a.s.l.in the UIB.The present study acts as preliminary work in the data sparse and inaccessible regions of the UIB in characterizing the frozen and unfrozen ground and may act as a promising input data source in glaciohydro-meteorological models for the Himalaya and Karakoram.In addition,the study also underlines the consideration of this derelict cryospheric climatic variable in defining and accounting for the sustainable development of socio-economic systems through its intricate ramification on agricultural activity,landscape stability and infrastructure.展开更多
The frost growth on cold surfaces in evaporators is an undesirable phenomenon which becomes a problem for the thermal efficiency of the refrigeration systems because the ice layer acts as a thermal insulation,drastica...The frost growth on cold surfaces in evaporators is an undesirable phenomenon which becomes a problem for the thermal efficiency of the refrigeration systems because the ice layer acts as a thermal insulation,drastically reducing the rate of heat transfer in the system.Its accumulation implies an increase in energy demand and a decrease in the performance of various components involved in the refrigeration process,reducing its efficiency and making it necessary to periodically remove the frost,resulting in expenses for the defrost process.In the present work,a numerical-experimental analysis was performed in order to understand the formation process of porous ice in flat plates with different surface treatments and parameters.This understanding is of utmost importance to minimize the formation of porous ice on cold surfaces and improve equipment efficiency and performance.In this context,a low-cost experimental apparatus was developed,enabling an experimental analysis of the phenomenon under study.The environmental conditions evaluated are the temperature of the cold surface,roomtemperature,humidity,and air velocity.The material of the surfaces under study are aluminum,copper,and brass with different surface finishes,designated as smooth,grooved(hydrophilic),and varnished(hydrophobic).The numerical-experimental analysis demonstrates measurements and simulations of the thickness,surface temperature,and growth rate of the porous ice layer as a function of the elapsed time.The numerical results were in good agreement with the experimental results,indicating that the varnished surface,with hydrophobic characteristics,presents greater difficulty in providing the phenomenon.Therefore,the results showed that application of a coating allowed a significant reduction on the frost formation process contributing to the improvement of thermal efficiency and performance of refrigeration systems.展开更多
[Objective]The aim was to understand the change characteristics of sugarcane traits and evaluate the cold tolerance of sugarcane varieties under the drought and frost conditions.[Method] The experiment was carried out...[Objective]The aim was to understand the change characteristics of sugarcane traits and evaluate the cold tolerance of sugarcane varieties under the drought and frost conditions.[Method] The experiment was carried out in Ziyuan County,Guangxi Province where the frost occurred often with 21 domestic and abroad sugarcane varieties（elites）.[Result] There were significant changes in the brix,green leaf number and photosynthetic rate of sugarcane before and after light frost and decreased more in cold-sensitive varieties.However,the correlation was only significant between the damage rate of stem length and internode,percentage of green leaves after heavy frost in relation to sugarcane brix and brix changes after light frost.Further analysis showed that the evaluation for cold tolerance of sugarcane would be more simple and reliable with traits of the damage rate of stem length and percentage of upper green leaves.The evaluation for varieties indicated that if it was not carried out for cold-tolerance identification in breeding program,the percentage of sugarcane varieties with good cold-tolerance will be lower than30%,and higher than 60% with poor cold-tolerance in subtropical and tropical regions.[Conclusion] This study had provided theoretical basis for the cold-resistant evaluation of sugar cane and the breeding of the varieties of cold-resistant.展开更多
The temperate monsoon area of China is an important agricultural region but late spring frosts have frequently caused significant damage to plants there. Based on phenological data derived from the Chinese Phenologica...The temperate monsoon area of China is an important agricultural region but late spring frosts have frequently caused significant damage to plants there. Based on phenological data derived from the Chinese Phenological Observation Network （CPON）, corresponding meteorological data from 12 study sites and phenological modeling, changes in flowering times of multiple woody plants and the frequency of frost occurrence were analyzed. Through these analyses, frost risk during the flowering period at each site was estimated. Results of these estimates suggested that first flowering dates （FFD） in the study area advanced significantly from 1963 to 2009 at an average rate of -1.52 days/decade in North-east China （P〈0.01） and -2.22 days/decade （P〈0.01） in North China. Over the same period, the number of frost days in spring decreased and the last frost days advanced across the study area. Considering both flowering phenology and occurrence of frost, the frost risk index, which measures the percentage of species exposed to frost during the flowering period in spring, exhibited a decreasing trend of -0.37% per decade （insignificant） in Northeast China and -1.80% per decade （P〈0.01） in North China, implying that frost risk has reduced over the past half century. These conclusions provide important information to agriculture and forest managers in devising frost protection schemes in the region.展开更多
Automated over-tree sprinkler irrigation systems were developed and tested in two orchards located in two separate locations in southern Iran （a 0.17 ha peach orchard and a 0.24 ha orange orchard） to protect peach b...Automated over-tree sprinkler irrigation systems were developed and tested in two orchards located in two separate locations in southern Iran （a 0.17 ha peach orchard and a 0.24 ha orange orchard） to protect peach blossoms and orange trees leaves and fruits from low temperature damage. The experiment used a system that monitored the trees and air temperatures using two thermistors. The water application rate by the irrigation system was determined by an energy balance as implemented by the software FROSTPRO, In the peach orchard, the system was tested during three frost events during the spring of 2003 and three other events during the spring of 2004. The system successfully kept peach flowers above the critical temperature, i.e., -4.0℃ in spring 2004 （control block -4.12℃, and sprinkled block ＋0.5℃） during all events. Similar results were obtained in the orange orchard during three frost events in the winter of 2004, during which the tree temperatures were at least 2.5℃ above the critical temperature. Results from field tests show that the system can effectively protect the peach blossoms from damage. Determination done after the frost events showed a 12% blossom kill in the sprinkled blocks while in the unsprinkled control block a 41.5% blossom kill. Calculations indicated that when using variable application rates, the amount of water used can be reduced by 54.3%. Spatial distribution of minimum temperatures during the three frosts was also studied in Jahrom, Iran. Results showed a significant temperature control in the experimental block, especially in the central part of the orchard, but the block margins （about 3.6% of the total area） were at the risk of low temperature due to the wind drift effects.展开更多
Ground temperatures from four of the seven extensively studied highway cross-sections near Gulkana/Glennallen,Alaska during 1954;962,were chosen to better understand the impacts of highway construction on warm permafr...Ground temperatures from four of the seven extensively studied highway cross-sections near Gulkana/Glennallen,Alaska during 1954;962,were chosen to better understand the impacts of highway construction on warm permafrost.Both the thawing of permafrost and seasonal frost action impacted on road surface stability for about 6 years until the maximum summer thaw reached about 3 m in depth.Seasonal frost action caused most of the ensuing stability problems.Unusually warm summers and the lengths of time required to re-freeze the active layer were far more important than the average annual air temperatures in determining the temperatures of the underlying shallow permafrost,or the development of taliks.The hypothesized climate warming would slightly and gradually deepen the active layer and the developed under-lying talik,but its effect would be obscured by unusually warm summers,by warmer than usual winters,and by the vari-able lengths of time of the zero curtains.At least one period of climate mini-cooling in the deeper permafrost during the early 20th century was noted.展开更多
基金supported by the Science and Technology Research Project of Henan Province(No.232102241014)the Key scientific research project of Henan Province Colleges and Universities(No.22A470002)Doctoral Fund Project of Henan Polytechnic University(No.B2021-37).
文摘This study experimentally investigates the influence of surfacewettability on the frosting characteristics of three types of corrugated structures(Types A,B,and C)under controlled low-temperature conditions.The experiments were conducted in a constant-temperature bath at a cold surface temperature of–5℃,relative humidity of 90%,and ambient air temperature of 10℃.The results reveal that the variation trends of frost morphology,frost mass,and frost layer thickness are generally consistent across surfaces with different wettability.Among the tested surfaces,frost crystal formation and complete surface coverage occurred latest on the superhydrophobic surface(CA=153.9–165.8℃),next on the bare aluminumsurface(75.3–83.2℃),and earliest on the hydrophilic surface(5.3–7.5℃).At the same frosting duration,the superhydrophobic surface exhibited a sparse and fluffy frost layer,the bare aluminum surface formed a rough and dense frost,while the hydrophilic surface developed a fine and compact frost layer.The amount of frost formation decreased in the order of hydrophilic>bare aluminum>superhydrophobic,indicating that the superhydrophobic surface provides the most significant anti-frosting effect during the initial stages of frost formation.For instance,on the Type A corrugated structure,after 15 min of frosting,the frost mass on the superhydrophobic surface was 38.78%and 68.45%lower than those on the bare aluminum and hydrophilic surfaces,respectively.After 30 min,these differences were 4.99%and 25.26%,respectively.Overall,the superhydrophobic surface exhibited the smallest frost mass and frost layer thickness,demonstrating superior anti-frosting performance compared with the other surface types.
基金support from the National Natural Science Foundation of China(Grant Nos.42377144,52225904 and 52039007)supported by the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘Freeze-thaw(F-T)cycle is receiving increasing attention as a primary threat to the long-term stability of rock engineering in high-elevation regions.In this study,artificial F-T cycle tests are first conducted on pre-flawed sandstone specimens with real-time frost heave pressure(FHP)monitoring,followed by subsequent cyclic loading tests with different maximum stresses.Given the water-ice-sandstone interaction,the evolution process of FHP in flaws can be divided into six phases,i.e.initial,silence,eruption,reduction,second-arising,and dissipation phases.Its magnitude exhibits an exponential decrease with increasing F-T cycle number.The influences of F-T cycles and the maximum stress on the fatigue mechanical characteristics of flawed sandstone are revealed.Subjected to higher F-T cycles and maximum stress,larger irreversible strain and less dissipated energy are accumulated inside flawed sandstone specimens,leading to faster damage and lower fatigue life.The three-stage evolution characters of irreversible strain and dissipated energy are both weakened by repeated F-T treatment,i.e.the prolonged initial and accelerated stages and shortened stable stage.In addition,the repeated F-T cycles diminish the impact of prefabricated flaws on cracking behavior of flawed sandstone specimens,and the fatigue failure pattern changes from shear-dominated failure with a transfixion shear band to tensile-dominated failure with massive tensile cracks as the F-T cycle number increases.Employing the scanning electron microscopy(SEM),the underlying damage mechanisms of flawed rocks under the coupling effect of F-T treatment and cyclic loading are discussed.Finally,an F-T-fatigue damage model is proposed based on FHP evolution and irreversible strain,which possesses distinct physical significance and reasonably quantifies the F-T deterioration and fatigue damage accumulation of flawed rocks.
基金Funded by the Natural Science Foundation of Jiangsu Province(No.BK20220626)the National Natural Science Foundation of China(No.52078068)+2 种基金Science and Technology Innovation Foundation of NIT(No.KCTD006)Jiangsu Marine Structure Service Performance Improvement Engineering Research CenterKey Laboratory of Jiangsu"Marine Floating Wind Power Technology and Equipment"。
文摘We investigated the effects of fly ash(FA)content on the mechanical properties of recycled aggregate concrete(RAC)and its regeneration potential under freeze and thaw(F-T)cycles.The physical properties of second-generation recycled concrete aggregates(RCA)were used to analyze the regeneration potential of RAC after F-T cycles.Scanning electron microscopy was used to study the interfacial transition zone microstructure of RAC after F-T cycles.Results showed that adding 20%FA to RAC significantly enhanced its mechanical properties and frost resistance.Before the F-T cycles,the compressive strength of RAC with 20%FA reached 48.3 MPa,exceeding research strength target of 40 MPa.A majority of second-generation RCA with FA had been verified to attain class Ⅲ,which enabled their practical application in non-structural projects such as backfill trenches and road pavement.However,the second-generation RCA with 20%FA can achieve class Ⅱ,making it ideal for 40 MPa structural concrete.
基金financed by the Wroclaw University of Environmental and Life Sciences(Poland)。
文摘Considering the comprehensive morphology and genesis of Podzols of the Stolowe Mountains,and the still-possible impact of frost actions and other processes related to cold climate on these soils,the main aims of this study were to determine whether(i)the heterogeneous Podzols in the Stolowe Mountains underwent a phase of development in a cold climate,resulting in frost action features visible on the micromorphological level,and whether(ii)contemporary cryopedogenic traces are masked by the translocation of organic matter due to the podzolisation process.Four soil profiles were investigated,revealing distinct layers corresponding to different periods of soil formation.Under field observation,no explicit frost-related characteristics were observed.Nevertheless,micromorphological analysis revealed cappings of fine materials on grains or peds,as well as development of granostriated(or any striated)b-fabric that resulted from the alternating effects of thawing and freezing processes.Moreover,micromorphological analysis revealed the presence of microstructures that could be the result of cryogenic processes,such as platy,angular blocky and lenticular features,as well as plane,vugh and star-shaped void types.The translocation of organic matter during podzolisation modified or concealed the frost-related features that developed during the late Pleistocene and early Holocene.This is evident,for instance,in the accumulation of organic matter on cappings and within soil voids,which further hinders the identification of frost-related characteristics and the interpretation of the soil's evolution.Macromorphological observations enhanced with micromorphological analyses revealed three distinct layers:(i)a young upper layer composed of loose,sandy material;(ii)a deeper layer containing a spodic horizon with frost actions,involving pedofeatures associated with the Pleistocene cold climate and(iii)a deeper subsoil basal layer.The abovementioned microstructures,combined with lithological discontinuity,support the hypothesised polygenetic origin of Podzols in the studied region.
基金supported by National Key R&D Program of China(Grant No.2022YFB2603301)the National Natural Science Foundation of China(Grant No.52178376)Science and Technology Research and Development Program of China Railway Group Limited(Grant No.2023-Major Project-04).
文摘In cold regions,the frost-heave of soil can cause uneven railway subgrades,affecting the safety and efficiency of high-speed railways.This study proposes a novel PCW-iTransformer model for predicting frost heave,which integrates PCHIP data interpolation,CEEMDAN signal decomposition,and WPT denoising to extract sequential features.Compared to existing models like Autoformer,Crossformer,and DLinear,PCW-iTransformer achieves a reduction of 19.1%-34.5%in error metrics and an improvement of 2.8%-4.6%in the coefficient of determination.Additionally,a fused parameter model based on normalized moisture and temperature improves prediction accuracy,reducing MSE,MAE,and RMSE by up to 7.6%.The model also demonstrates robustness under data scarcity,maintaining stable performance with 40%continuous or 60%random missing data.Overall,PCW-iTransformer provides a reliable approach for predicting frost heave,offering valuable insights for the maintaining and long-term stability of high-speed railway subgrades in cold regions.
基金supported by the Shandong Provincial Natural Science Foundation(ZR2023QE325).
文摘Frost accumulation on the evaporator fins of air source heat pumps(ASHPs)severely degrades heat transfer performance and overall system efficiency.To address this,the present study employs computational fluid dynamics(CFD)to investigate how fin spacing influences frosting behavior,emphasizing the coupled evolution of frost thickness,density,airflow,and temperature distribution within fin channels.Results reveal that fin spacing is a key parameter governing both the extent and rate of frost growth.Wider fin spacing enhances frost accumulation,with a final frost mass of 6.41 g at 12 mm,about 71.8%higher than at 4 mm.In contrast,narrower spacing suppresses frost formation by accelerating airflow.The frost layer exhibits a distinct two-stage growth pattern:at 12 mm spacing,the early-stage average thickness growth rate reaches 0.021 mm/min,nearly 4.3 times that at 4 mm.Frost density follows similar initial trends across different spacings but diverges later due to thermal resistance and airflow variations.
基金funding support from the National Natural Science Foundation of China(Grants Nos.42330708 and 42302329)the Graduate Innovation Research Program of Jilin University(Grant No.2024CX118).
文摘Uneven frost heave deformation can shorten the operational lifespan of foundation engineering.Clarifying the mechanisms of uneven frost heave facilitates the targeted mitigation of frost damage.This study focused on a water conveyance channel in Jilin Province,northern China,and found after monitoring that the frost heave at the channel bottom lining exceeded that at the crest by 44.5 mm,with the freezing temperature at the bottom being over 2℃lower than that at the crest.Soil columns with an initial gravimetric moisture content of 12%,16%,18%,and 20%were then prepared.The effects of temperature and moisture content on frost heave were analyzed under two freezing conditions(-5℃and-10℃)through unidirectional freezing tests.A coupled thermo-hydro-mechanical(THM)frost heave model,validated by the test results,was further established.In the soil with an initial moisture content of 20%,the formation of ice lenses associated with substantial water migration contributed to a large temperature gradient,which can jointly induce frost heave.Under the-10℃condition,the temperature gradient in the soil column with a 20%initial moisture content reached 0.84℃/cm,the total water migration reached 10.72%,and the frost heave deformation was 1.86 mm.The THM coupling results indicated that,under the interaction of a large temperature gradient and moisture accumulation,the volumetric ice content remained high in the bottom soil during freezing and peaked at 0.36.The frost damage to the bottom soil was severe,and the maximum deformation reached 57 mm.
文摘One reference in the original manuscript contained incorrect bibliographic information and cited a non-existent publication:Traczyk A(1999)Pleistocene debris cover beds and block-debris tongues in the north-western part of theŚlęża Massif(Poland)and their formation under permafrost conditions.Geographia Polonica 81(1).This erroneous reference has now been removed from the references list.
基金supported by the Natural Sciences and Engineering Research Council of Canada(Grant Nos.Discovery 341275,and CRDPJ 543894-19)NSERC/Energi Simulation Industrial Research Chair programState Key Laboratory of Geohazard Prevention and Geoenvironment Protection Open Fund(Grant No.SKLGP2024K001).
文摘Frost heave in water-bearing rock masses poses significant threats to geotechnical engineering.This paper developed a novel three-dimensional(3D)frost model,based on the combined finite-discrete element method(FDEM),to investigate the frost heave process in rock masses where thermal transfer,water migration,water-ice phase transition(ice growth)and ice-rock interaction are explicitly simulated.The proposed model is first validated against existing experimental and analytical solutions,and further applied to investigate path-dependent frost heave behavior under various freezing conditions.Results show that freezing direction plays a vital role in the dynamic ice growth and ice-rock interaction,thus affecting the frost heave behavior.In the top-down freezing regime,ice plugs form first at the crack's top surface,sealing the crack and preventing water migration,which can amplify ice pressure.Parametric studies,including rock Young's modulus,ice-rock friction,and rock hydraulic conductivity,further reveal that the temporal aspects of ice development and rock mechanical response strongly affect ice-rock interaction and hence the frost heave mechanism.Furthermore,some typical phenomena(e.g.water/ice extrusion and frost cracking)can also be well captured in this model.This novel numerical framework sheds new light on frost heave behavior and enriches our understanding of frost heave mechanisms and ice-rock interaction processes within cold environment engineering projects.
基金supported by the National Natural Science Foundation of China(No.51808128)the Natural Science Foundation of Fujian Province(No.2022J01091)。
文摘Frost heave in seasonally frozen regions is a one-dimensional process that could severely damage infrastructure subgrades.Stress state,temperature and water migration are important factors for frost heave.This work investigated the effects of soil temperature and volumetric water content on the transient frost heave ratio during the freezing of saturated silty clay in an open system and analyzed the relationships between the transient frost heave ratio and freezing rate and between temperature gradient and frost heave rate.The results show that the frost heave ratio,frost heave rate,and freezing rate are positively correlated with the temperature gradient since the temperature gradient drives the water migration during freezing,indicating the transient temperature gradient could be used to evaluate the frost heave of saturated silty clay.The transient freezing rate and transient frost heave ratio are logarithmically related to the transient frost heave ratio and transient temperature gradient,respectively.The effects of transient temperature gradient on frost heave are the principal mechanism responsible for different frost heave characteristics and uneven frost heave along a subgrade of the same soil type.
基金the National Mission on Himalayan Studies(NMHS),Ministry of Environment,Forest and Climate Change(MoEFCC)for the financial support under the research project number(GBPNI/NMHS-2019-20/MG)。
文摘Climate change differentially influences the frozen ground,a major dynamic component of the cryosphere,on a local and regional scale.Under the warming climate with pronounced effects reported at higher altitudes,the characterization of the frozen ground is very important in the Upper Indus Basin(UIB),an important and critical region with respect to climate and hydro-glaciological dynamics.In this study,the efficiency and reliability of the surface frost number model are assessed in delineating the spatial extent of different classes of frozen ground in the region.The daily MODIS land surface temperature(LST)with ground surface temperature(GST)and surface geomorphological expressions as ground validation datasets are used jointly in efficiently determining the extent of different classes of frozen ground(continuous and discontinuous permafrost and seasonal frost).The LST and GST resonate with each other in the annual cycle of temperature variation,however,with mean annual LST exhibiting an offset(cold bias)of 5 to 7℃relative to mean GST.This study shows that the highest permafrost extent is observed in areas where the lowest thinning rates of glacier ice are reported and vice versa.The surface frost number model categorizes an area of 38%±3%and 15%±3%in the UIB as permafrost and seasonal frost,respectively.Based on the altitude model,the lower limit of alpine permafrost is approximated at a mean altitude of 4919±590 m a.s.l.in the UIB.The present study acts as preliminary work in the data sparse and inaccessible regions of the UIB in characterizing the frozen and unfrozen ground and may act as a promising input data source in glaciohydro-meteorological models for the Himalaya and Karakoram.In addition,the study also underlines the consideration of this derelict cryospheric climatic variable in defining and accounting for the sustainable development of socio-economic systems through its intricate ramification on agricultural activity,landscape stability and infrastructure.
文摘The frost growth on cold surfaces in evaporators is an undesirable phenomenon which becomes a problem for the thermal efficiency of the refrigeration systems because the ice layer acts as a thermal insulation,drastically reducing the rate of heat transfer in the system.Its accumulation implies an increase in energy demand and a decrease in the performance of various components involved in the refrigeration process,reducing its efficiency and making it necessary to periodically remove the frost,resulting in expenses for the defrost process.In the present work,a numerical-experimental analysis was performed in order to understand the formation process of porous ice in flat plates with different surface treatments and parameters.This understanding is of utmost importance to minimize the formation of porous ice on cold surfaces and improve equipment efficiency and performance.In this context,a low-cost experimental apparatus was developed,enabling an experimental analysis of the phenomenon under study.The environmental conditions evaluated are the temperature of the cold surface,roomtemperature,humidity,and air velocity.The material of the surfaces under study are aluminum,copper,and brass with different surface finishes,designated as smooth,grooved(hydrophilic),and varnished(hydrophobic).The numerical-experimental analysis demonstrates measurements and simulations of the thickness,surface temperature,and growth rate of the porous ice layer as a function of the elapsed time.The numerical results were in good agreement with the experimental results,indicating that the varnished surface,with hydrophobic characteristics,presents greater difficulty in providing the phenomenon.Therefore,the results showed that application of a coating allowed a significant reduction on the frost formation process contributing to the improvement of thermal efficiency and performance of refrigeration systems.
基金Supported by National Science and Technology Support Program(2008BADB8B01,2007BAD30B02,2007BAD30B05)Modern Agricultural Technology System Special Fund Project(nycytx-024-01-03)Guangxi Scientific and Technological Project(0782004-2,0782004-5)~~
文摘[Objective]The aim was to understand the change characteristics of sugarcane traits and evaluate the cold tolerance of sugarcane varieties under the drought and frost conditions.[Method] The experiment was carried out in Ziyuan County,Guangxi Province where the frost occurred often with 21 domestic and abroad sugarcane varieties（elites）.[Result] There were significant changes in the brix,green leaf number and photosynthetic rate of sugarcane before and after light frost and decreased more in cold-sensitive varieties.However,the correlation was only significant between the damage rate of stem length and internode,percentage of green leaves after heavy frost in relation to sugarcane brix and brix changes after light frost.Further analysis showed that the evaluation for cold tolerance of sugarcane would be more simple and reliable with traits of the damage rate of stem length and percentage of upper green leaves.The evaluation for varieties indicated that if it was not carried out for cold-tolerance identification in breeding program,the percentage of sugarcane varieties with good cold-tolerance will be lower than30%,and higher than 60% with poor cold-tolerance in subtropical and tropical regions.[Conclusion] This study had provided theoretical basis for the cold-resistant evaluation of sugar cane and the breeding of the varieties of cold-resistant.
基金Key Project of National Natural Science Foundation of China,No.41030101 National Basic Research Program of China,No.2012CB955304+1 种基金 National Natural Science Foundation of China,No.41171043 ＂Strategic Priority Research Program-Climate Change：Carbon Budget and Relevant Issues＂of the Chinese Academy of Sciences,No.XDA05090301
文摘The temperate monsoon area of China is an important agricultural region but late spring frosts have frequently caused significant damage to plants there. Based on phenological data derived from the Chinese Phenological Observation Network （CPON）, corresponding meteorological data from 12 study sites and phenological modeling, changes in flowering times of multiple woody plants and the frequency of frost occurrence were analyzed. Through these analyses, frost risk during the flowering period at each site was estimated. Results of these estimates suggested that first flowering dates （FFD） in the study area advanced significantly from 1963 to 2009 at an average rate of -1.52 days/decade in North-east China （P〈0.01） and -2.22 days/decade （P〈0.01） in North China. Over the same period, the number of frost days in spring decreased and the last frost days advanced across the study area. Considering both flowering phenology and occurrence of frost, the frost risk index, which measures the percentage of species exposed to frost during the flowering period in spring, exhibited a decreasing trend of -0.37% per decade （insignificant） in Northeast China and -1.80% per decade （P〈0.01） in North China, implying that frost risk has reduced over the past half century. These conclusions provide important information to agriculture and forest managers in devising frost protection schemes in the region.
文摘Automated over-tree sprinkler irrigation systems were developed and tested in two orchards located in two separate locations in southern Iran （a 0.17 ha peach orchard and a 0.24 ha orange orchard） to protect peach blossoms and orange trees leaves and fruits from low temperature damage. The experiment used a system that monitored the trees and air temperatures using two thermistors. The water application rate by the irrigation system was determined by an energy balance as implemented by the software FROSTPRO, In the peach orchard, the system was tested during three frost events during the spring of 2003 and three other events during the spring of 2004. The system successfully kept peach flowers above the critical temperature, i.e., -4.0℃ in spring 2004 （control block -4.12℃, and sprinkled block ＋0.5℃） during all events. Similar results were obtained in the orange orchard during three frost events in the winter of 2004, during which the tree temperatures were at least 2.5℃ above the critical temperature. Results from field tests show that the system can effectively protect the peach blossoms from damage. Determination done after the frost events showed a 12% blossom kill in the sprinkled blocks while in the unsprinkled control block a 41.5% blossom kill. Calculations indicated that when using variable application rates, the amount of water used can be reduced by 54.3%. Spatial distribution of minimum temperatures during the three frosts was also studied in Jahrom, Iran. Results showed a significant temperature control in the experimental block, especially in the central part of the orchard, but the block margins （about 3.6% of the total area） were at the risk of low temperature due to the wind drift effects.
文摘Ground temperatures from four of the seven extensively studied highway cross-sections near Gulkana/Glennallen,Alaska during 1954;962,were chosen to better understand the impacts of highway construction on warm permafrost.Both the thawing of permafrost and seasonal frost action impacted on road surface stability for about 6 years until the maximum summer thaw reached about 3 m in depth.Seasonal frost action caused most of the ensuing stability problems.Unusually warm summers and the lengths of time required to re-freeze the active layer were far more important than the average annual air temperatures in determining the temperatures of the underlying shallow permafrost,or the development of taliks.The hypothesized climate warming would slightly and gradually deepen the active layer and the developed under-lying talik,but its effect would be obscured by unusually warm summers,by warmer than usual winters,and by the vari-able lengths of time of the zero curtains.At least one period of climate mini-cooling in the deeper permafrost during the early 20th century was noted.
