Grain mildew is a significant hazard that causes food loss and poses a serious threat to human health when severe.Therefore,effective prediction and determination of mildew grade is essential for the prevention and co...Grain mildew is a significant hazard that causes food loss and poses a serious threat to human health when severe.Therefore,effective prediction and determination of mildew grade is essential for the prevention and control of mildew and global food security.In the present study,a model for predicting and determining the mildew grade of rice was constructed using logistic regression,back propagation neural network and GS-SVM(a grid search-based support vector machine algorithm)based on laboratory culture data and actual data from a granary,respectively.The results show that the GS-SVM model has a better prediction effect,but the model cannot automatically adjust the parameters and is more subjective,and the accuracy may decrease when the data set changes.Therefore,this paper establishes a new model for a support vector machine based on a fruit fly optimization algorithm(FOA-SVM),which can achieve automatic parameter search and automatically adjust its parameters to find the best result when the data set changes,with a strong ability of self-adjustment of parameters.In addition,the FOA-SVM converges quickly and the model is stable.The results of this study provide a technical method for early identification of mildew grade during grain storage,which is beneficial for the prevention and control of rice mildew during grain storage.展开更多
Now in the process of social development, people's awareness of environmental protection and health has been widely enhanced, and the use of chemical agents will be more strictly restricted. Therefore, according t...Now in the process of social development, people's awareness of environmental protection and health has been widely enhanced, and the use of chemical agents will be more strictly restricted. Therefore, according to the actual situation of grain storage, scientific, reasonable, environmental protection and healthy green grain storage technology should be adopted to ensure the safety of the stored grain and meet the goal of green and pollution-free. In the process of grain storage, some pests may be produced, which will have a corresponding impact on the storage effect of grain. This paper discusses the green control technology of stored grain pests, and analyzes the main development direction of stored grain in China in the future period of time, hoping to effectively improve the control level of pests to a certain extent, and smoothly reduce the use of some chemicals in the process of grain storage, so as to ensure the safety of people's use.展开更多
Tibetan kefir grains(TKG)serve as a unique natural starter for producing functional fermented milk(TK).However,the microbial community restructuring from solid grains to liquid milk and the associated metabolic altera...Tibetan kefir grains(TKG)serve as a unique natural starter for producing functional fermented milk(TK).However,the microbial community restructuring from solid grains to liquid milk and the associated metabolic alterations of the milk matrix remain insufficiently characterized.Here,we combined high-throughput amplicon sequencing with untargeted metabolomics to elucidate the biological and chemical transformations during fermentation.Microbiological analysis revealed a profound community shift driven by niche differentiation.While TKG was structurally dominated by Lactobacillus kefiranofaciens and Kazachstania turicensis,the fermented TK exhibited significantly higher diversity,characterized by the proliferation of opportunistic species such as Lentilactobacillus kefiri,Kluyveromyces marxianus,and notably,the emergence of Rhodococcus erythropolis.Metabolomic analysis identified 69 differential non-volatile metabolites,indicating extensive proteolysis and lipid remodeling during fermentation.Bioactive peptides,free amino acids,and tryptophan-derived indole compounds were substantially enriched,whereas lipid metabolism shifted from lysophospholipid degradation toward the accumulation of structural phospholipid,suggesting increased microbial biomass formation.These findings provide comprehensive insights into the ecological dynamics and functional metabolic landscape of TK,offering a theoretical basis for the screening of indigenous probiotics and the future exploration of functional dairy products.展开更多
Knowing the time extension degree of full mortality in phosphine fumigation at low temperature significantly contributes to successful insect pest control,especially for reducing fumigation failure and inhibiting resi...Knowing the time extension degree of full mortality in phosphine fumigation at low temperature significantly contributes to successful insect pest control,especially for reducing fumigation failure and inhibiting resistance development.The comparison ofmortality and lethal time on eggs,larvae,pupae and adults of Cryptolestes ferrugineus(Stephens)was conducted,and the strain with 1043 times of resistance factor to phosphine was assayed during fumigation with 300 mL/m^3 of phosphine concentration at 18,23 and 28℃.The LT50 values to eggs,larvae,pupae and adults of C.ferrugineus at 18℃ were postponed by 2,2,1 and 5 d comparedwith that at 23℃,and 5,4,5 and 7 d compared with that at 28℃,respectively.The LT99 values to eggs,larvae,pupae and adults at 18℃ were 5,1,2 and 7 d longer than that at 23℃,and 6,5,5 and 10 d longer than that at 28℃,respectively.The lethal time of different life stages of the C.ferrugineus strain significantly increased with temperature decreasing.The exposure time of full mortality on pupae at 300 mL/m^3 of phosphine at 18℃ reached 38 d,which was 12 d longer than that of larvae.The order of tolerance of different life stages of C.ferrugineus exposed to 300 mL/m^3 phosphine from high to low was pupae,eggs,adults,larvae at tested temperatures.展开更多
Knowing the developmental states of stored grain insects, especially for the immature stages hidden in cereal kernel, such as Sitophilus zeamais, could be in favor of monitoring early and controlling effectively. Atla...Knowing the developmental states of stored grain insects, especially for the immature stages hidden in cereal kernel, such as Sitophilus zeamais, could be in favor of monitoring early and controlling effectively. Atlas and scale parameters on different developmental stages of S. zeamais in wheat kernel were captured and described by three-dimensional microscope of super depth of field observation. The four instars of larva, pre-pupa, pupa, new adult, old adult in kernel could be seen by dissecting the infested kernels. The length, height, and width of larva body increased with insect development and centralized the sizes corresponding to the four instars of larva. The length of larva body centralized near 554, 746, 1 462, and 2 147 μm. The height of larva body centralized about 388, 575, 847, and 1 651 μm. The width of larva body centralized near 340, 598, 798, and 1 568 μm. Head capsule width was in same size for each exuviating period, centralized near 203, 317, 535, and 603 μm, and got big sharply with the instar changed. Developmental duration of four larva instars was about 21 days reared in wheat, less than 28 days reared in maize as published. The atlas and description should be helpful for monitoring the S. zeamais development hidden in cereal kernels and designing control strategy.展开更多
The attractiveness of Cinnamomum camphora(Laurales: Lauraceae) blocks and essential oil to Lasioderma serricorne(Fabricius)(Coleoptera: Anobiidae) adults was investigated. The results showed that the behavioral respon...The attractiveness of Cinnamomum camphora(Laurales: Lauraceae) blocks and essential oil to Lasioderma serricorne(Fabricius)(Coleoptera: Anobiidae) adults was investigated. The results showed that the behavioral response values of L. serricorne adults to C. camphora blocks significantly increased with increasing doses above the dose of 0.8 g. The highest behavioral response values of L. serricorne adults were 93.33% to C. camphora blocks and 81.67% to C. camphora essential oil, respectively. C. camphora blocks had stronger attractiveness to L. serricorne adults than C. camphora oil. These results demonstrate that the effectiveness to control L. serricorne in practice of C. camphora blocks and C. camphora oil deserve to be further investigated.展开更多
In order to elucidate the ability of stored product insects to resist high temperature at varying temperature conditions,the influence of different heating rates on the mortality of all life stages of Tribolium castan...In order to elucidate the ability of stored product insects to resist high temperature at varying temperature conditions,the influence of different heating rates on the mortality of all life stages of Tribolium castaneum(Herbst)(Coleoptera:Tenebrionidae)was investigated.After acclimation from 28 to 42,44 and 46℃ at different heating rates(0,1.25,2.50,5.00,and 10.00℃/h),eggs,larvae,pupae,and adults of T.castaneum were exposed at 50℃ for 0(as a control),10,15,20,25 and 30 min,respectively.The corrected mortality of T.castaneum was determined after 24 h.The results showed that different exposure times and heating rates had significant effects on the mortality of T.castaneum.The mortality of all life stages of T.castaneum with the same acclimation experience increased significantly with the increasing exposure time,and acclimation improved the heat tolerance of T.castaneum.The mortalities exposed at 50℃ for 30 min of T.castaneum eggs(acclimated to 46℃ at 5.00℃/h),larvae(acclimated to 44℃ at 2.50℃/h),pupae(acclimated to 46℃ at 5.00℃/h),and adults(acclimated to 46℃ at 2.50℃/h)were 62.50%,54.44%,58.89%and 53.33%,respectively,significantly lower than that of corresponding life stages of T.castaneum acclimated at 1.25 and 10.00℃/h.The present results are in favor of developing an effective heat treatment protocol for pest control.展开更多
Computer-aid molecular docking is a simulative process that receptors and ligands recognize each other through energy matching and geometric matching. It is widely used in bioactive compounds simulative screening and ...Computer-aid molecular docking is a simulative process that receptors and ligands recognize each other through energy matching and geometric matching. It is widely used in bioactive compounds simulative screening and preliminary exploring the bioactivity and toxicity of molecular, which plays an important guiding role in toxicity and bioactivity study of molecular entities. In our study, we used the computer-aid molecular docking software-discovery studio 3.1 client to test the mechanism of aflatoxins such as aflatoxin B1, B2, M1, M2, G1, G2 and the results of our experiment help to illustrate the pathway of aflatoxin’s toxication. We also used this technology to test the preliminary toxicity of zearalenone (ZEN) and its two degradation products:α-zearalenol (α-ZOL) and β-zearalenol (β-ZOL), which indicates that these three products possessed significant estrogenic activity. The order of the estrogenic activity is:α-zearalenol > zearalenone >β-zearalenol.展开更多
This study improved protein glutaminase(PG)yield from Chryseobacterium proteolyticum using a response surface methodology-artificial neural network-genetic algorithm(RSM-ANN-GA)strategy.Optimization of nitrogen source...This study improved protein glutaminase(PG)yield from Chryseobacterium proteolyticum using a response surface methodology-artificial neural network-genetic algorithm(RSM-ANN-GA)strategy.Optimization of nitrogen sources increased PG activity by 63.370%to 7.590 U/mL,the highest reported under shake-flask conditions.PG was applied to deamidate deacetylated soybean meal protein(DSMP),and spray drying was optimized to achieve a 29.710%powder yield.PG treatment significantly enhanced DSMP solubility,dispersibility,antioxidant capacity,and in vitro digestibility.At a deamidation degree(DD)of 55%,digestibility matched commercial soybean protein powder(CSPP),with improved umami and reduced bitterness/astringency.Color analysis showed increased brightness and lower total color difference with rising DD,while proximate and amino acid composition remained largely unchanged,preserving essential nutrients.Electronic nose and tongue profiling confirmed improved aroma and flavor through beneficial volatile compounds.These findings demonstrate that PG deamidation alleviates spray drying-induced protein aggregation while enhancing the nutritional,functional,sensory,and visual qualities of plant protein powders,offering a scalable,cost-effective approach for food industry applications.展开更多
In order to explore the effects of different pretreatments on the pore structure of Chinese yam during Microwave Freeze Drying(MFD),the samples were treated by typical drying pretreatments including osmosis,blanching ...In order to explore the effects of different pretreatments on the pore structure of Chinese yam during Microwave Freeze Drying(MFD),the samples were treated by typical drying pretreatments including osmosis,blanching and ultrasound,and compared with the untreated samples.The results showed that the pretreatment had significant impacts on the porosity of MFD Chinese yam.Ultrasonic pretreatment could obtain the highest open porosity,and the internal pore network structure of the material showed a uniform sponge shape.The shape of pores obtained by blanching pretreatment was the most irregular.The pore network structure obtained by different pretreatments could result in various product texture and rehydration,which implied that pretreatment methods should be carefully selected according to actual requirements.All these pretreatments could improve the open porosity of MFD Chinese yam,which result in a better rehydration capability.Among them,ultrasonic treatment is worth further investigating.展开更多
Slope variation will significantly affect the characteristics of the wind field around a hill.This paper conducts a large-eddy simulation(LES)on an ideal 3D hill to study the impact of slope on wind field properties.E...Slope variation will significantly affect the characteristics of the wind field around a hill.This paper conducts a large-eddy simulation(LES)on an ideal 3D hill to study the impact of slope on wind field properties.Eight slopes ranging from 10°to 45°at 5°intervals are considered,which covers most conventional hill slopes.The inflow turbulence for the LES is generated by adopting a modified generation method that combines the equilibrium boundary conditions with the Fluent inherent vortex method to improve the simulation accuracy.The time-averaged flow field and the instantaneous vortex structure under the eight slopes are comparatively analyzed.The accuracy of the present method is verified by comparison with experimental data.The slope can affect both the mean and fluctuating wind flow fields around the 3D hill,especially on the hilltop and the leeward side,where a critical slope of 25°can be observed.The fluctuating wind speeds at the tops of steep hills(with slope angles beyond 25°)decrease with increasing slope,while the opposite phenomenon occurs on gentle hills.With increasing slope,the energy of the high-speed descending airflow is enhanced and pushes the separated flow closer to the hill surface,resulting in increased wind speed near the wall boundary on the leeward side and inhibiting the development of turbulence.The vortex shedding trajectory in the wake region becomes wider and longer,suppressing the growth of the mean wind near the wall boundary and enhancing the turbulence intensity.展开更多
基金the Special Funds for National Key Research and Development Program of China(No.2017YD0401005).
文摘Grain mildew is a significant hazard that causes food loss and poses a serious threat to human health when severe.Therefore,effective prediction and determination of mildew grade is essential for the prevention and control of mildew and global food security.In the present study,a model for predicting and determining the mildew grade of rice was constructed using logistic regression,back propagation neural network and GS-SVM(a grid search-based support vector machine algorithm)based on laboratory culture data and actual data from a granary,respectively.The results show that the GS-SVM model has a better prediction effect,but the model cannot automatically adjust the parameters and is more subjective,and the accuracy may decrease when the data set changes.Therefore,this paper establishes a new model for a support vector machine based on a fruit fly optimization algorithm(FOA-SVM),which can achieve automatic parameter search and automatically adjust its parameters to find the best result when the data set changes,with a strong ability of self-adjustment of parameters.In addition,the FOA-SVM converges quickly and the model is stable.The results of this study provide a technical method for early identification of mildew grade during grain storage,which is beneficial for the prevention and control of rice mildew during grain storage.
文摘Now in the process of social development, people's awareness of environmental protection and health has been widely enhanced, and the use of chemical agents will be more strictly restricted. Therefore, according to the actual situation of grain storage, scientific, reasonable, environmental protection and healthy green grain storage technology should be adopted to ensure the safety of the stored grain and meet the goal of green and pollution-free. In the process of grain storage, some pests may be produced, which will have a corresponding impact on the storage effect of grain. This paper discusses the green control technology of stored grain pests, and analyzes the main development direction of stored grain in China in the future period of time, hoping to effectively improve the control level of pests to a certain extent, and smoothly reduce the use of some chemicals in the process of grain storage, so as to ensure the safety of people's use.
基金supported by the National Natural Science Foundation of China(32502227)the Natural Science Foundation of Henan Province(252300421650)the Key Scientific Research Project of Colleges and Universities in Henan Province(26A550016).
文摘Tibetan kefir grains(TKG)serve as a unique natural starter for producing functional fermented milk(TK).However,the microbial community restructuring from solid grains to liquid milk and the associated metabolic alterations of the milk matrix remain insufficiently characterized.Here,we combined high-throughput amplicon sequencing with untargeted metabolomics to elucidate the biological and chemical transformations during fermentation.Microbiological analysis revealed a profound community shift driven by niche differentiation.While TKG was structurally dominated by Lactobacillus kefiranofaciens and Kazachstania turicensis,the fermented TK exhibited significantly higher diversity,characterized by the proliferation of opportunistic species such as Lentilactobacillus kefiri,Kluyveromyces marxianus,and notably,the emergence of Rhodococcus erythropolis.Metabolomic analysis identified 69 differential non-volatile metabolites,indicating extensive proteolysis and lipid remodeling during fermentation.Bioactive peptides,free amino acids,and tryptophan-derived indole compounds were substantially enriched,whereas lipid metabolism shifted from lysophospholipid degradation toward the accumulation of structural phospholipid,suggesting increased microbial biomass formation.These findings provide comprehensive insights into the ecological dynamics and functional metabolic landscape of TK,offering a theoretical basis for the screening of indigenous probiotics and the future exploration of functional dairy products.
基金This work was supported by National Key Research and Development Program of the 13th Five-Year Plan(No.2017YFC1600800).
文摘Knowing the time extension degree of full mortality in phosphine fumigation at low temperature significantly contributes to successful insect pest control,especially for reducing fumigation failure and inhibiting resistance development.The comparison ofmortality and lethal time on eggs,larvae,pupae and adults of Cryptolestes ferrugineus(Stephens)was conducted,and the strain with 1043 times of resistance factor to phosphine was assayed during fumigation with 300 mL/m^3 of phosphine concentration at 18,23 and 28℃.The LT50 values to eggs,larvae,pupae and adults of C.ferrugineus at 18℃ were postponed by 2,2,1 and 5 d comparedwith that at 23℃,and 5,4,5 and 7 d compared with that at 28℃,respectively.The LT99 values to eggs,larvae,pupae and adults at 18℃ were 5,1,2 and 7 d longer than that at 23℃,and 6,5,5 and 10 d longer than that at 28℃,respectively.The lethal time of different life stages of the C.ferrugineus strain significantly increased with temperature decreasing.The exposure time of full mortality on pupae at 300 mL/m^3 of phosphine at 18℃ reached 38 d,which was 12 d longer than that of larvae.The order of tolerance of different life stages of C.ferrugineus exposed to 300 mL/m^3 phosphine from high to low was pupae,eggs,adults,larvae at tested temperatures.
基金Supported by National Keypoint Research and Invention Program of the Thirteenth(2017YFC1600804)
文摘Knowing the developmental states of stored grain insects, especially for the immature stages hidden in cereal kernel, such as Sitophilus zeamais, could be in favor of monitoring early and controlling effectively. Atlas and scale parameters on different developmental stages of S. zeamais in wheat kernel were captured and described by three-dimensional microscope of super depth of field observation. The four instars of larva, pre-pupa, pupa, new adult, old adult in kernel could be seen by dissecting the infested kernels. The length, height, and width of larva body increased with insect development and centralized the sizes corresponding to the four instars of larva. The length of larva body centralized near 554, 746, 1 462, and 2 147 μm. The height of larva body centralized about 388, 575, 847, and 1 651 μm. The width of larva body centralized near 340, 598, 798, and 1 568 μm. Head capsule width was in same size for each exuviating period, centralized near 203, 317, 535, and 603 μm, and got big sharply with the instar changed. Developmental duration of four larva instars was about 21 days reared in wheat, less than 28 days reared in maize as published. The atlas and description should be helpful for monitoring the S. zeamais development hidden in cereal kernels and designing control strategy.
基金Supported by National Program on Key R&D Project(No.2017YFC1600804)Key Technologies R&D Program of the Education Department of Henan Province(No.16A210017)Province Key Laboratory of Transformation and Utilization of Cereal Resource,Henan University of Technology
文摘The attractiveness of Cinnamomum camphora(Laurales: Lauraceae) blocks and essential oil to Lasioderma serricorne(Fabricius)(Coleoptera: Anobiidae) adults was investigated. The results showed that the behavioral response values of L. serricorne adults to C. camphora blocks significantly increased with increasing doses above the dose of 0.8 g. The highest behavioral response values of L. serricorne adults were 93.33% to C. camphora blocks and 81.67% to C. camphora essential oil, respectively. C. camphora blocks had stronger attractiveness to L. serricorne adults than C. camphora oil. These results demonstrate that the effectiveness to control L. serricorne in practice of C. camphora blocks and C. camphora oil deserve to be further investigated.
基金supported by National Natural Science Foundation of China(No.U1604115)Henan Provincial Key Scientific and Technological R&D Project(No.182102110111)。
文摘In order to elucidate the ability of stored product insects to resist high temperature at varying temperature conditions,the influence of different heating rates on the mortality of all life stages of Tribolium castaneum(Herbst)(Coleoptera:Tenebrionidae)was investigated.After acclimation from 28 to 42,44 and 46℃ at different heating rates(0,1.25,2.50,5.00,and 10.00℃/h),eggs,larvae,pupae,and adults of T.castaneum were exposed at 50℃ for 0(as a control),10,15,20,25 and 30 min,respectively.The corrected mortality of T.castaneum was determined after 24 h.The results showed that different exposure times and heating rates had significant effects on the mortality of T.castaneum.The mortality of all life stages of T.castaneum with the same acclimation experience increased significantly with the increasing exposure time,and acclimation improved the heat tolerance of T.castaneum.The mortalities exposed at 50℃ for 30 min of T.castaneum eggs(acclimated to 46℃ at 5.00℃/h),larvae(acclimated to 44℃ at 2.50℃/h),pupae(acclimated to 46℃ at 5.00℃/h),and adults(acclimated to 46℃ at 2.50℃/h)were 62.50%,54.44%,58.89%and 53.33%,respectively,significantly lower than that of corresponding life stages of T.castaneum acclimated at 1.25 and 10.00℃/h.The present results are in favor of developing an effective heat treatment protocol for pest control.
文摘Computer-aid molecular docking is a simulative process that receptors and ligands recognize each other through energy matching and geometric matching. It is widely used in bioactive compounds simulative screening and preliminary exploring the bioactivity and toxicity of molecular, which plays an important guiding role in toxicity and bioactivity study of molecular entities. In our study, we used the computer-aid molecular docking software-discovery studio 3.1 client to test the mechanism of aflatoxins such as aflatoxin B1, B2, M1, M2, G1, G2 and the results of our experiment help to illustrate the pathway of aflatoxin’s toxication. We also used this technology to test the preliminary toxicity of zearalenone (ZEN) and its two degradation products:α-zearalenol (α-ZOL) and β-zearalenol (β-ZOL), which indicates that these three products possessed significant estrogenic activity. The order of the estrogenic activity is:α-zearalenol > zearalenone >β-zearalenol.
基金supported by Grain Storage,Transportation,Processing and Safety Engineering Research Center,Anhui Vocational College of Grain Engineering Project(grant number ALAQ202401010).
文摘This study improved protein glutaminase(PG)yield from Chryseobacterium proteolyticum using a response surface methodology-artificial neural network-genetic algorithm(RSM-ANN-GA)strategy.Optimization of nitrogen sources increased PG activity by 63.370%to 7.590 U/mL,the highest reported under shake-flask conditions.PG was applied to deamidate deacetylated soybean meal protein(DSMP),and spray drying was optimized to achieve a 29.710%powder yield.PG treatment significantly enhanced DSMP solubility,dispersibility,antioxidant capacity,and in vitro digestibility.At a deamidation degree(DD)of 55%,digestibility matched commercial soybean protein powder(CSPP),with improved umami and reduced bitterness/astringency.Color analysis showed increased brightness and lower total color difference with rising DD,while proximate and amino acid composition remained largely unchanged,preserving essential nutrients.Electronic nose and tongue profiling confirmed improved aroma and flavor through beneficial volatile compounds.These findings demonstrate that PG deamidation alleviates spray drying-induced protein aggregation while enhancing the nutritional,functional,sensory,and visual qualities of plant protein powders,offering a scalable,cost-effective approach for food industry applications.
基金The authors acknowledge that this work was financially supported by the National Natural Science Foundation of China(Contract No.31671907 and No.31972207).
文摘In order to explore the effects of different pretreatments on the pore structure of Chinese yam during Microwave Freeze Drying(MFD),the samples were treated by typical drying pretreatments including osmosis,blanching and ultrasound,and compared with the untreated samples.The results showed that the pretreatment had significant impacts on the porosity of MFD Chinese yam.Ultrasonic pretreatment could obtain the highest open porosity,and the internal pore network structure of the material showed a uniform sponge shape.The shape of pores obtained by blanching pretreatment was the most irregular.The pore network structure obtained by different pretreatments could result in various product texture and rehydration,which implied that pretreatment methods should be carefully selected according to actual requirements.All these pretreatments could improve the open porosity of MFD Chinese yam,which result in a better rehydration capability.Among them,ultrasonic treatment is worth further investigating.
基金supported by the National Key R&D Plan of China(No.2018YFB1501104)the National Natural Science Foundation of China(Grant No.52278511)+1 种基金the Natural Science Foundation of Hebei Province(No.E2021210053)the Young Backbone Teacher Cultivation Program of Henan University of Technology.
文摘Slope variation will significantly affect the characteristics of the wind field around a hill.This paper conducts a large-eddy simulation(LES)on an ideal 3D hill to study the impact of slope on wind field properties.Eight slopes ranging from 10°to 45°at 5°intervals are considered,which covers most conventional hill slopes.The inflow turbulence for the LES is generated by adopting a modified generation method that combines the equilibrium boundary conditions with the Fluent inherent vortex method to improve the simulation accuracy.The time-averaged flow field and the instantaneous vortex structure under the eight slopes are comparatively analyzed.The accuracy of the present method is verified by comparison with experimental data.The slope can affect both the mean and fluctuating wind flow fields around the 3D hill,especially on the hilltop and the leeward side,where a critical slope of 25°can be observed.The fluctuating wind speeds at the tops of steep hills(with slope angles beyond 25°)decrease with increasing slope,while the opposite phenomenon occurs on gentle hills.With increasing slope,the energy of the high-speed descending airflow is enhanced and pushes the separated flow closer to the hill surface,resulting in increased wind speed near the wall boundary on the leeward side and inhibiting the development of turbulence.The vortex shedding trajectory in the wake region becomes wider and longer,suppressing the growth of the mean wind near the wall boundary and enhancing the turbulence intensity.
