The coupling model of major influence factors such state affecting the chloride diffusion process in concrete is as environmental relative humidity, load-induced crack and stress discussed. The probability distributio...The coupling model of major influence factors such state affecting the chloride diffusion process in concrete is as environmental relative humidity, load-induced crack and stress discussed. The probability distributions of the critical chloride concentration Cc, the chloride diffusion coefficient D, and the surface chloride concentration Cs were determined based on the collected natural exposure data. And the estimation of probability of corrosion initiation considering the coupling effects of influence factors is presented. It is found that the relative humidity and curing time are the most effective factors affecting the probability of corrosion initiation before and after 10 years of exposure time. At the same exposure time, the influence of load-induced crack and stress state on the probability of corrosion initiation is obvious, in which the effect of crack is the most one展开更多
[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore ...[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore the nonlinear response relationship between phytoplankton community structure and its driving factors in spring and autumn in Furong Creek under the construction of cascade weirs.[Methods]The structure of phytoplankton communities and related environmental factors were investigated in Furong Creek from 2023 to 2024.This study focused on the analysis of the changes of nutrient concentrations and biomass of phytoplankton in autumn and spring within the same dry season in Furong Creek.Redundancy analysis was used to identify the key factors influencing the structure of phytoplankton communities.The MIKE 11 model was employed to simulate the hydrodynamic changes in the river.Combined with total nitrogen and permanganate index,a GAM model of phytoplankton diversity index and hydrodynamic factors was developed,and the change of phytoplankton diversity after the optimized layout of the cascade weirs was fitted.[Results]The result showed that the annual average value of Shannon-Wiener diversity index of phytoplankton in Furong Creek was 2.79,which was in a state of mild pollution.A total of 239 species from 95 genera in 8 phyla were identified.Among the phytoplankton,Chlorophyta was the dominant group throughout the year in Furong Creek,followed by Bacillariophyta and Cyanophyta.The cell abundance of phytoplankton ranged from 3.11 to 20.64 mg/L and from 0.23 to 6.31 mg/L in spring and autumn,which indicated a clear seasonal succession of phytoplankton community structure.Compared with autumn,the relative abundance of Cyanophyta significantly decreased in spring across the whole river section,while Chrysophyta and Dinophyta showed significant increase at some monitoring sites,leading to water bloom phenomenon and a noticeable decline in the diversity of phytoplankton.The dominant species in the water bodies throughout the year were Cyclotella catenata,Chlorella vulgaris,Scenedesmus bijuga,Scenedesmus quadricauda,Chroomonas acuta,Cryptomonas ovata,and Cryptomonas erosa.Redundancy analysis(RDA)showed that hydrodynamic factors(v,h)and water environmental factors(TN,COD_(Mn))were the main influencing factors of phytoplankton community structure.[Conclusion]The result show that the nutrient concentration,phytoplankton biomass,and density in Furong Creek in spring are significantly higher than in autumn.The GAM model,constructed by combining hydrodynamic and environmental factors,can effectively reflect the nonlinear relationship between phytoplankton diversity index and its driving factors.In spring,with an increase in nutrient concentration,the habitat conditions of low flow speed and high water depths formed by overflow weirs will lead to a decrease in the Shannon-Wiener index of phytoplankton and an intensified risk of eutrophication.However,a reasonable layout scheme of cascade weirs will improve the diversity of phytoplankton and reduce the risk of eutrophication in the river.The findings of this study can help deepen the understanding of the ecological and environmental effects of cascade weir construction in the river.展开更多
Roof disaster has always been an important factor restricting coal mine safety production.Acidic effect can reform the rock mass structure to weaken the macroscopic strength characteristics,which is an effective way t...Roof disaster has always been an important factor restricting coal mine safety production.Acidic effect can reform the rock mass structure to weaken the macroscopic strength characteristics,which is an effective way to control the hard limestone roof.In this study,the effects of various factors on the reaction characteristics and mechanical properties of limestone were analyzed.The results show that the acid with stronger hydrogen production capacity after ionization(pK_(a)<0)has more prominent damage to the mineral grains of limestone.When pKa increases from−8.00 to 15.70,uniaxial compressive strength and elastic modulus of limestone increase by 117.22%and 75.98%.The influence of acid concentration is manifested in the dissolution behavior of mineral crystals,the crystal defects caused by large-scale acid action will lead to the deterioration of limestone strength,and the strength after 15%concentration reformation can be reduced by 59.42%.The effect of acidification time on limestone has stages and is the most obvious in the initial metathesis reaction stage(within 60 min).The key to the strength damage of acidified limestone is the participation of hydrogen ions in the reaction system.Based on the analytic hierarchy process method,the influence weights of acid type,acid concentration and acidification time on strength are 24.30%,59.54% and 16.16%,respectively.The research results provide theoretical support for the acidification control of hard limestone roofs in coal mines.展开更多
To make grain price stable is an important goal for the Chinese government. The paper compared the grain supply elasticity and demand elasticity to determine the grain price stability in China; used ＂k value＂ method...To make grain price stable is an important goal for the Chinese government. The paper compared the grain supply elasticity and demand elasticity to determine the grain price stability in China; used ＂k value＂ method to analyze the grain price fluctuation from 1985 to 2010; divided the grain price volatility into three stages; and analyzed the factors in each phase. On the base, it put forward some countermeasures to guarantee the stability of the grain price.展开更多
[Objective]The channel straightening project of the Pinglu Canal has fragmented the river course,compromising the integrity of original river course and causing ecosystem patchiness.Understanding the current status of...[Objective]The channel straightening project of the Pinglu Canal has fragmented the river course,compromising the integrity of original river course and causing ecosystem patchiness.Understanding the current status of fish resources and the characteristics of their diversity is crucial for the ecological management of the Pinglu Canal.[Methods]During the spring and autumn in 2021 and 2022,a survey of fish resources and species diversity in the Pinglu Canal was conducted using multi-mesh gill nets.A total of 125 fish species were collected,belonging to 10 orders,34 families,and 89 genera.[Results]The result showed that the Pinglu Canal contained three nationally protected Class II species,two endemic species of the Qinjiang River,three anadromous/migratory species,and eight invasive species,accounting for 2.4%,1.6%,2.4%,and 6.4%of the total species,respectively.The fish community primarily consisted of mid-and bottom-dwelling,adhesive-egg-laying,and omnivorous species.The Shannon-Wiener,Simpson,Margalef,and Pielou indices of the fish community in the Pinglu Canal ranged from 2.347 to 2.757,0.081 to 0.151,3.493 to 4.382,and 0.812 to 0.892,respectively.These indices showed relatively uniform distribution across different river reaches.[Conclusion]The result indicate that the fish community structure in the Pinglu Canal is relatively uniform.The reach from the Yujiang River to the Shaping River shows higher stability,while other river reaches experience moderate or severe disturbances.This study provides supplementary baseline data on the fish community structure in the Pinglu Canal and explores the potential impact of inter-basin connectivity on fish resources,aiming to provide a scientific basis for habitat restoration assessments after the channel straightening project.展开更多
Due to the presence of nitro groups, the dust generated during the production and utilization of energetic materials may potentially lead to dust explosion even under low-oxygen or anaerobic conditions.Considering the...Due to the presence of nitro groups, the dust generated during the production and utilization of energetic materials may potentially lead to dust explosion even under low-oxygen or anaerobic conditions.Considering the high energy density of energetic materials, dust explosion can cause serious production safety accidents. Therefore, it is necessary to understand the dust explosion characteristics of energetic materials and the mechanism of dust explosion. According to the literature review, among various influencing factors, the physical and chemical properties of dust are the decisive factors affecting the explosion characteristics of dust. In addition to experimental studies, numerical simulation is another important tool. However, it is subjected to certain limitations. Moreover, it is essential but challenging to fully understand the underlying mechanism. In addition, given the safety hazards posed by dust explosion, explosion suppression has attracted extensive attention for research. Depending on the medium used, there are different forms of suppression, including powder explosion suppression, water spray explosion suppression, inert gas explosion suppression, porous material explosion suppression, and vacuum chamber explosion suppression. As for the selection of explosion suppression agent, consideration must be given to the characteristics of the material. Furthermore, the above research has laid a foundation for discussing the future progress in studying dust explosion of energetic materials, with nano dust and the constraints of existing technology as the focal point.展开更多
The interception probability of a single missile is the basis for combat plan design and weapon performance evaluation,while its influencing factors are complex and mutually coupled.Existing calculation methods have v...The interception probability of a single missile is the basis for combat plan design and weapon performance evaluation,while its influencing factors are complex and mutually coupled.Existing calculation methods have very limited analysis of the influence mechanism of influencing factors,and none of them has analyzed the influence of the guidance law.This paper considers the influencing factors of both the interceptor and the target more comprehensively.Interceptor parameters include speed,guidance law,guidance error,fuze error,and fragment killing ability,while target performance includes speed,maneuverability,and vulnerability.In this paper,an interception model is established,Monte Carlo simulation is carried out,and the influence mechanism of each factor is analyzed based on the model and simulation results.Finally,this paper proposes a classification-regression neural network to quickly estimate the interception probability based on the value of influencing factors.The proposed method reduces the interference of invalid interception data to valid data,so its prediction accuracy is significantly better than that of pure regression neural networks.展开更多
The mathematical and simulation models of working head in the deep-sea working environment were built to analyze the effects of cutter-suction flow,cutter-head rotating speed,cutting depth and suction port position on...The mathematical and simulation models of working head in the deep-sea working environment were built to analyze the effects of cutter-suction flow,cutter-head rotating speed,cutting depth and suction port position on the cutter-suction capacity.The efficiency of the cutter-suction is analyzed based on the analysis of the variation law of the solid-phase volume fraction of the flow field,the variation law of the velocity distribution in the flow field and the distribution law of the solid-phase concentration.The results show that the increase of cutter-suction flow can significantly improve the cutter-suction efficiency when it is less than1000m3/h.However,when it is more than1000m3/h,it is helpless.When the cutter-head rotate speed is within the range of10–25r/min,the cutter-suction efficiency stabilizes at about95%.While the speed is greater than25r/min,the cutter-suction efficiency decreases sharply with the increase of cutter-head rotate speed.With the increase of cutting depth,the cutter-suction efficiency first increases and then remains stable and finally decreases.The cutter-suction efficiency remains at about94%when the suction port position deviation ranges from0°to30°,but it has a sharply reduction when the deviation angle is more than30°.展开更多
Heilongjiang Province is an important marketable grain depot in China. Since the reform and opening up, Heilongjiang Province production capacity of foodstuff is increasingly growing into a new level. This paper start...Heilongjiang Province is an important marketable grain depot in China. Since the reform and opening up, Heilongjiang Province production capacity of foodstuff is increasingly growing into a new level. This paper started with the actuality of Heilongjiang Province integrated production capacity of foodstuff, and analyzed its major factors empirically through the mathematical model, then proposed some measures to enhance Heilongjiang Province production capacity of foodstuff which ensured China foodstuff security展开更多
The recently proposed interface propagation-based method has shown its advantages in obtaining the thermal conductivity of phase change materials during solid-liquid transition over conventional techniques. However, i...The recently proposed interface propagation-based method has shown its advantages in obtaining the thermal conductivity of phase change materials during solid-liquid transition over conventional techniques. However, in previous investigation, the analysis on the measurement error was qualitative and only focused on the total effects on the measurement without decoupling the influencing factors. This paper discusses the effects of influencing factors on the measurement results for the interface propagation-based method. Numerical simulations were performed to explore the influencing factors, namely model simplification, subcooling and natural convection, along with their impact on the measurement process and corresponding measurement results. The numerical solutions were provided in terms of moving curves of the solid-liquid interface and the predicted values of thermal conductivity. Results indicated that the impact of simplified model was strongly dependent on Stefan number of the melting process. The degree of subcooling would lead to underestimated values for thermal conductivity prediction. The natural convection would intensify the heat transfer rate in the liquid region, thereby overestimating the obtained results of thermal conductivity. Correlations and experimental guidelines are provided. The relative errors are limited in ±1.5%,±3%and ±2% corresponding to the impact of simplified model, subcooling and natural convection, respectively.展开更多
The granular dynamic shear strength is the same as that of the static one in nature, as found from numerous experiments and investigations. The shear strength is equal to the sum of the internal frictional force and t...The granular dynamic shear strength is the same as that of the static one in nature, as found from numerous experiments and investigations. The shear strength is equal to the sum of the internal frictional force and the cohesive force. The influences of type, shape, size distribution, pore ratio, moisture content and variation of vibration velocity on the dynamic shear strength of granules were studied. Based on numerous vibration shear experiments, the authors investigate the mechanism of dynamic shear strength in granules in terms of the fundamental principle and the relevant theory of modern tribology.展开更多
As a new mode to offer finance support in rural areas, the establishment of rural banks provide not only service and support for the agricultural development and rural economy, but also solutions to the issue of long-...As a new mode to offer finance support in rural areas, the establishment of rural banks provide not only service and support for the agricultural development and rural economy, but also solutions to the issue of long-standing fund shortage and poverty in China. However, there are still a lot of problems that restrict the development of rural banks, such as unreasonable property right, unsound system of management as well as rural social credit, lacking of high-quality employees, innovation, policy support, supervision system, social awareness. Therefore, the analytic hierarchy process was employed in the current study with the aim of figuring out the essential factors which restricted the development of rural banks from two aspects of internal factors and external factors, furthermore, relevant suggestions were put forward.展开更多
In order to avoid the curing effects of paraffin on the transport process and reduce the transport difficulty,usually high temperature and high pressure are used in the transportation of oil and gas.The differences of...In order to avoid the curing effects of paraffin on the transport process and reduce the transport difficulty,usually high temperature and high pressure are used in the transportation of oil and gas.The differences of temperature and pressure cause additional stress along the pipeline,due to the constraint of the foundation soil,the additional stress can not release freely,when the additional stress is large enough to motivate the submarine pipelines buckle.In this work,the energy method is introduced to deduce the analytical solution which is suitable for the global buckling modes of idealized subsea pipeline and analyze the relationship between the critical buckling temperature,buckling length and amplitude under different high-order global lateral buckling modes.To obtain a consistent formulation of the problem,the principles of virtual displacements and the variation calculus for variable matching points are applied.The finite element method based on elasto-plastic theory is used to simulate the lateral global buckling of the pipelines under high temperature and pressure.The factors influencing the lateral buckling of pipelines are further studied.Based upon some actual engineering projects,the finite element results are compared with the analytical ones,and then the influence of thermal stress,the section rigidity of pipeline,the soil properties and the trigging force to the high order lateral buckling are discussed.The method of applying the small trigging force on pipeline is reliable in global buckling numerical analysis.In practice,increasing the section rigidity of a pipeline is an effective measure to improve the ability to resist the global buckling.展开更多
In the view of the problems existing in horizontal well,such as sand depositing and cleaning difficulty of borehole,a technology with rotating jet suitable to resolution of the problems was presented.Based on liquid s...In the view of the problems existing in horizontal well,such as sand depositing and cleaning difficulty of borehole,a technology with rotating jet suitable to resolution of the problems was presented.Based on liquid solid two-phase flow theory,the analyses on the sand movement law and the swirling field influential factors were conducted.Results show that:1) With the increasing of displacement in horizontal section annulus,swirling field strength increases,and when the displacement is constant,the closer from the nozzle,the stronger the swirling field strength is;2) Head rotating speed and liquid viscosity have little influence on the swirling field strength,but the sand-carrying rate of fluid can increase by increasing liquid viscosity in a certain range;3) Rotating the string and reducing its eccentricity in annulus are conducive for sand migration in the annulus;4) The sand can be suspended and accelerated again and the swirling field strength is enhanced by the helix agitator.Hence,the research results provide the theoretical basis for the design and application of rotating jet tool.展开更多
The study was motivated by the fact that explosion inside the subway structure may not only cause direct life loss,but also damage the subway structure and lead to further loss of lives and properties.The propagation ...The study was motivated by the fact that explosion inside the subway structure may not only cause direct life loss,but also damage the subway structure and lead to further loss of lives and properties.The propagation law of explosion wave in the subway station was analyzed and a simplified model of overpressure in the subway station was also proposed.Whereafter,the improved dynamic cam-clay model of soil and the concrete damaged plasticity constitutive model were used for the dynamic analysis of the subway station.Meanwhile,the influences of soil stiffness and burial depth on the dynamic response of the subway station were looked into.The results show that the multi-peak overpressure in the subway station does not appear,and large stresses concentrate on the central column and the floor slab of the subway station,so some special reinforcement measures should be taken in these parts.The effect of soil stiffness and burial depth on the stress of the central column is little;however,the effect on the stress of the station side wall is relatively obvious.展开更多
The Cretaceous is a typical period for studying the greenhouse climate and the earth system interactions, and the world’s most extensive terrestrial strata are mainly in East Asia, especially in China. Continental se...The Cretaceous is a typical period for studying the greenhouse climate and the earth system interactions, and the world’s most extensive terrestrial strata are mainly in East Asia, especially in China. Continental sediments can effectively reflect the paleo-climate change, but the previous studies of the Late Cretaceous paleo-climate, based on the combined characteristics of continental climate-sensitive sediments, were barely found in China. To obtain the Late Cretaceous paleo-climate characteristics of China, the distribution characteristics of different continental climate-sensitive sediment types in the early, middle and Late Cretaceous in China were studied in detail. According to the distribution and combination characteristics and types of continental climate-sensitive sediments, seven climate types can be divided: 1) warm-humid and warm-dry climate;2) hot and dry climate;3) hot-dry and arid climate;4) hot-dry and semiarid climate;5) hot-dry and hot-wet climate;6) hot-dry and warm-humid climate;7) hot-dry and warm-dry climate. The results show that in the early Late Cretaceous, the hot and dry climate was the most widespread, followed by warm-humid and warm-dry climate, but the climate was drier than the paleo-climate of the previous study of Early Cretaceous. Hot and dry climate zone became wider in the Coniacian and Maastrichtian;furthermore, it covered Xinjiang to the east of China from east to west after the Santonian Period. The hot-dry and semiarid climate zone was nearly latitudinally distributed from the northwest to the southeast and it shows a further increase in aridification. Global geological events, paleogeographic features and regional tectonic evolution had significant impacts on the paleoclimate of China in the Late Cretaceous, such as global eruptive events of volcanoes led to the temperature increase in China in the early Late Cretaceous;coastal mountain ranges in southeastern China led to the drying of the Late Cretaceous climate in southern China;Xuefeng Mountains, Wuling Mountains, Nanling Mountains and Tai-hang Mountains were the dividing line between the hot and dry climate zone and hot-dry and arid climate zone in the early Late Cretaceous, and Altun Mountains were the dividing line between the southeastern section of the hot and dry climate zone in western China in the middle Late Cretaceous.展开更多
Chinese cultural identity has great significance in maintaining the unity of Chinese nation and promo-ting the development of Chinese culture.This paper explains the definition and development of Chinese cultural iden...Chinese cultural identity has great significance in maintaining the unity of Chinese nation and promo-ting the development of Chinese culture.This paper explains the definition and development of Chinese cultural iden-tity.Research targets include Chinese cultural identity of collge students and Chinese cultural identity of Chinese eth-nic minorities.This paper also carries out a comparative research from an international perspective.Enhancing Chinese cultural identity not only has an important efect on the prosperity and development of Chinese culture,but also has far-reaching impact on the Chinese national identity.展开更多
Embankment stability is the primary problem for the expressway construction in permafrost regions.The proposed Qinghai-Tibet Expressway(QTE)is planned to construct along the Qinghai-Tibet Project Corridor.Confronted w...Embankment stability is the primary problem for the expressway construction in permafrost regions.The proposed Qinghai-Tibet Expressway(QTE)is planned to construct along the Qinghai-Tibet Project Corridor.Confronted with harsh environmental condition and intense heat exchange between earth and atmosphere,it is necessary to predict and evaluate the stability of the proposed QTE.In this study,the factors affecting the embankment stability are analyzed firstly.And then,a scheme for the stability evaluation of the embankment is established.Finally,the evaluation scheme is used for the pre-evaluation of the stability for the proposed QTE with different geothermal regulation measures(GRMs).The results indicate that the influencing factors include climatic environment,permafrost property,engineering condition and geological condition,and among them,engineering condition and permafrost property are the main influence factors for embankment stability.The stability of the proposed QTE varies greatly in the different geomorphological regions.The application effect and contribution to embankment stability of the existing GRMs are different,and using GRMs cannot completely overcome the influence of various factors on expressway stability.In the construction process,different GRMs should be adopted depending on the geomorphological environment where the embankment is located to ensure the embankment stability.展开更多
This paper elaborated dairy consumption status in Heilongjiang Province from seven aspects： dairy total consumption, comparison of dairy consumption between urban and rural, dairy consumption under different income l...This paper elaborated dairy consumption status in Heilongjiang Province from seven aspects： dairy total consumption, comparison of dairy consumption between urban and rural, dairy consumption under different income levels, consumption category structure, consumption brand structure, consumption channels and consumer information source. On this basis, factors affecting dairy consumption and trends of dairy consumption were further analyzed. The result showed that dairy consumption potential of Heilongjiang Province should be excavated. On one hand, rural consumer market should be further developed; on the other hand, dairy consumption market should be further broken down to meet different needs of different groups of people.展开更多
基金Project(50925829) supported by the National Science Fund for Distinguished Young Scholars of ChinaProject(50908148) supported by the National Natural Science Foundation of ChinaProjects(2009-K4-23,2010-11-33) supported by the Research of Ministry of Housing and Urban Rural Development of China
文摘The coupling model of major influence factors such state affecting the chloride diffusion process in concrete is as environmental relative humidity, load-induced crack and stress discussed. The probability distributions of the critical chloride concentration Cc, the chloride diffusion coefficient D, and the surface chloride concentration Cs were determined based on the collected natural exposure data. And the estimation of probability of corrosion initiation considering the coupling effects of influence factors is presented. It is found that the relative humidity and curing time are the most effective factors affecting the probability of corrosion initiation before and after 10 years of exposure time. At the same exposure time, the influence of load-induced crack and stress state on the probability of corrosion initiation is obvious, in which the effect of crack is the most one
文摘[Objective]The construction of weirs changes the hydraulic characteristics of rivers and affects the structure of phytoplankton communities and the health of aquatic ecosystems in the river.This study aims to explore the nonlinear response relationship between phytoplankton community structure and its driving factors in spring and autumn in Furong Creek under the construction of cascade weirs.[Methods]The structure of phytoplankton communities and related environmental factors were investigated in Furong Creek from 2023 to 2024.This study focused on the analysis of the changes of nutrient concentrations and biomass of phytoplankton in autumn and spring within the same dry season in Furong Creek.Redundancy analysis was used to identify the key factors influencing the structure of phytoplankton communities.The MIKE 11 model was employed to simulate the hydrodynamic changes in the river.Combined with total nitrogen and permanganate index,a GAM model of phytoplankton diversity index and hydrodynamic factors was developed,and the change of phytoplankton diversity after the optimized layout of the cascade weirs was fitted.[Results]The result showed that the annual average value of Shannon-Wiener diversity index of phytoplankton in Furong Creek was 2.79,which was in a state of mild pollution.A total of 239 species from 95 genera in 8 phyla were identified.Among the phytoplankton,Chlorophyta was the dominant group throughout the year in Furong Creek,followed by Bacillariophyta and Cyanophyta.The cell abundance of phytoplankton ranged from 3.11 to 20.64 mg/L and from 0.23 to 6.31 mg/L in spring and autumn,which indicated a clear seasonal succession of phytoplankton community structure.Compared with autumn,the relative abundance of Cyanophyta significantly decreased in spring across the whole river section,while Chrysophyta and Dinophyta showed significant increase at some monitoring sites,leading to water bloom phenomenon and a noticeable decline in the diversity of phytoplankton.The dominant species in the water bodies throughout the year were Cyclotella catenata,Chlorella vulgaris,Scenedesmus bijuga,Scenedesmus quadricauda,Chroomonas acuta,Cryptomonas ovata,and Cryptomonas erosa.Redundancy analysis(RDA)showed that hydrodynamic factors(v,h)and water environmental factors(TN,COD_(Mn))were the main influencing factors of phytoplankton community structure.[Conclusion]The result show that the nutrient concentration,phytoplankton biomass,and density in Furong Creek in spring are significantly higher than in autumn.The GAM model,constructed by combining hydrodynamic and environmental factors,can effectively reflect the nonlinear relationship between phytoplankton diversity index and its driving factors.In spring,with an increase in nutrient concentration,the habitat conditions of low flow speed and high water depths formed by overflow weirs will lead to a decrease in the Shannon-Wiener index of phytoplankton and an intensified risk of eutrophication.However,a reasonable layout scheme of cascade weirs will improve the diversity of phytoplankton and reduce the risk of eutrophication in the river.The findings of this study can help deepen the understanding of the ecological and environmental effects of cascade weir construction in the river.
基金Project(2021YFC2902102)supported by the National Key Research and Development Program of ChinaProject(52374142)supported by the National Natural Science Foundation of ChinaProject(JSTU-2022-066)supported by the Young Talent Support Project of Jiangsu Association for Science and Technology,China。
文摘Roof disaster has always been an important factor restricting coal mine safety production.Acidic effect can reform the rock mass structure to weaken the macroscopic strength characteristics,which is an effective way to control the hard limestone roof.In this study,the effects of various factors on the reaction characteristics and mechanical properties of limestone were analyzed.The results show that the acid with stronger hydrogen production capacity after ionization(pK_(a)<0)has more prominent damage to the mineral grains of limestone.When pKa increases from−8.00 to 15.70,uniaxial compressive strength and elastic modulus of limestone increase by 117.22%and 75.98%.The influence of acid concentration is manifested in the dissolution behavior of mineral crystals,the crystal defects caused by large-scale acid action will lead to the deterioration of limestone strength,and the strength after 15%concentration reformation can be reduced by 59.42%.The effect of acidification time on limestone has stages and is the most obvious in the initial metathesis reaction stage(within 60 min).The key to the strength damage of acidified limestone is the participation of hydrogen ions in the reaction system.Based on the analytic hierarchy process method,the influence weights of acid type,acid concentration and acidification time on strength are 24.30%,59.54% and 16.16%,respectively.The research results provide theoretical support for the acidification control of hard limestone roofs in coal mines.
基金Supported by the National Natural Science Foundation Project (71173035)the National Soft Science Research Plan (2010GXQ5D330)the Plan for Key Teachers of Heilongjiang Province (GC10D206)
文摘To make grain price stable is an important goal for the Chinese government. The paper compared the grain supply elasticity and demand elasticity to determine the grain price stability in China; used ＂k value＂ method to analyze the grain price fluctuation from 1985 to 2010; divided the grain price volatility into three stages; and analyzed the factors in each phase. On the base, it put forward some countermeasures to guarantee the stability of the grain price.
文摘[Objective]The channel straightening project of the Pinglu Canal has fragmented the river course,compromising the integrity of original river course and causing ecosystem patchiness.Understanding the current status of fish resources and the characteristics of their diversity is crucial for the ecological management of the Pinglu Canal.[Methods]During the spring and autumn in 2021 and 2022,a survey of fish resources and species diversity in the Pinglu Canal was conducted using multi-mesh gill nets.A total of 125 fish species were collected,belonging to 10 orders,34 families,and 89 genera.[Results]The result showed that the Pinglu Canal contained three nationally protected Class II species,two endemic species of the Qinjiang River,three anadromous/migratory species,and eight invasive species,accounting for 2.4%,1.6%,2.4%,and 6.4%of the total species,respectively.The fish community primarily consisted of mid-and bottom-dwelling,adhesive-egg-laying,and omnivorous species.The Shannon-Wiener,Simpson,Margalef,and Pielou indices of the fish community in the Pinglu Canal ranged from 2.347 to 2.757,0.081 to 0.151,3.493 to 4.382,and 0.812 to 0.892,respectively.These indices showed relatively uniform distribution across different river reaches.[Conclusion]The result indicate that the fish community structure in the Pinglu Canal is relatively uniform.The reach from the Yujiang River to the Shaping River shows higher stability,while other river reaches experience moderate or severe disturbances.This study provides supplementary baseline data on the fish community structure in the Pinglu Canal and explores the potential impact of inter-basin connectivity on fish resources,aiming to provide a scientific basis for habitat restoration assessments after the channel straightening project.
基金the financial support of the Shanxi Fire & Explosion-Proofing Safety Engineering and Technology Research Center, North University of China。
文摘Due to the presence of nitro groups, the dust generated during the production and utilization of energetic materials may potentially lead to dust explosion even under low-oxygen or anaerobic conditions.Considering the high energy density of energetic materials, dust explosion can cause serious production safety accidents. Therefore, it is necessary to understand the dust explosion characteristics of energetic materials and the mechanism of dust explosion. According to the literature review, among various influencing factors, the physical and chemical properties of dust are the decisive factors affecting the explosion characteristics of dust. In addition to experimental studies, numerical simulation is another important tool. However, it is subjected to certain limitations. Moreover, it is essential but challenging to fully understand the underlying mechanism. In addition, given the safety hazards posed by dust explosion, explosion suppression has attracted extensive attention for research. Depending on the medium used, there are different forms of suppression, including powder explosion suppression, water spray explosion suppression, inert gas explosion suppression, porous material explosion suppression, and vacuum chamber explosion suppression. As for the selection of explosion suppression agent, consideration must be given to the characteristics of the material. Furthermore, the above research has laid a foundation for discussing the future progress in studying dust explosion of energetic materials, with nano dust and the constraints of existing technology as the focal point.
基金supported by the Foundation Strengthening Program Technology Field Foundation(2020-JCJQ-JJ-132)。
文摘The interception probability of a single missile is the basis for combat plan design and weapon performance evaluation,while its influencing factors are complex and mutually coupled.Existing calculation methods have very limited analysis of the influence mechanism of influencing factors,and none of them has analyzed the influence of the guidance law.This paper considers the influencing factors of both the interceptor and the target more comprehensively.Interceptor parameters include speed,guidance law,guidance error,fuze error,and fragment killing ability,while target performance includes speed,maneuverability,and vulnerability.In this paper,an interception model is established,Monte Carlo simulation is carried out,and the influence mechanism of each factor is analyzed based on the model and simulation results.Finally,this paper proposes a classification-regression neural network to quickly estimate the interception probability based on the value of influencing factors.The proposed method reduces the interference of invalid interception data to valid data,so its prediction accuracy is significantly better than that of pure regression neural networks.
基金Project(51775561)supported by the National Natural Science Foundation of ChinaProject(20130162110004)supported by the National Doctoral Foundation of China
文摘The mathematical and simulation models of working head in the deep-sea working environment were built to analyze the effects of cutter-suction flow,cutter-head rotating speed,cutting depth and suction port position on the cutter-suction capacity.The efficiency of the cutter-suction is analyzed based on the analysis of the variation law of the solid-phase volume fraction of the flow field,the variation law of the velocity distribution in the flow field and the distribution law of the solid-phase concentration.The results show that the increase of cutter-suction flow can significantly improve the cutter-suction efficiency when it is less than1000m3/h.However,when it is more than1000m3/h,it is helpless.When the cutter-head rotate speed is within the range of10–25r/min,the cutter-suction efficiency stabilizes at about95%.While the speed is greater than25r/min,the cutter-suction efficiency decreases sharply with the increase of cutter-head rotate speed.With the increase of cutting depth,the cutter-suction efficiency first increases and then remains stable and finally decreases.The cutter-suction efficiency remains at about94%when the suction port position deviation ranges from0°to30°,but it has a sharply reduction when the deviation angle is more than30°.
基金Supported by the Achievement of Program for New Century Excellent Talents in Heilongjiang Province (1153-NCET-004)Project of Postdoctoral Scientific Research Launch Foundation in Heilongjiang Province
文摘Heilongjiang Province is an important marketable grain depot in China. Since the reform and opening up, Heilongjiang Province production capacity of foodstuff is increasingly growing into a new level. This paper started with the actuality of Heilongjiang Province integrated production capacity of foodstuff, and analyzed its major factors empirically through the mathematical model, then proposed some measures to enhance Heilongjiang Province production capacity of foodstuff which ensured China foodstuff security
基金Project(51606224) supported by the National Natural Science Foundation of China
文摘The recently proposed interface propagation-based method has shown its advantages in obtaining the thermal conductivity of phase change materials during solid-liquid transition over conventional techniques. However, in previous investigation, the analysis on the measurement error was qualitative and only focused on the total effects on the measurement without decoupling the influencing factors. This paper discusses the effects of influencing factors on the measurement results for the interface propagation-based method. Numerical simulations were performed to explore the influencing factors, namely model simplification, subcooling and natural convection, along with their impact on the measurement process and corresponding measurement results. The numerical solutions were provided in terms of moving curves of the solid-liquid interface and the predicted values of thermal conductivity. Results indicated that the impact of simplified model was strongly dependent on Stefan number of the melting process. The degree of subcooling would lead to underestimated values for thermal conductivity prediction. The natural convection would intensify the heat transfer rate in the liquid region, thereby overestimating the obtained results of thermal conductivity. Correlations and experimental guidelines are provided. The relative errors are limited in ±1.5%,±3%and ±2% corresponding to the impact of simplified model, subcooling and natural convection, respectively.
基金TheNationalNaturalScienceFoundationofChina (No .5 0 0 74 0 34)
文摘The granular dynamic shear strength is the same as that of the static one in nature, as found from numerous experiments and investigations. The shear strength is equal to the sum of the internal frictional force and the cohesive force. The influences of type, shape, size distribution, pore ratio, moisture content and variation of vibration velocity on the dynamic shear strength of granules were studied. Based on numerous vibration shear experiments, the authors investigate the mechanism of dynamic shear strength in granules in terms of the fundamental principle and the relevant theory of modern tribology.
文摘As a new mode to offer finance support in rural areas, the establishment of rural banks provide not only service and support for the agricultural development and rural economy, but also solutions to the issue of long-standing fund shortage and poverty in China. However, there are still a lot of problems that restrict the development of rural banks, such as unreasonable property right, unsound system of management as well as rural social credit, lacking of high-quality employees, innovation, policy support, supervision system, social awareness. Therefore, the analytic hierarchy process was employed in the current study with the aim of figuring out the essential factors which restricted the development of rural banks from two aspects of internal factors and external factors, furthermore, relevant suggestions were put forward.
基金Project(51021004)supported by Innovative Research Groups of the National Natural Science Foundation of ChinaProject(NCET-11-0370)supported by Program for New Century Excellent Talents in Universities of China+1 种基金Project(40776055)supported by the National Natural Science Foundation of ChinaProject(1002)supported by State Key Laboratory of Ocean Engineering Foundation,China
文摘In order to avoid the curing effects of paraffin on the transport process and reduce the transport difficulty,usually high temperature and high pressure are used in the transportation of oil and gas.The differences of temperature and pressure cause additional stress along the pipeline,due to the constraint of the foundation soil,the additional stress can not release freely,when the additional stress is large enough to motivate the submarine pipelines buckle.In this work,the energy method is introduced to deduce the analytical solution which is suitable for the global buckling modes of idealized subsea pipeline and analyze the relationship between the critical buckling temperature,buckling length and amplitude under different high-order global lateral buckling modes.To obtain a consistent formulation of the problem,the principles of virtual displacements and the variation calculus for variable matching points are applied.The finite element method based on elasto-plastic theory is used to simulate the lateral global buckling of the pipelines under high temperature and pressure.The factors influencing the lateral buckling of pipelines are further studied.Based upon some actual engineering projects,the finite element results are compared with the analytical ones,and then the influence of thermal stress,the section rigidity of pipeline,the soil properties and the trigging force to the high order lateral buckling are discussed.The method of applying the small trigging force on pipeline is reliable in global buckling numerical analysis.In practice,increasing the section rigidity of a pipeline is an effective measure to improve the ability to resist the global buckling.
基金Projects(51004082,51222406)supported by the National Natural Science Foundation of ChinaProject(NCET-12-1061)supported by the New Century Excellent Talents in University of ChinaProjects(12TD007,2011JQ0020)supported by Scientific Research Innovation Team Project of Sichuan and the Sichuan Youth Sci-tech Fund,China
文摘In the view of the problems existing in horizontal well,such as sand depositing and cleaning difficulty of borehole,a technology with rotating jet suitable to resolution of the problems was presented.Based on liquid solid two-phase flow theory,the analyses on the sand movement law and the swirling field influential factors were conducted.Results show that:1) With the increasing of displacement in horizontal section annulus,swirling field strength increases,and when the displacement is constant,the closer from the nozzle,the stronger the swirling field strength is;2) Head rotating speed and liquid viscosity have little influence on the swirling field strength,but the sand-carrying rate of fluid can increase by increasing liquid viscosity in a certain range;3) Rotating the string and reducing its eccentricity in annulus are conducive for sand migration in the annulus;4) The sand can be suspended and accelerated again and the swirling field strength is enhanced by the helix agitator.Hence,the research results provide the theoretical basis for the design and application of rotating jet tool.
基金Project(50978043) supported by the National Natural Science Foundation of China
文摘The study was motivated by the fact that explosion inside the subway structure may not only cause direct life loss,but also damage the subway structure and lead to further loss of lives and properties.The propagation law of explosion wave in the subway station was analyzed and a simplified model of overpressure in the subway station was also proposed.Whereafter,the improved dynamic cam-clay model of soil and the concrete damaged plasticity constitutive model were used for the dynamic analysis of the subway station.Meanwhile,the influences of soil stiffness and burial depth on the dynamic response of the subway station were looked into.The results show that the multi-peak overpressure in the subway station does not appear,and large stresses concentrate on the central column and the floor slab of the subway station,so some special reinforcement measures should be taken in these parts.The effect of soil stiffness and burial depth on the stress of the central column is little;however,the effect on the stress of the station side wall is relatively obvious.
基金A project funded by National Natural Science Foundation of China(41572093)Central Young College Teachers Fund Project (3142020002)Supported by the Fundamental Research Funds for the Central Universities(3142021004)。
文摘The Cretaceous is a typical period for studying the greenhouse climate and the earth system interactions, and the world’s most extensive terrestrial strata are mainly in East Asia, especially in China. Continental sediments can effectively reflect the paleo-climate change, but the previous studies of the Late Cretaceous paleo-climate, based on the combined characteristics of continental climate-sensitive sediments, were barely found in China. To obtain the Late Cretaceous paleo-climate characteristics of China, the distribution characteristics of different continental climate-sensitive sediment types in the early, middle and Late Cretaceous in China were studied in detail. According to the distribution and combination characteristics and types of continental climate-sensitive sediments, seven climate types can be divided: 1) warm-humid and warm-dry climate;2) hot and dry climate;3) hot-dry and arid climate;4) hot-dry and semiarid climate;5) hot-dry and hot-wet climate;6) hot-dry and warm-humid climate;7) hot-dry and warm-dry climate. The results show that in the early Late Cretaceous, the hot and dry climate was the most widespread, followed by warm-humid and warm-dry climate, but the climate was drier than the paleo-climate of the previous study of Early Cretaceous. Hot and dry climate zone became wider in the Coniacian and Maastrichtian;furthermore, it covered Xinjiang to the east of China from east to west after the Santonian Period. The hot-dry and semiarid climate zone was nearly latitudinally distributed from the northwest to the southeast and it shows a further increase in aridification. Global geological events, paleogeographic features and regional tectonic evolution had significant impacts on the paleoclimate of China in the Late Cretaceous, such as global eruptive events of volcanoes led to the temperature increase in China in the early Late Cretaceous;coastal mountain ranges in southeastern China led to the drying of the Late Cretaceous climate in southern China;Xuefeng Mountains, Wuling Mountains, Nanling Mountains and Tai-hang Mountains were the dividing line between the hot and dry climate zone and hot-dry and arid climate zone in the early Late Cretaceous, and Altun Mountains were the dividing line between the southeastern section of the hot and dry climate zone in western China in the middle Late Cretaceous.
文摘Chinese cultural identity has great significance in maintaining the unity of Chinese nation and promo-ting the development of Chinese culture.This paper explains the definition and development of Chinese cultural iden-tity.Research targets include Chinese cultural identity of collge students and Chinese cultural identity of Chinese eth-nic minorities.This paper also carries out a comparative research from an international perspective.Enhancing Chinese cultural identity not only has an important efect on the prosperity and development of Chinese culture,but also has far-reaching impact on the Chinese national identity.
基金Project(2019QZKK0905)supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)Program,ChinaProject(41901074)supported by the National Natural Science Foundation of China+2 种基金Project(2020A1515010745)supported by the Natural Science Foundation of Guangdong Province,ChinaProject(SKLFSE201810)supported by the Open Fund of the State Key Laboratory of Frozen Soil Engineering,ChinaProject(2019MS119)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Embankment stability is the primary problem for the expressway construction in permafrost regions.The proposed Qinghai-Tibet Expressway(QTE)is planned to construct along the Qinghai-Tibet Project Corridor.Confronted with harsh environmental condition and intense heat exchange between earth and atmosphere,it is necessary to predict and evaluate the stability of the proposed QTE.In this study,the factors affecting the embankment stability are analyzed firstly.And then,a scheme for the stability evaluation of the embankment is established.Finally,the evaluation scheme is used for the pre-evaluation of the stability for the proposed QTE with different geothermal regulation measures(GRMs).The results indicate that the influencing factors include climatic environment,permafrost property,engineering condition and geological condition,and among them,engineering condition and permafrost property are the main influence factors for embankment stability.The stability of the proposed QTE varies greatly in the different geomorphological regions.The application effect and contribution to embankment stability of the existing GRMs are different,and using GRMs cannot completely overcome the influence of various factors on expressway stability.In the construction process,different GRMs should be adopted depending on the geomorphological environment where the embankment is located to ensure the embankment stability.
基金Supported by the National Natural Science Foundation(71173035)Scientific and Technological Project of Heilongjiang Province(GZ11D101)+1 种基金Dr.Start Fund of Northeast Agricultural University(2012RCB78)Construction of Milk Base in China(Cooperation Project with Mengniu Companies)
文摘This paper elaborated dairy consumption status in Heilongjiang Province from seven aspects： dairy total consumption, comparison of dairy consumption between urban and rural, dairy consumption under different income levels, consumption category structure, consumption brand structure, consumption channels and consumer information source. On this basis, factors affecting dairy consumption and trends of dairy consumption were further analyzed. The result showed that dairy consumption potential of Heilongjiang Province should be excavated. On one hand, rural consumer market should be further developed; on the other hand, dairy consumption market should be further broken down to meet different needs of different groups of people.
