The implementation of long-term shelterbelt programs in the middle reaches of the Yellow River(MRYR),China not only has improved the overall ecological environment,but also has led to the changes of land use pattern,c...The implementation of long-term shelterbelt programs in the middle reaches of the Yellow River(MRYR),China not only has improved the overall ecological environment,but also has led to the changes of land use pattern,causing carbon storage exchanges.However,the relationship between carbon storage and land use change in the MRYR is not concerned,which results in the uncertainty in the simulation of carbon storage in this area.Land use changes directly affect the carbon storage capacity of ecosystems,and as an indicator reflecting the overall state of land use,land use degree has an important relationship with carbon storage.In this study,land use data and the integrated valuation of ecosystem services and trade-offs(InVEST)model were used to assess the trends in land use degree and carbon storage in the MRYR during 1980-2020.The potential impact index and the standard deviation ellipse(SDE)algorithm were applied to quantify and analyze the characteristics of the impact of land use changes on carbon storage.Subsequently,land use transitions that led to carbon storage variations and their spatial variations were determined.The results showed that:(1)the most significant periods of carbon storage changes and land use transitions were observed during 1990-1995 and 1995-2020,with the most changed areas locating in the east of Fenhe River and in northwestern Henan Province;(2)the positive impact of land use degree on carbon storage may be related to the environmental protection measures implemented along the Yellow River,while the negative impact may be associated with the expansion of construction land in plain areas;and(3)the conversion of other land use types to grassland was the primary factor affecting carbon storage changes during 1980-2020.In future land use planning,attention should be given to the direction of grassland conversion,and focus on reasonably limiting the development of construction land.To enhance carbon storage,it will be crucial to increase the area of high-carbon-density land types,such as forest land and grassland under the condition that the area of permanent farmland does not decrease.展开更多
In this study,to better decide the effect of coal seam dip angle upon the dynamic change of the crossfusion in gas transport and storage areas during the progress of working face in the high gas thick coal seam,a two-...In this study,to better decide the effect of coal seam dip angle upon the dynamic change of the crossfusion in gas transport and storage areas during the progress of working face in the high gas thick coal seam,a two-dimensional physical simulation experiment regarded as the theoretical research was conducted to properly explore the variation law of overburden fracture.The results demonstrated that the boundary of the gas transport zone was located in the region of fracture separation.The boundary of the gas storage area was located in the abrupt penetration zone.Also,according to the information theory,the state of the gas transport and storage areas was determined by the changing trend of the fracture rate and fracture entropy.The mathematical representation model of the dip effect in gas transport and storage areas was established.The criteria upon which the regional location of the gas transport area and gas storage area can be based were put forward.The cross-fusion evolution process of the dip effect in gas transport and storage areas was revealed as well.The research results could provide guidance for realising directional and accurate gas extraction.展开更多
Triaxial compression tests were conducted on the alfalfa root-loess complex at different growthperiods obtained through artificial planting.The research focused on analyzing the time variation law of the shear strengt...Triaxial compression tests were conducted on the alfalfa root-loess complex at different growthperiods obtained through artificial planting.The research focused on analyzing the time variation law of the shear strength index and deformation index of the alfalfa root-loess complex under dry-wet cycles.Additionally,the time effect of the shear strength index of the alfalfa root-loess complex under dry-wet cycles was analyzed and its prediction model was proposed.The results show that the PG-DWC(dry-wet cycle caused by plant water management during plant growth period)causes the peak strength of plain soil to change in a"V"shape with the increase of growth period,and the peak strength of alfalfa root-loess complex is higher than that of plain soil at the same growth period.The deterioration of the peak strength of alfalfa root-loess complex in the same growth period is aggravated with the increase of drying and wetting cycles.Compared with the 0 days growth period,the effective cohesion of alfalfa root-loess complex under different dry-wet cycles maximum increase rate is at the 180 days,which are 33.88%,46.05%,30.12%and 216.02%,respectively.When the number of dry-wet cycles is constant,the effective cohesion of the alfalfa root-loess complex overall increases with the growth period.However,it gradually decreases comparedwith the previous growth period,and the minimum increase rate are all at the 180 days.For the same growth period,the effective cohesion of the alfalfa root-loess complex decreases with the increase of the number of dry-wet cycles.This indicates that EC-DWC(the dry-wet cycles caused by extreme natural conditions such as continuous rain)have a detrimental effect on the time effect of the shear strength of the alfalfa root-loess complex.Finally,based on the formula of total deterioration,a prediction model for the shear strength of the alfalfa root-loess complex under dry-wet cycles was proposed,which exhibits high prediction accuracy.The research results provide useful guidance for the understanding of mechanical behavior and structural damage evolution of root-soil composite.展开更多
The vegetation growth status largely represents the ecosystem function and environmental quality.Hyperspectral remote sensing data can effectively eliminate the effects of surface spectral reflectance and atmospheric ...The vegetation growth status largely represents the ecosystem function and environmental quality.Hyperspectral remote sensing data can effectively eliminate the effects of surface spectral reflectance and atmospheric scattering and directly reflect the vegetation parameter information.In this study,the abandoned mining area in the Helan Mountains,China was taken as the study area.Based on hyperspectral remote sensing images of Zhuhai No.1 hyperspectral satellite,we used the pixel dichotomy model,which was constructed using the normalized difference vegetation index(NDVI),to estimate the vegetation coverage of the study area,and evaluated the vegetation growth status by five vegetation indices(NDVI,ratio vegetation index(RVI),photochemical vegetation index(PVI),red-green ratio index(RGI),and anthocyanin reflectance index 1(ARI1)).According to the results,the reclaimed vegetation growth status in the study area can be divided into four levels(unhealthy,low healthy,healthy,and very healthy).The overall vegetation growth status in the study area was generally at low healthy level,indicating that the vegetation growth status in the study area was not good due to short-time period restoration and harsh damaged environment such as high and steep rock slopes.Furthermore,the unhealthy areas were mainly located in Dawukougou where abandoned mines were concentrated,indicating that the original mining activities have had a large effect on vegetation ecology.After ecological restoration of abandoned mines,the vegetation coverage in the study area has increased to a certain extent,but the amplitude was not large.The situation of vegetation coverage in the northern part of the study area was worse than that in the southern part,due to abandoned mines mainly concentrating in the northern part of the Helan Mountains.The combination of hyperspectral remote sensing data and vegetation indices can comprehensively extract the characteristics of vegetation,accurately analyze the plant growth status,and provide technical support for vegetation health evaluation.展开更多
Gas emissions of workfaces in steeply inclined and extremely thick coal seams differ from those under normal geological conditions, which usually feature a high gas concentration and a large emission quantity. This st...Gas emissions of workfaces in steeply inclined and extremely thick coal seams differ from those under normal geological conditions, which usually feature a high gas concentration and a large emission quantity. This study took the Wudong coal mine in Xinjiang province of China as a typical case. The gas occurrence of the coal seam and the pressure-relief range of the surrounding rock(coal) were studied by experiments and numerical simulations. Then, a new method to calculate the gas emission quantity for this special geological condition was provided. Based on the calculated quantity, a further gas drainage plan, as well as the evaluation of it with field drainage data, was finally given. The results are important for engineers to reasonably plan the gas drainage boreholes of steeply inclined and extremely thick coal seams.展开更多
Changes in water resource storage are inevitable due to climate change and human activities,thus understanding alterations in water storage within a specific region is imperative for the planning and management of wat...Changes in water resource storage are inevitable due to climate change and human activities,thus understanding alterations in water storage within a specific region is imperative for the planning and management of water resources.Data from the Gravity Recovery and Climate Experiment(GRACE)satellite mission are extensively employed to analyze large-scale total terrestrial water storage anomalies(TWSA).In this study,we derived a more reliable TWSA using different types of GRACE gravity models,which served as the basis for evaluating spatial and temporal variations in total terrestrial water storage and its hydrological components(soil moisture and groundwater)across the Loess Plateau.Additionally,we analyzed the impact of natural and anthropogenic influences on water storage in the Loess Plateau,categorizing them into primary and secondary influences,utilizing data on climate and human activities.The findings revealed a declining trend in the overall TWSA of the Loess Plateau,with a rate of decrease at-0.65±0.05 cm/yr from 2003 to 2020(P<0.01).As the direct factors affecting TWSA,soil moisture dominated the change of TWSA before 2009,and groundwater dominated the change of TWSA after 2009.Spatially,there was variability in the changes of TWSA in the Loess Plateau.More in-depth studies showed that soil moisture changes in the study area were primarily driven by evapotranspiration and temperature,with precipitation and vegetation cover status playing a secondary role.Human activities had a secondary effect on soil moisture in some sub-regions.Population change and agricultural development were major factors in altering groundwater storage in the study area.Other than that,groundwater was influenced by natural factors to a limited extent.These findings provided valuable insights for local governments to implement proactive water management policies.展开更多
The reliability theory has been an important element of the classical geodetic adjustment theory and methods in the linear Gauss-Markov model. Although errors-in-variables(EIV) models have been intensively investigate...The reliability theory has been an important element of the classical geodetic adjustment theory and methods in the linear Gauss-Markov model. Although errors-in-variables(EIV) models have been intensively investigated, little has been done about reliability theory for EIV models. This paper first investigates the effect of a random coefficient matrix A on the conventional geodetic reliability measures as if the coefficient matrix were deterministic. The effects of such geodetic internal and external reliability measures due to the randomness of the coefficient matrix are worked out, which are shown to depend not only on the noise level of the random elements of A but also on the values of parameters. An alternative, linear approximate reliability theory is accordingly developed for use in EIV models. Both the EIV-affected reliability measures and the corresponding linear approximate measures fully account for the random errors of both the coefficient matrix and the observations, though formulated in a slightly different way. Numerical experiments have been carried to demonstrate the effects of errors-in-variables on reliability measures and compared with the conventional Baarda's reliability measures. The simulations have confirmed our theoretical results that the EIV-reliability measures depend on both the noise level of A and the parameter values. The larger the noise level of A, the larger the EIV-affected internal and external reliability measures;the larger the parameters,the larger the EIV-affected internal and external reliability measures.展开更多
The phase stability,elastic anisotropy,and minimum thermal conductivity of MnB_(2) in different crystal structures have been investigated by first-principles calculations based on density functional theory.The results...The phase stability,elastic anisotropy,and minimum thermal conductivity of MnB_(2) in different crystal structures have been investigated by first-principles calculations based on density functional theory.The results found that P6_(3)/mmc(hP6-MnB_(2)),P6/mmm(hP3-MnB_(2)),Pmmn(oP6-MnB_(2)),R■m(hR3-MnB_(2)),Pnma(oP12-MnB_(2)),and Immm(oI18-MnB_(2))all exhibit mechanical and dynamic stability under environmental conditions,and the sequence of phase stability was hP6>hR3>oP6>0I18>oP 12>hP3.In addition,Vickers hardness calculations indicated that hP6,hR3,oP6,and oI18of MnB_(2)have potential as hard materials,while hP3 and oP12 are not suitable as hard materials.Moreover,the elastic anisotropy of different MnB_(2)phases were also comprehensively investigated.It is found that the anisotropic order of bulk modulus is oP12>hP3>hP6>hR3>oI18>oP6,while that of Young's modulus is oP12>hR3>hP6>oP6>hP3>oI18.Furthermore,the minimum thermal conductivity of different MnB_(2)phases was evaluated by means of Clarke's and Cahill's models.The results suggested that these MnB_(2) diborides are all not suitable as thermal barrier coating materials.展开更多
NiO,an anodic electrochromic material,has applications in energy-saving windows,intelligent displays,and military camouflage.However,its electrochromic mechanism and reasons for its performance degradation in alkaline...NiO,an anodic electrochromic material,has applications in energy-saving windows,intelligent displays,and military camouflage.However,its electrochromic mechanism and reasons for its performance degradation in alkaline aqueous electrolytes are complex and poorly understood,making it challenging to improve NiO thin films.We studied the phases and electrochemical characteristics of NiO films in different states(initial,colored,bleached and after 8000 cycles)and identified three main reasons for performance degradation.First,Ni(OH)_(2)is generated during electrochromic cycling and deposited on the NiO film surface,gradually yielding a NiO@Ni(OH)_(2)core-shell structure,isolating the internal NiO film from the electrolyte,and preventing ion transfer.Second,the core-shell structure causes the mode of electrical conduction to change from first-to second-order conduction,reducing the efficiency of ion transfer to the surface Ni(OH)_(2)layer.Third,Ni(OH)_(2)and NiOOH,which have similar crystal structures but different b-axis lattice parameters,are formed during electrochromic cycling,and large volume changes in the unit cell reduce the structural stability of the thin film.Finally,we clarified the mechanism of electrochromic performance degradation of NiO films in alkaline aqueous electrolytes and provide a route to activation of NiO films,which will promote the development of electrochromic technology.展开更多
In order to promote the development and utilization of desert sand,this study is based on researching the most suitable ratio of bio-cement,analyzing the shear strength and permeability of improved desert sand by comb...In order to promote the development and utilization of desert sand,this study is based on researching the most suitable ratio of bio-cement,analyzing the shear strength and permeability of improved desert sand by combining bio-cement and fly ash,and clarifying the applicability of tap water in bio-cement.The relationship between the two and the microstructural properties was investigated using the results of the straight shear test and the permeability test.The results showed that the urease solution prepared with tap water had a more pronounced temperature resistance.The urea concentration and the corresponding pH environment had a direct effect on the urease activity.The calcium carbonate yield was positively correlated with the calcium concentration,and the urea concentration was higher in the ranges of 1.0-1.5 mol/L.As the enzyme-to-gel ratio decreased,the calcium carbonate precipitate produced per unit volume of urease solution gradually converged to a certain value.The shear strength(increased by 37.9%)and permeability(decreased by about 8.9-68.5%)of the modified desert sand peaked with the increase in fly ash content.The microscopic test results indicated that the fly ash could provide nucleation sites for the bio-cement,effectively improving the mechanical properties of the desert sand.The crystal types of calcium carbonate in the modified desert sand were calcite and aragonite,which were the most stable crystal types.This study provides innovative ideas for interdisciplinary research in the fields of bioengineering,ecology and civil engineering.展开更多
The Science of Land Management is a course integrating theory and practice closely.In order to improve the teaching effect of the course and practice the course,this paper discussed practice work related to main conte...The Science of Land Management is a course integrating theory and practice closely.In order to improve the teaching effect of the course and practice the course,this paper discussed practice work related to main contents of the Science of Land Management.On the basis of taking overall consideration of the status and functions of this course in the entire teaching system,this paper designed three practice teaching parts closely connected with the core contents.This is of realistic significance for improving the teaching quality of the Science of Land Management.展开更多
In this paper, 5 high-rise hotels in Xi'an were selected for research, their energy consumption data from 2015 to 2016 were collected and analyzed, their comprehensive energy consumption per unit area was compared...In this paper, 5 high-rise hotels in Xi'an were selected for research, their energy consumption data from 2015 to 2016 were collected and analyzed, their comprehensive energy consumption per unit area was compared by using the standard coal coefficient, and their energy use characteristics and influencing factors were obtained. The test analyzed various parameters of the indoor environment and evaluated the indoor environmental quality according to the specifications and standards. Starting from the perspective of energy use systems, this paper found energy consumption priorities and problems of these hotels, and proposed feasible energy conservation measures, in a view to providing a reference for energy conservation design of high-rise hotels in Xi'an.展开更多
The eastern Hexi Corridor Belt（HCB） is located in the transitional belt among the Alxa Block,the Qilian Orogenic Belt and the North China Block. Because of its unique tectonic location, the tectonic setting, provena...The eastern Hexi Corridor Belt（HCB） is located in the transitional belt among the Alxa Block,the Qilian Orogenic Belt and the North China Block. Because of its unique tectonic location, the tectonic setting, provenance, and even the age of the sedimentary strata in the eastern HCB during the Early Paleozoic remain controversial. This study analyzes the provenance of the poorly studied Xiangshan Group, discusses its age of development and tectonic setting in the eastern HCB using a combination of petrological, geochemical and LA-ICP-MS U-Pb zircon dating methods. Based on the youngest age peaks and the fossil evidence, we suggest that the Xiangshan Group is Middle Cambrian to Late Ordovician in age. The complexity of the geochemical characteristics and associated diagrams suggests that the early stage of the Xiangshan Group developed in a passive continental margin environment, late in the backarc basin of the eastern HCB. Based on the sandstone detrital composition, whole-rock geochemistry and detrital zircon ages, we conclude that the Xiangshan Group had an early provenance that was mainly from the Qilian Block and a late provenance from the Qilian Block and the western Alxa Block. The eastern HCB and its northern and southern blocks have similar palaeontology, lithology and basement age characteristics to the South China Block. This indicates that the eastern HCB might not have formed in the intra-continental aulacogen of the North China Block during the Early Paleozoic but has a close affinity to eastern Gondwana.展开更多
Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studi...Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L. （alfalfa） grassland biomass carbon and soil organic carbon density （SOCD） in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period （viz. 0-10 year）. Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0-10 year. During 0-30 year, the SOCD from 0-100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for l0 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.展开更多
The methods of nuclear magnetic resonance(NMR)spectroscopy,mercury injection porosimetry(MIP),and gas-water relative permeability(GWRP)were used to reveal the pore structure and permeability characteristics of high-ra...The methods of nuclear magnetic resonance(NMR)spectroscopy,mercury injection porosimetry(MIP),and gas-water relative permeability(GWRP)were used to reveal the pore structure and permeability characteristics of high-rank coal reservoirs in the Bide-Santang basin,western Guizhou,South China,to provide guidance for coalbed methane(CBM)exploration and exploitation and obtain direct insights for the development of CBM wells.The results indicate that the coal reservoirs in the study area are characterized by well-developed adsorption pores and poorly developed seepage pores.The bimodal NMR transverse relaxation time(T2)spectra and the mutation in the fractal characteristic of the MIP pore volume indicate poor connectivity between the adsorption pores and the seepage pores.As a result,the effective porosity is relatively low,with an average of 1.70%.The irreducible water saturation of the coal reservoir is relatively high,with an average of 66%,leading to a low gas relative permeability under irreducible water saturation.This is the main reason for the low recovery of high-rank CBM reservoirs,and effective enhanced CBM recovery technology urgently is needed.As a nondestructive and less time-consuming technique,the NMR is a promising method to quantitatively characterize the pores and fractures of coals.展开更多
In some studies on landslide susceptibility mapping(LSM),landslide boundary and spatial shape characteristics have been expressed in the form of points or circles in the landslide inventory instead of the accurate pol...In some studies on landslide susceptibility mapping(LSM),landslide boundary and spatial shape characteristics have been expressed in the form of points or circles in the landslide inventory instead of the accurate polygon form.Different expressions of landslide boundaries and spatial shapes may lead to substantial differences in the distribution of predicted landslide susceptibility indexes(LSIs);moreover,the presence of irregular landslide boundaries and spatial shapes introduces uncertainties into the LSM.To address this issue by accurately drawing polygonal boundaries based on LSM,the uncertainty patterns of LSM modelling under two different landslide boundaries and spatial shapes,such as landslide points and circles,are compared.Within the research area of Ruijin City in China,a total of 370 landslides with accurate boundary information are obtained,and 10 environmental factors,such as slope and lithology,are selected.Then,correlation analyses between the landslide boundary shapes and selected environmental factors are performed via the frequency ratio(FR)method.Next,a support vector machine(SVM)and random forest(RF)based on landslide points,circles and accurate landslide polygons are constructed as point-,circle-and polygon-based SVM and RF models,respectively,to address LSM.Finally,the prediction capabilities of the above models are compared by computing their statistical accuracy using receiver operating characteristic analysis,and the uncertainties of the predicted LSIs under the above models are discussed.The results show that using polygonal surfaces with a higher reliability and accuracy to express the landslide boundary and spatial shape can provide a markedly improved LSM accuracy,compared to those based on the points and circles.Moreover,a higher degree of uncertainty of LSM modelling is present in the expression of points because there are too few grid units acting as model input variables.Additionally,the expression of the landslide boundary as circles introduces errors in measurement and is not as accurate as the polygonal boundary in most LSM modelling cases.In addition,the results under different conditions show that the polygon-based models have a higher LSM accuracy,with lower mean values and larger standard deviations compared with the point-and circle-based models.Finally,the overall LSM accuracy of the RF is superior to that of the SVM,and similar patterns of landslide boundary and spatial shape affecting the LSM modelling are reflected in the SVM and RF models.展开更多
Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results,we built a thin plate mechanical model for layered and spalled coal bodies.We studied the mechanical...Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results,we built a thin plate mechanical model for layered and spalled coal bodies.We studied the mechanical mechanism of outbursts,due to instability,of thin plates of coal rocks under the action of in-plane load and normal load,by using the catastrophe theory.The total potential function is derived for the layered rock system,the cusp catastrophe model for the system is established,the bifurcation set that makes the system unstable is given,the process in which gradual change of action forces leads to catastrophic change of state is analyzed,and the effect of movement path of point(P,q) in the control space on the stability of rock plate is analyzed.The study results show that during the process of coal mining,the stability of the layered coal bodies depends not only on its physical properties and dimensions but also on the magnitudes and changing paths of the in-plane load and the normal load.When the gas in the coal bodies ahead of the mining face is pre-drained,the gas pressure can be reduced and the normal load q can be lowered.Consequently,disasters such as coal and gas outbursts can be effectively prevented.展开更多
In underground mines, high air temperatures in the summer months lead to an increase in inlet airflow temperatures. This leads to seasonal thermal pollution in the mines. This paper examines the dynamics and effects o...In underground mines, high air temperatures in the summer months lead to an increase in inlet airflow temperatures. This leads to seasonal thermal pollution in the mines. This paper examines the dynamics and effects of seasonal variation in surface air temperatures and surrounding rock temperatures in deep coal mines. It also examines temperature variations in the main ventilation circuit, working face, and surrounding rock. The study results revealed that airflow temperatures were significantly affected by seasonal air temperature variations. The greater the distance was between the inlet and the wellhead of the ventilation shaft, the less the effect was on temperature. Moreover, slight temperature variations (1.0-3.0 ℃) were observed between various points on the return route during the summer months. Airflow temperatures along the airflow inlet to the return route of the working face first decreased, but then increased. The temperature field of the surrounding rock increased gradually with increased distance between the mine roadway and inlet, with recorded rock temperatures as high as 40.53 ℃. The radius of the heat-adjusting layer was between 28 and 33 m.展开更多
By solving steady model of air flow diffusion and chemical reaction in loose coal, distribution of oxygen concentration and flow velocity magnitude were obtained. Compared the simulating results with critic value as w...By solving steady model of air flow diffusion and chemical reaction in loose coal, distribution of oxygen concentration and flow velocity magnitude were obtained. Compared the simulating results with critic value as well as duration of spontaneous combustion from large-scale spontaneous combustion experiment, 'three zones' of spontaneous combustion were partitioned and mining conditions to avoid spontaneous combustion were obtained. The above method was employed to partition 'three zones' in gob of fully mechanized top-coal caving long wall face and got fairly good result. Calculation of the above method is much smaller than simulating the whole process of coal spontaneous combustion, but the prediction precision can satisfy the demand of predicting and extinguishing spontaneous combustion in mining.展开更多
A novel V-doped CeO_(2)-supported alkali-activated-steel-slag-based catalyst(V-CeO_(2)/AC)for photocatalytic decomposition of water to hydrogen was prepared via co-impregnation method.The chemical composition,mineral ...A novel V-doped CeO_(2)-supported alkali-activated-steel-slag-based catalyst(V-CeO_(2)/AC)for photocatalytic decomposition of water to hydrogen was prepared via co-impregnation method.The chemical composition,mineral phase,morphology,and optical performances of the synthesized catalyst samples were characterized by XRF,XRD,SEM,UV-Vis DRS,and so on.XRD and SEM results show that calcium silicate hydrate(Ca1.5SiO3.5·xH2O)mineral phase is formed in the carrier sample,and the prepared catalyst specimens are made up of approximately 50 nm particles.After 6 hours of xenon lamp irradiation,the catalyst supported on V-doped 8wt%CeO_(2) exhibits the highest photocatalytic hydrogen production activity(8292μmol/g),which is attributed to the interaction between the V-doped CeO_(2) active components and FeO existed in catalyst carrier.A possible photocatalytic decomposition of water for hydrogen production mechanism over the V-8CeO_(2)/AC catalyst was proposed.展开更多
基金funded by the National Natural Science Foundation of China(52079103)the Outstanding Youth Science Fund of Xi'an University of Science and Technology(2024YQ2-02).
文摘The implementation of long-term shelterbelt programs in the middle reaches of the Yellow River(MRYR),China not only has improved the overall ecological environment,but also has led to the changes of land use pattern,causing carbon storage exchanges.However,the relationship between carbon storage and land use change in the MRYR is not concerned,which results in the uncertainty in the simulation of carbon storage in this area.Land use changes directly affect the carbon storage capacity of ecosystems,and as an indicator reflecting the overall state of land use,land use degree has an important relationship with carbon storage.In this study,land use data and the integrated valuation of ecosystem services and trade-offs(InVEST)model were used to assess the trends in land use degree and carbon storage in the MRYR during 1980-2020.The potential impact index and the standard deviation ellipse(SDE)algorithm were applied to quantify and analyze the characteristics of the impact of land use changes on carbon storage.Subsequently,land use transitions that led to carbon storage variations and their spatial variations were determined.The results showed that:(1)the most significant periods of carbon storage changes and land use transitions were observed during 1990-1995 and 1995-2020,with the most changed areas locating in the east of Fenhe River and in northwestern Henan Province;(2)the positive impact of land use degree on carbon storage may be related to the environmental protection measures implemented along the Yellow River,while the negative impact may be associated with the expansion of construction land in plain areas;and(3)the conversion of other land use types to grassland was the primary factor affecting carbon storage changes during 1980-2020.In future land use planning,attention should be given to the direction of grassland conversion,and focus on reasonably limiting the development of construction land.To enhance carbon storage,it will be crucial to increase the area of high-carbon-density land types,such as forest land and grassland under the condition that the area of permanent farmland does not decrease.
基金supported by the National Natural Science Foundation of China(No.5217-4205)Shaanxi Provincial Outstanding Youth Science Fund Project(No.2023-JC-JQ-40)+4 种基金National Key Research and Development Project(No.2023YFC3009004)Key Project of Shaanxi Provincial Department of Education(No.22JY040)Xinjiang Uygur Autonomous Region Key Research and Development Task Special Project(No.2022B01034-3)Key Laboratory of Green Coal Mining in Xinjiang,Ministry of Education(No.KLXGY-KA2404)Shaanxi Provincial Key Research and Development Task General Project(No.2024GX–YBXM-490)。
文摘In this study,to better decide the effect of coal seam dip angle upon the dynamic change of the crossfusion in gas transport and storage areas during the progress of working face in the high gas thick coal seam,a two-dimensional physical simulation experiment regarded as the theoretical research was conducted to properly explore the variation law of overburden fracture.The results demonstrated that the boundary of the gas transport zone was located in the region of fracture separation.The boundary of the gas storage area was located in the abrupt penetration zone.Also,according to the information theory,the state of the gas transport and storage areas was determined by the changing trend of the fracture rate and fracture entropy.The mathematical representation model of the dip effect in gas transport and storage areas was established.The criteria upon which the regional location of the gas transport area and gas storage area can be based were put forward.The cross-fusion evolution process of the dip effect in gas transport and storage areas was revealed as well.The research results could provide guidance for realising directional and accurate gas extraction.
基金received the Key Research and Development Project of Ningxia Hui Autonomous Region(2022BEG03052,2023BEG02072).
文摘Triaxial compression tests were conducted on the alfalfa root-loess complex at different growthperiods obtained through artificial planting.The research focused on analyzing the time variation law of the shear strength index and deformation index of the alfalfa root-loess complex under dry-wet cycles.Additionally,the time effect of the shear strength index of the alfalfa root-loess complex under dry-wet cycles was analyzed and its prediction model was proposed.The results show that the PG-DWC(dry-wet cycle caused by plant water management during plant growth period)causes the peak strength of plain soil to change in a"V"shape with the increase of growth period,and the peak strength of alfalfa root-loess complex is higher than that of plain soil at the same growth period.The deterioration of the peak strength of alfalfa root-loess complex in the same growth period is aggravated with the increase of drying and wetting cycles.Compared with the 0 days growth period,the effective cohesion of alfalfa root-loess complex under different dry-wet cycles maximum increase rate is at the 180 days,which are 33.88%,46.05%,30.12%and 216.02%,respectively.When the number of dry-wet cycles is constant,the effective cohesion of the alfalfa root-loess complex overall increases with the growth period.However,it gradually decreases comparedwith the previous growth period,and the minimum increase rate are all at the 180 days.For the same growth period,the effective cohesion of the alfalfa root-loess complex decreases with the increase of the number of dry-wet cycles.This indicates that EC-DWC(the dry-wet cycles caused by extreme natural conditions such as continuous rain)have a detrimental effect on the time effect of the shear strength of the alfalfa root-loess complex.Finally,based on the formula of total deterioration,a prediction model for the shear strength of the alfalfa root-loess complex under dry-wet cycles was proposed,which exhibits high prediction accuracy.The research results provide useful guidance for the understanding of mechanical behavior and structural damage evolution of root-soil composite.
基金This research was supported by the Ningxia Hui Autonomous Region Key Research and Development Plan(2022BEG03052).
文摘The vegetation growth status largely represents the ecosystem function and environmental quality.Hyperspectral remote sensing data can effectively eliminate the effects of surface spectral reflectance and atmospheric scattering and directly reflect the vegetation parameter information.In this study,the abandoned mining area in the Helan Mountains,China was taken as the study area.Based on hyperspectral remote sensing images of Zhuhai No.1 hyperspectral satellite,we used the pixel dichotomy model,which was constructed using the normalized difference vegetation index(NDVI),to estimate the vegetation coverage of the study area,and evaluated the vegetation growth status by five vegetation indices(NDVI,ratio vegetation index(RVI),photochemical vegetation index(PVI),red-green ratio index(RGI),and anthocyanin reflectance index 1(ARI1)).According to the results,the reclaimed vegetation growth status in the study area can be divided into four levels(unhealthy,low healthy,healthy,and very healthy).The overall vegetation growth status in the study area was generally at low healthy level,indicating that the vegetation growth status in the study area was not good due to short-time period restoration and harsh damaged environment such as high and steep rock slopes.Furthermore,the unhealthy areas were mainly located in Dawukougou where abandoned mines were concentrated,indicating that the original mining activities have had a large effect on vegetation ecology.After ecological restoration of abandoned mines,the vegetation coverage in the study area has increased to a certain extent,but the amplitude was not large.The situation of vegetation coverage in the northern part of the study area was worse than that in the southern part,due to abandoned mines mainly concentrating in the northern part of the Helan Mountains.The combination of hyperspectral remote sensing data and vegetation indices can comprehensively extract the characteristics of vegetation,accurately analyze the plant growth status,and provide technical support for vegetation health evaluation.
基金provided by the National Science and Technology Major Project (No. 2016ZX05043-005)
文摘Gas emissions of workfaces in steeply inclined and extremely thick coal seams differ from those under normal geological conditions, which usually feature a high gas concentration and a large emission quantity. This study took the Wudong coal mine in Xinjiang province of China as a typical case. The gas occurrence of the coal seam and the pressure-relief range of the surrounding rock(coal) were studied by experiments and numerical simulations. Then, a new method to calculate the gas emission quantity for this special geological condition was provided. Based on the calculated quantity, a further gas drainage plan, as well as the evaluation of it with field drainage data, was finally given. The results are important for engineers to reasonably plan the gas drainage boreholes of steeply inclined and extremely thick coal seams.
基金supported in part by the National Natural Science Foundation of China under Grant 42374037the State Key Laboratory of Geodesy and Earth’s Dynamics,Innovation Academy for Precision Measurement Science and Technology under Grant SKLGED2022-3-5in part by the Outstanding Youth Science Fund of Xi’an University of Science and Technology under Grant 2018YQ2-10。
文摘Changes in water resource storage are inevitable due to climate change and human activities,thus understanding alterations in water storage within a specific region is imperative for the planning and management of water resources.Data from the Gravity Recovery and Climate Experiment(GRACE)satellite mission are extensively employed to analyze large-scale total terrestrial water storage anomalies(TWSA).In this study,we derived a more reliable TWSA using different types of GRACE gravity models,which served as the basis for evaluating spatial and temporal variations in total terrestrial water storage and its hydrological components(soil moisture and groundwater)across the Loess Plateau.Additionally,we analyzed the impact of natural and anthropogenic influences on water storage in the Loess Plateau,categorizing them into primary and secondary influences,utilizing data on climate and human activities.The findings revealed a declining trend in the overall TWSA of the Loess Plateau,with a rate of decrease at-0.65±0.05 cm/yr from 2003 to 2020(P<0.01).As the direct factors affecting TWSA,soil moisture dominated the change of TWSA before 2009,and groundwater dominated the change of TWSA after 2009.Spatially,there was variability in the changes of TWSA in the Loess Plateau.More in-depth studies showed that soil moisture changes in the study area were primarily driven by evapotranspiration and temperature,with precipitation and vegetation cover status playing a secondary role.Human activities had a secondary effect on soil moisture in some sub-regions.Population change and agricultural development were major factors in altering groundwater storage in the study area.Other than that,groundwater was influenced by natural factors to a limited extent.These findings provided valuable insights for local governments to implement proactive water management policies.
基金supported by the National Natural Science Foundation of China, Project No. 42174045under National Key Research and Development Program of China, Project No.2020YFB0505805the National Natural Science Foundation of China, Project No. 41874012。
文摘The reliability theory has been an important element of the classical geodetic adjustment theory and methods in the linear Gauss-Markov model. Although errors-in-variables(EIV) models have been intensively investigated, little has been done about reliability theory for EIV models. This paper first investigates the effect of a random coefficient matrix A on the conventional geodetic reliability measures as if the coefficient matrix were deterministic. The effects of such geodetic internal and external reliability measures due to the randomness of the coefficient matrix are worked out, which are shown to depend not only on the noise level of the random elements of A but also on the values of parameters. An alternative, linear approximate reliability theory is accordingly developed for use in EIV models. Both the EIV-affected reliability measures and the corresponding linear approximate measures fully account for the random errors of both the coefficient matrix and the observations, though formulated in a slightly different way. Numerical experiments have been carried to demonstrate the effects of errors-in-variables on reliability measures and compared with the conventional Baarda's reliability measures. The simulations have confirmed our theoretical results that the EIV-reliability measures depend on both the noise level of A and the parameter values. The larger the noise level of A, the larger the EIV-affected internal and external reliability measures;the larger the parameters,the larger the EIV-affected internal and external reliability measures.
基金Project supported by the Natural Science Basic Research Program of Shaanxi Province,China(Grant No.2024JCYBQN-0044)the National Natural Science Foundation of China(Grant No.11904282)the Doctoral Scientific Research Foundation of Xi’an University of Science and Technology(Grant No.2018QDJ029)。
文摘The phase stability,elastic anisotropy,and minimum thermal conductivity of MnB_(2) in different crystal structures have been investigated by first-principles calculations based on density functional theory.The results found that P6_(3)/mmc(hP6-MnB_(2)),P6/mmm(hP3-MnB_(2)),Pmmn(oP6-MnB_(2)),R■m(hR3-MnB_(2)),Pnma(oP12-MnB_(2)),and Immm(oI18-MnB_(2))all exhibit mechanical and dynamic stability under environmental conditions,and the sequence of phase stability was hP6>hR3>oP6>0I18>oP 12>hP3.In addition,Vickers hardness calculations indicated that hP6,hR3,oP6,and oI18of MnB_(2)have potential as hard materials,while hP3 and oP12 are not suitable as hard materials.Moreover,the elastic anisotropy of different MnB_(2)phases were also comprehensively investigated.It is found that the anisotropic order of bulk modulus is oP12>hP3>hP6>hR3>oI18>oP6,while that of Young's modulus is oP12>hR3>hP6>oP6>hP3>oI18.Furthermore,the minimum thermal conductivity of different MnB_(2)phases was evaluated by means of Clarke's and Cahill's models.The results suggested that these MnB_(2) diborides are all not suitable as thermal barrier coating materials.
基金supported by the Special Support Program for High-level Talents of Shaanxi Province(No.2020-44)Innnovative Talent Project of China and The Youth Innovation Team of Shaanxi Universities
文摘NiO,an anodic electrochromic material,has applications in energy-saving windows,intelligent displays,and military camouflage.However,its electrochromic mechanism and reasons for its performance degradation in alkaline aqueous electrolytes are complex and poorly understood,making it challenging to improve NiO thin films.We studied the phases and electrochemical characteristics of NiO films in different states(initial,colored,bleached and after 8000 cycles)and identified three main reasons for performance degradation.First,Ni(OH)_(2)is generated during electrochromic cycling and deposited on the NiO film surface,gradually yielding a NiO@Ni(OH)_(2)core-shell structure,isolating the internal NiO film from the electrolyte,and preventing ion transfer.Second,the core-shell structure causes the mode of electrical conduction to change from first-to second-order conduction,reducing the efficiency of ion transfer to the surface Ni(OH)_(2)layer.Third,Ni(OH)_(2)and NiOOH,which have similar crystal structures but different b-axis lattice parameters,are formed during electrochromic cycling,and large volume changes in the unit cell reduce the structural stability of the thin film.Finally,we clarified the mechanism of electrochromic performance degradation of NiO films in alkaline aqueous electrolytes and provide a route to activation of NiO films,which will promote the development of electrochromic technology.
基金financially supported by National Natural Science Foundation of China(Grant no.42372323 and 42072319).
文摘In order to promote the development and utilization of desert sand,this study is based on researching the most suitable ratio of bio-cement,analyzing the shear strength and permeability of improved desert sand by combining bio-cement and fly ash,and clarifying the applicability of tap water in bio-cement.The relationship between the two and the microstructural properties was investigated using the results of the straight shear test and the permeability test.The results showed that the urease solution prepared with tap water had a more pronounced temperature resistance.The urea concentration and the corresponding pH environment had a direct effect on the urease activity.The calcium carbonate yield was positively correlated with the calcium concentration,and the urea concentration was higher in the ranges of 1.0-1.5 mol/L.As the enzyme-to-gel ratio decreased,the calcium carbonate precipitate produced per unit volume of urease solution gradually converged to a certain value.The shear strength(increased by 37.9%)and permeability(decreased by about 8.9-68.5%)of the modified desert sand peaked with the increase in fly ash content.The microscopic test results indicated that the fly ash could provide nucleation sites for the bio-cement,effectively improving the mechanical properties of the desert sand.The crystal types of calcium carbonate in the modified desert sand were calcite and aragonite,which were the most stable crystal types.This study provides innovative ideas for interdisciplinary research in the fields of bioengineering,ecology and civil engineering.
基金Supported by Teaching Reform Project of Xi’an University of Science and Technology(JG16052 Exploration and Practice of Research-oriented Teaching of Urban Planning Course Based on CIE Comprehensive Cultivation of College Students)
文摘The Science of Land Management is a course integrating theory and practice closely.In order to improve the teaching effect of the course and practice the course,this paper discussed practice work related to main contents of the Science of Land Management.On the basis of taking overall consideration of the status and functions of this course in the entire teaching system,this paper designed three practice teaching parts closely connected with the core contents.This is of realistic significance for improving the teaching quality of the Science of Land Management.
文摘In this paper, 5 high-rise hotels in Xi'an were selected for research, their energy consumption data from 2015 to 2016 were collected and analyzed, their comprehensive energy consumption per unit area was compared by using the standard coal coefficient, and their energy use characteristics and influencing factors were obtained. The test analyzed various parameters of the indoor environment and evaluated the indoor environmental quality according to the specifications and standards. Starting from the perspective of energy use systems, this paper found energy consumption priorities and problems of these hotels, and proposed feasible energy conservation measures, in a view to providing a reference for energy conservation design of high-rise hotels in Xi'an.
基金financially supported by the Natural Science Foundation of China(Grant No.41330315,91214301)the Program of China Geological Survey(Grant No.12120113039900)MOST Special Funds from the State Key Laboratory of Continental Dynamics,Northwest University
文摘The eastern Hexi Corridor Belt（HCB） is located in the transitional belt among the Alxa Block,the Qilian Orogenic Belt and the North China Block. Because of its unique tectonic location, the tectonic setting, provenance, and even the age of the sedimentary strata in the eastern HCB during the Early Paleozoic remain controversial. This study analyzes the provenance of the poorly studied Xiangshan Group, discusses its age of development and tectonic setting in the eastern HCB using a combination of petrological, geochemical and LA-ICP-MS U-Pb zircon dating methods. Based on the youngest age peaks and the fossil evidence, we suggest that the Xiangshan Group is Middle Cambrian to Late Ordovician in age. The complexity of the geochemical characteristics and associated diagrams suggests that the early stage of the Xiangshan Group developed in a passive continental margin environment, late in the backarc basin of the eastern HCB. Based on the sandstone detrital composition, whole-rock geochemistry and detrital zircon ages, we conclude that the Xiangshan Group had an early provenance that was mainly from the Qilian Block and a late provenance from the Qilian Block and the western Alxa Block. The eastern HCB and its northern and southern blocks have similar palaeontology, lithology and basement age characteristics to the South China Block. This indicates that the eastern HCB might not have formed in the intra-continental aulacogen of the North China Block during the Early Paleozoic but has a close affinity to eastern Gondwana.
基金Under the auspices of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA05000000)National Natural Science Foundation of China(No.41271518)Sci-technology Project of Shaanxi Province(No.2013kw19-01)
文摘Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L. （alfalfa） grassland biomass carbon and soil organic carbon density （SOCD） in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period （viz. 0-10 year）. Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0-10 year. During 0-30 year, the SOCD from 0-100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for l0 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.
基金a National Science and Technology Major Special Project of China(Grant No.2016ZX05044)a Postdoctoral Science Foundation of China(Grant No.2018M631181)+3 种基金a Natural Science Foundation of Shaanxi Province of China(Grant No.2019JQ-192)a Special Scientific Research Project of Natural Science of Education Department of Shaanxi Province(Grant No.2020-016)a Foundation Research Project of Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation(Grant No.MTy2019-08)the Independent Projects of the Key Laboratory of Coal Resources Exploration and Comprehensive Utilization,Ministry of Land and Resources of China(Grant No.ZKF2018-1,ZP2018-2).
文摘The methods of nuclear magnetic resonance(NMR)spectroscopy,mercury injection porosimetry(MIP),and gas-water relative permeability(GWRP)were used to reveal the pore structure and permeability characteristics of high-rank coal reservoirs in the Bide-Santang basin,western Guizhou,South China,to provide guidance for coalbed methane(CBM)exploration and exploitation and obtain direct insights for the development of CBM wells.The results indicate that the coal reservoirs in the study area are characterized by well-developed adsorption pores and poorly developed seepage pores.The bimodal NMR transverse relaxation time(T2)spectra and the mutation in the fractal characteristic of the MIP pore volume indicate poor connectivity between the adsorption pores and the seepage pores.As a result,the effective porosity is relatively low,with an average of 1.70%.The irreducible water saturation of the coal reservoir is relatively high,with an average of 66%,leading to a low gas relative permeability under irreducible water saturation.This is the main reason for the low recovery of high-rank CBM reservoirs,and effective enhanced CBM recovery technology urgently is needed.As a nondestructive and less time-consuming technique,the NMR is a promising method to quantitatively characterize the pores and fractures of coals.
基金funded by the National Natural Science Foundation of China(Nos.41807285,41972280,51679117)the National Science Foundation of Jiangxi Province,China(No.20192BAB216034)+1 种基金the China Postdoctoral Science Foundation(Nos.2019M652287,2020T130274)the Jiangxi Provincial Postdoctoral Science Foundation(No.2019KY08)。
文摘In some studies on landslide susceptibility mapping(LSM),landslide boundary and spatial shape characteristics have been expressed in the form of points or circles in the landslide inventory instead of the accurate polygon form.Different expressions of landslide boundaries and spatial shapes may lead to substantial differences in the distribution of predicted landslide susceptibility indexes(LSIs);moreover,the presence of irregular landslide boundaries and spatial shapes introduces uncertainties into the LSM.To address this issue by accurately drawing polygonal boundaries based on LSM,the uncertainty patterns of LSM modelling under two different landslide boundaries and spatial shapes,such as landslide points and circles,are compared.Within the research area of Ruijin City in China,a total of 370 landslides with accurate boundary information are obtained,and 10 environmental factors,such as slope and lithology,are selected.Then,correlation analyses between the landslide boundary shapes and selected environmental factors are performed via the frequency ratio(FR)method.Next,a support vector machine(SVM)and random forest(RF)based on landslide points,circles and accurate landslide polygons are constructed as point-,circle-and polygon-based SVM and RF models,respectively,to address LSM.Finally,the prediction capabilities of the above models are compared by computing their statistical accuracy using receiver operating characteristic analysis,and the uncertainties of the predicted LSIs under the above models are discussed.The results show that using polygonal surfaces with a higher reliability and accuracy to express the landslide boundary and spatial shape can provide a markedly improved LSM accuracy,compared to those based on the points and circles.Moreover,a higher degree of uncertainty of LSM modelling is present in the expression of points because there are too few grid units acting as model input variables.Additionally,the expression of the landslide boundary as circles introduces errors in measurement and is not as accurate as the polygonal boundary in most LSM modelling cases.In addition,the results under different conditions show that the polygon-based models have a higher LSM accuracy,with lower mean values and larger standard deviations compared with the point-and circle-based models.Finally,the overall LSM accuracy of the RF is superior to that of the SVM,and similar patterns of landslide boundary and spatial shape affecting the LSM modelling are reflected in the SVM and RF models.
基金provided by the National Natural Science Foundation of China (Nos.50574072, 50874089 and 50534049)the Special Scientific Foundation of the Shaanxi Department of Education (No.08JK366) is gratefully acknowledged
文摘Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results,we built a thin plate mechanical model for layered and spalled coal bodies.We studied the mechanical mechanism of outbursts,due to instability,of thin plates of coal rocks under the action of in-plane load and normal load,by using the catastrophe theory.The total potential function is derived for the layered rock system,the cusp catastrophe model for the system is established,the bifurcation set that makes the system unstable is given,the process in which gradual change of action forces leads to catastrophic change of state is analyzed,and the effect of movement path of point(P,q) in the control space on the stability of rock plate is analyzed.The study results show that during the process of coal mining,the stability of the layered coal bodies depends not only on its physical properties and dimensions but also on the magnitudes and changing paths of the in-plane load and the normal load.When the gas in the coal bodies ahead of the mining face is pre-drained,the gas pressure can be reduced and the normal load q can be lowered.Consequently,disasters such as coal and gas outbursts can be effectively prevented.
基金This work was supported by the National Natural Science Foundation of China (Nos. 5157-4139 and 5180-4247)De Montfort University through its distinguished Vice-Chancellor 2020 ProgrammeUK Science and Technology Facilities Council (STFC) through Batteries Early Career Researcher Award.
文摘In underground mines, high air temperatures in the summer months lead to an increase in inlet airflow temperatures. This leads to seasonal thermal pollution in the mines. This paper examines the dynamics and effects of seasonal variation in surface air temperatures and surrounding rock temperatures in deep coal mines. It also examines temperature variations in the main ventilation circuit, working face, and surrounding rock. The study results revealed that airflow temperatures were significantly affected by seasonal air temperature variations. The greater the distance was between the inlet and the wellhead of the ventilation shaft, the less the effect was on temperature. Moreover, slight temperature variations (1.0-3.0 ℃) were observed between various points on the return route during the summer months. Airflow temperatures along the airflow inlet to the return route of the working face first decreased, but then increased. The temperature field of the surrounding rock increased gradually with increased distance between the mine roadway and inlet, with recorded rock temperatures as high as 40.53 ℃. The radius of the heat-adjusting layer was between 28 and 33 m.
基金Supported by Natural Science Program of Shaanxi Province Education Department (05JK261)
文摘By solving steady model of air flow diffusion and chemical reaction in loose coal, distribution of oxygen concentration and flow velocity magnitude were obtained. Compared the simulating results with critic value as well as duration of spontaneous combustion from large-scale spontaneous combustion experiment, 'three zones' of spontaneous combustion were partitioned and mining conditions to avoid spontaneous combustion were obtained. The above method was employed to partition 'three zones' in gob of fully mechanized top-coal caving long wall face and got fairly good result. Calculation of the above method is much smaller than simulating the whole process of coal spontaneous combustion, but the prediction precision can satisfy the demand of predicting and extinguishing spontaneous combustion in mining.
基金Funded by the National Natural Science Foundation of China(No.51372197)the Basic Research Plan of Natural Science of Shaanxi Province(No.2020JQ-754)+4 种基金the Key Innovation Team of Shaanxi Province(No.2014KCT-04)the Special Project of Shaanxi Province(No.19JK0490)the Construction and Promotion of Highlevel Achievements in Material Science and Engineering Discipline of Xi’an University of Science and Technology(No.2040519061)the Study on Preparation and Properties of New Solid-wastebased Cementitious Materials(No.6000190120)the Xi’an University of Science and Technology Doctoral Start-up Project(No.2018QDJ011)。
文摘A novel V-doped CeO_(2)-supported alkali-activated-steel-slag-based catalyst(V-CeO_(2)/AC)for photocatalytic decomposition of water to hydrogen was prepared via co-impregnation method.The chemical composition,mineral phase,morphology,and optical performances of the synthesized catalyst samples were characterized by XRF,XRD,SEM,UV-Vis DRS,and so on.XRD and SEM results show that calcium silicate hydrate(Ca1.5SiO3.5·xH2O)mineral phase is formed in the carrier sample,and the prepared catalyst specimens are made up of approximately 50 nm particles.After 6 hours of xenon lamp irradiation,the catalyst supported on V-doped 8wt%CeO_(2) exhibits the highest photocatalytic hydrogen production activity(8292μmol/g),which is attributed to the interaction between the V-doped CeO_(2) active components and FeO existed in catalyst carrier.A possible photocatalytic decomposition of water for hydrogen production mechanism over the V-8CeO_(2)/AC catalyst was proposed.
