The paper analyzes the different characteristics of peasant issues formed by connections between peasants and land at different historical stages,and offers a reference for us to look squarely at peasant issues in the...The paper analyzes the different characteristics of peasant issues formed by connections between peasants and land at different historical stages,and offers a reference for us to look squarely at peasant issues in the reality.The characteristics of peasant issues with land as the inherent feature are:the degree of connection decides the classification and policies of peasants;the private ownership of land decides the political status and influences of peasants;the inherence of private connections with land determines the future of peasants.The characteristics of peasant issues with land as the core value are:the peasant issues with land as the core is the key to victory of new-democratic revolution;the peasant issues with land as the core is the basis of establishment of socialist system;the characteristics of peasant issues with land as the guarantee are:carriers of peasants interests change from unicity to diversity;peasants change from identity certification to vocational certification;the economic influence of peasants changes and penetrates from part to entirety.展开更多
In this paper, based on in-situ observational data of the Coordinated Enhanced Observing Period (CEOP) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau (CAMP-Tibet), structure of the Atmospheric Boundary L...In this paper, based on in-situ observational data of the Coordinated Enhanced Observing Period (CEOP) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau (CAMP-Tibet), structure of the Atmospheric Boundary Layer (ABL) was preliminarily studied during the dry and rainy seasons. The main results show: (a) Diurnal variation of the ABL is obvious over the northern Tibetan Plateau area. The height of the ABL is different with the season change, which ranges from 2,211 m to 4,430 m during the pre-monsoon season and from 1,006 m to 2,212 m during the monsoon season. The ABL height is higher during the dry period than during the rainy period. (b) The humidity is lower during the dry period than during the rainy period, and there are reverse humidity during both periods. (c) Horizontal wind direction is mostly west during the dry period, east under the height of 2,500 m and west above the height of 2,500 m during the rainy period. The wind speed is low during both the rainy and dry periods in the lower ABL layer. The wind speed is stronger within the upper ABL during the dry period than during the rainy period.展开更多
To investigate the influence mechanism of geostress on rockburst characteristics,three groups of gneiss rockburst experiments were conducted under different initial geostress conditions.A high-speed photography system...To investigate the influence mechanism of geostress on rockburst characteristics,three groups of gneiss rockburst experiments were conducted under different initial geostress conditions.A high-speed photography system and acoustic emission(AE)monitoring system were used to monitor the entire rockburst process in real time.The experimental results show that when the initial burial depth increases from 928 m to 1320 m,the proportion of large fracture scale in rockburst increases by 154.54%,and the AE energy increases by 565.63%,reflecting that the degree and severity of rockburst increase with the increase of burial depth.And then,two mechanisms are proposed to explain this effect,including(i)the increase of initial geostress improves the energy storage capacity of gneiss,and then,the excess energy which can be converted into kinetic energy of debris ejection increases,consequently,a more pronounced violent ejection phenomenon is observed at rockburst;(ii)the increase of initial geostress causes more sufficient plate cracks of gneiss after unloading ofσh,which provides a basis for more severe ejection of rockburst.What’s more,a precursor with clear physical meaning for rockburst is proposed under the framework of dynamic response process of crack evolution.Finally,potential value in long term rockburst warning of the precursor obtained in this study is shown via the comparison of conventional precursor.展开更多
The dynamic spalling characteristics of rock are important for stability analysis in rock engineering.This paper presented an experimental investigation on the dynamic spalling characteristics of granite with differen...The dynamic spalling characteristics of rock are important for stability analysis in rock engineering.This paper presented an experimental investigation on the dynamic spalling characteristics of granite with different temperatures and strain rates.A series of dynamic spalling tests with different impact velocities were conducted on thermally treated granite at different temperatures.The dynamic spalling strengths of granite with different temperatures and strain rates were determined.A model was proposed to correlate the dynamic spalling strength of granite,high temperature and strain rate.The results show that the spalling strength of granite decreases with increasing temperature.Moreover,the spalling strength of granite with a higher strain rate is larger than that with a lower strain rate.The proposed model can describe the relationship among dynamic spalling strength of granite,high temperature and strain rate.展开更多
Artificial vegetation restoration is the main measure for vegetation restoration and soil and water conservation in alpine mine dumps on the Qinghai-Tibet Plateau,China.However,there are few reports on the dynamic cha...Artificial vegetation restoration is the main measure for vegetation restoration and soil and water conservation in alpine mine dumps on the Qinghai-Tibet Plateau,China.However,there are few reports on the dynamic changes and the influencing factors of the soil reinforcement effect of plant species after artificial vegetation restoration under different recovery periods.We selected dump areas of the Delni Copper Mine in Qinghai Province,China to study the relationship between the shear strength and the peak displacement of the root-soil composite on the slope during the recovery period,and the influence of the root traits and soil physical properties on the shear resistance characteristics of the root-soil composite via in situ direct shear tests.The results indicate that the shear strength and peak displacement of the rooted soil initially decreased and then increased with the increase of the recovery period.The shear strength of the rooted soil and the recovery period exhibited a quadratic function relationship.There is no significant function relationship between the peak displacement and the recovery period.Significant positive correlations(P<0.05)exists between the shear strength of the root-soil composite and the root biomass density,root volume density,and root area ratio,and they show significant linear correlations(P<0.05).There are no significant correlations(P>0.05)between the shear strength of the root-soil composite and the root length density,and the root volume ratio of the coarse roots to the fine roots.A significant negative linear correlation(P<0.05)exists between the peak displacement of the rooted soil and the coarse-grain content,but no significant correlations(P>0.05)with the root traits,other soil physical property indices(the moisture content and dry density of the soil),and slope gradient.The coarse-grain content is the main factor controlling the peak displacement of the rooted soil.展开更多
Well-developed pores and cracks in coal reservoirs are the main venues for gas storage and migration.To investigate the multi-scale pore fractal characteristics,six coal samples of different rankings were studied usin...Well-developed pores and cracks in coal reservoirs are the main venues for gas storage and migration.To investigate the multi-scale pore fractal characteristics,six coal samples of different rankings were studied using high-pressure mercury injection(HPMI),low-pressure nitrogen adsorption(LPGA-N2),and scanning electron microscopy(SEM)test methods.Based on the Frankel,Halsey and Hill(FHH)fractal theory,the Menger sponge model,Pores and Cracks Analysis System(PCAS),pore volume complexity(D_(v)),coal surface irregularity(Ds)and pore distribution heterogeneity(D_(p))were studied and evaluated,respectively.The effect of three fractal dimensions on the gas adsorption ability was also analyzed with high-pressure isothermal gas adsorption experiments.Results show that pore structures within these coal samples have obvious fractal characteristics.A noticeable segmentation effect appears in the Dv1and Dv2fitting process,with the boundary size ranging from 36.00 to 182.95 nm,which helps differentiate diffusion pores and seepage fractures.The D values show an asymmetric U-shaped trend as the coal metamorphism increases,demonstrating that coalification greatly affects the pore fractal dimensions.The three fractal dimensions can characterize the difference in coal microstructure and reflect their influence on gas adsorption ability.Langmuir volume(V_(L))has an evident and positive correlation with Dsvalues,whereas Langmuir pressure(P_(L))is mainly affected by the combined action of Dvand Dp.This study will provide valuable knowledge for the appraisal of coal seam gas reservoirs of differently ranked coals.展开更多
The grid structure has significant effects on the discharge characteristics of an ion thruster.The discharge performances of a 30 cm diameter ion thruster with flat,convex and concave grids are studied.The analysis re...The grid structure has significant effects on the discharge characteristics of an ion thruster.The discharge performances of a 30 cm diameter ion thruster with flat,convex and concave grids are studied.The analysis results show that the discharge chamber with a convex grid has a larger’magnetic-field free area’than the others,and the parallelism of the magnetic-field isopotential lines and anode is generally the same in the three models.Plasma densities of the three structures at the grid outlet are in the range of 3.1×1016-6.9×1017m-3.Along the thruster axis direction,the electron temperature in the chamber with the convex and concave grids is in the range of 3.3-3.5 eV,while that with a flat grid is lower,in the range of 3.1-3.5 eV.In addition,the convex and the concave grids have better uniform distribution of electron temperature.Moreover,the collision frequency ratios show that the axial degree of ionization of the three models is the highest,and the flat grid has the highest discharge efficiency,followed by the convex grid and the concave grid is the least efficient.The test and simulation results of the 30 cm diameter ion thruster with the convex grid show that the measurement and calculation results are 3.67 A and 3.44 A,respectively,and the error above mainly comes from the ignorance of the doubly charged ions and parameter settings in the model.The comparison error between the simulation and measurement of beam current density is mainly caused by the actual thermal deformation of the grids during the discharge process,which leads to the change in electric potential distribution and variation of the focusing characteristics of the grids.Upon consideration of discharge performance and the thermal grid gap variation,it can be concluded that the flat and concave grids are more suitable for small-diameter ion thrusters,while the convex grid is a more reasonable choice for the higher-power and larger-diameter thrusters.展开更多
The polarization characteristics of ultrathin CsPbBr3nanowires are investigated. Especially, for the height of crosssection of nanowires between 2 nm and 25 nm, the normalized intensity and polarization ratio ρ of Cs...The polarization characteristics of ultrathin CsPbBr3nanowires are investigated. Especially, for the height of crosssection of nanowires between 2 nm and 25 nm, the normalized intensity and polarization ratio ρ of CsPbBr3nanowires with triangular, square and hexagonal cross-section shapes are compared. The results show that, along with the increase of the height of cross-section, the polarization ratios of these three nanowires decrease until T = 15 nm, and increase afterwards.Also, along with the increase of the cross-section area up to 100 nm~2, the polarization ratios of these three nanowires increase too. In general, for the same height or area, the polarization ratio ρ of these nanowires follows ρhexagon> ρsquare>ρtriangle. Therefore, the nanowire with the hexagonal cross-section should be chosen, where for a cross-section height of 2 nm and a length-height ratio of 20 : 1, the maximal polarization ratio is 0.951 at the longitudinal center of the NW. Further,for the hexagonal NW with a cross-section height of 10 nm, the hexagonal NW with a length-height ratio of 45 : 1 exhibits the maximal polarization ratio at the longitudinal center of the NW. These simulation results predict the feasible size and shape of CsPbBr3nanowire devices with high polarization ratios.展开更多
Atmospheric pressure plasma jet shows great potential for polymer film processing. The electrode geometry is the key factor to determine discharge characteristics and film modification of jets. In this paper, we compa...Atmospheric pressure plasma jet shows great potential for polymer film processing. The electrode geometry is the key factor to determine discharge characteristics and film modification of jets. In this paper, we compared the discharge characteristics and the film modifications of atmospheric pressure plasma jets with needle-ring electrode(NRE) and doublering electrode(DRE). The results show that jet with NRE has stronger electric field intensity and higher discharge power,making it present more reactive oxygen particles and higher electron temperature, but its discharge stability is insufficient.In contrast, the jet with DRE has uniform electric field distribution of lower field intensity, which allows it to maintain stable discharge over a wide range of applied voltages. Besides, the modification results show that the treatment efficiency of PET film by NRE is higher than that by DRE. These results provide a suitable atmospheric pressure plasma jets device selection scheme for polymer film processing process.展开更多
Plant tolerance to aluminum(Al)toxicity can be enhanced by an ectomycorrhizal(ECM)fungus through biological filtering or physical blockage.To understand the roles of ECM colonization in Al absorption with regard to Al...Plant tolerance to aluminum(Al)toxicity can be enhanced by an ectomycorrhizal(ECM)fungus through biological filtering or physical blockage.To understand the roles of ECM colonization in Al absorption with regard to Al tolerance,Pinus massoniana seedlings were inoculated with either Lactarius deliciosus(L.:Fr.)Gray isolate 2 or Pisolithus tinctorius(Pers.)Coker et Couch isolate 715 and cultivated in an acid yellow soil with or without 1.0 mM Al^(3+)irrigation for 10 weeks.Biomass production,Al bioaccumulation and transport in seedlings colonized by the two ECM fungi were compared,and the three absorption kinetics(pseudo-first order,pseudo-second order and intraparticle diffusion)models used to evaluate variances in root Al^(3+)absorption capacity.Results show that both fungi increased aboveground biomass and Al tolerance of P.massoniana seedlings,but L.deliciosus 2 was more effective than P.tinctorius 715.Lower Al absorption capacity,fewer available active sites and decreased affinity and boundary layer thickness for Al^(3+),and higher Al accumulation and translocation contributed to the increased Al tolerance in the ECM-inoculated seedlings.These results advance our understanding of the mechanisms and strategies in plant Alto lerance conferred by ECM fungi and show that inoculation with L.deliciosus will better enhance Al tolerance in P.massoniana seedlings used for forest plantation and ecosystem restoration in acidic soils,particularly in Southwest China and similar soils worldwide.展开更多
The key to high-yielding peanut cultivation is the optimization of agricultural production practices.Regulating single-seed precise sowing(SSPS)density and paclobutrazol(Pbz)application concentration are effective pra...The key to high-yielding peanut cultivation is the optimization of agricultural production practices.Regulating single-seed precise sowing(SSPS)density and paclobutrazol(Pbz)application concentration are effective practices that increase peanut yield by improving plant architecture,lodging resistance,and photosynthetic characteristics.Therefore,we conducted a two-factor field optimization experiment for the sowing density(D1:1.95×10^(5)plants ha^(-1),D52:2.40×10plants ha^(-1),D3:2.85×10^(5)plants ha^(-1),and D4:3.30×10^(5)plants ha^(-1))and Pbzapplication concentration(P0:0 mg L^(-1)and P1:100 mg L^(-1)).The objective was to optimize agricultural production practices and provide a theoretical basis for highyielding peanut cultivation by evaluating the effects of sowing density and Pbzapplication on plant architecture,lodging resistance,photosynthetic characteristics,and yield.The results showed that at the same Pbzapplication concentration,increasing sowing density increased lodging percentage and reduced leaf photosynthetic capacity.At the same sowing density,Pbzapplication reduced lodging percentage by decreasing plant height(PH),improving lignin biosynthesis-related enzyme activities,and enhancing stem puncture strength(SPS)and breaking strength(SBS).The paclobutrazol-induced alterations in plant architecture and lodging resistance improved light transmission at the middle and bottom leaf strata,resulting in the increase in relative chlorophyll content and net photosynthetic rate(Pn)of leaves.Furthermore,D3P1treatment had the highest peanut yield among all treatments.In summary,the production strategy combining the sowing density of 2.85×10^(5)plants ha^(-1)with the application of100 mg L^(-1)Pbzwas found to be the optimal agricultural production practice for giving full play to production potential and achieving higher peanut yield.展开更多
This study compares the strength characteristics of rocks anchored by NPR bolts and ordinary bolts with varied preloads,based on the mechanical properties of NPR bolts(with a negative Poisson’s ratio).The results sho...This study compares the strength characteristics of rocks anchored by NPR bolts and ordinary bolts with varied preloads,based on the mechanical properties of NPR bolts(with a negative Poisson’s ratio).The results show that the uniaxial compressive stress-strain curve of ordinary anchored rocks exhibits noticeable abrupt changes.After reaching peak strength,the bolt breaks,whereas the stress-strain curve of NPR-anchored rocks is smoother.The NPR bolt enters the stage of continuous resistance after reaching maximal strength and does not break.As the preload increases,the strength of the anchored rock grows linearly.A calculation equation for the strength of the anchored rock is proposed based on the preload.The theoretical equation fits the test results well,and the fitted parameters show that NPR bolts can better increase the strength of the rock.The concept of dynamic toughness UC of anchored rock is proposed to reflect the comprehensive mechanical properties of anchored rock,including strength and plasticity.As the preload increases,the UC of ordinary anchored rock first decreases and then increases,while the UC of the NPR anchored rock does not change significantly with the preload when the strain is small,and the UC increases with the increase of the preload when the strain is large.展开更多
[Objectives]The paper was to study the fine root distribution characteristics of Populus cathayana plantations at different ages in alpine sandy land.[Methods]With 5,10,15,20,and 25 years old P.cathayana plantation in...[Objectives]The paper was to study the fine root distribution characteristics of Populus cathayana plantations at different ages in alpine sandy land.[Methods]With 5,10,15,20,and 25 years old P.cathayana plantation in the eastern margin of Gonghe Basin,Qinghai Province as the research objects,fine roots were collected by root core drilling method,and the differences of fine root biomass,root length density,average diameter and root tip number at the soil depths of 0-20,20-40,40-60,60-80 and 80-100 cm were analyzed.[Results]The total biomass density of P.cathayana plantation was mainly distributed in the soil layer of 0-60 cm,accounting for 76%of the entire soil layer,and its value increased with the increase in forest age.With the increase in different forest ages,the root length density,average diameter and root tip number of living fine roots in the soil layer of 0-60 cm accounted for 74%-81%of the entire soil layer,and the proportions in the soil layers of 60-80 and 80-100 cm were 9%-11%.The biomass density,root length density,average diameter and root tip number of living and dead fine roots of P.cathayana plantation increased with the increase of forest age.The root length density,average diameter and root tip number of P.cathayana fine roots showed a linear function change trend with the growth of forest age,which could be described by the linear function equation y=ax+b(a>0).The analysis results showed that the root length density,average diameter and root tip number of P.cathayana were significantly correlated with the total biomass density of fine roots,and the root length density and average diameter had an extremely positive correlation with the total biomass density.[Conclusions]In the future,P.cathayana plantation should be properly tended to promote the development of fine roots and maximize its ecological benefits.展开更多
[Objectives]To investigate the effects of different temperature and starvation stress on the expression of AaHsp90 and reveal the molecular mechanism of adaptation to environment in Antheraea assama.[Methods]Taking th...[Objectives]To investigate the effects of different temperature and starvation stress on the expression of AaHsp90 and reveal the molecular mechanism of adaptation to environment in Antheraea assama.[Methods]Taking the normal feeding group at 26℃as the control,the expression change of AaHsp90 was detected by real-time PCR in midgut,fat body and hemlymph after high temperature stress at 38℃,low temperature stress at 4℃and starvation stress separately for different time on the third day of the fifth larvae.[Results]The expression of AaHsp90 in midgut,fat body and hemlymph of Antheraea assama were increased obviously at first and then decreased sharply with the prolongation of treatment time at 38℃.There has a certain inhibitory effect on the expression of AaHsp90 in midgut,fat body and hemolymph after treatment with 4℃for different time.After treatment with starvation,the AaHsp90 expression were increased at 12 and 18 h and decreased sharply at 24 h in midgut,fat body and hemolymph of A.assama.[Conclusions]Comprehensive analysis showed that high temperature and starvation stress can induce the expression of AaHsp90,while low temperature stress mainly suppressed its expression.It was suggested that the AaHsp90 protein may play an important role in the process of adaptation to high temperature and starvation stress in A.assama.展开更多
The compaction characteristics of gravelly soil are affected by gravel hardness.To investigate the evolution and influencing mechanism of different gravel hardness on the compaction characteristics of gravelly soil,he...The compaction characteristics of gravelly soil are affected by gravel hardness.To investigate the evolution and influencing mechanism of different gravel hardness on the compaction characteristics of gravelly soil,heavy compaction tests and crushing tests were conducted on gravelly soils with gravels originated from hard,soft and extremely soft rocks.According to orthogonal experiments and variance analysis,it was found that hardness has a significant impact on the maximum dry density of gravelly soil,followed by gravel content,and lastly,moisture content.For gravel compositions with an average saturated uniaxial compressive strength less than 60 MPa,the order of compacted maximum dry density is soft gravels>hard gravels>extremely soft gravels.Each type of gravelly soil has a threshold for gravel content,with 60%for hard and soft gravels and 50%for extremely soft gravels.Beyond these thresholds,the compacted dry density decreases significantly.There is a certain interaction between hardness,gravel content,and moisture content.Higher hardness increases the influence of gravel content,whereas lower hardness increases the influence of moisture content.Gravelly soils with the coarse aggregate(CA)between 0.7 and 0.8 typically achieve higher dry densities after compaction.In addition,the prediction equations for the particle breakage rate and CA ratio in the Bailey method were proposed to estimate the compaction performance of gravelly soil preliminarily.The results further revealed the compaction mechanism of different gravelly soils and can provide reference for subgrade filling construction.展开更多
Some of the chemical and physical water qualities of the Graff River in the city of Kut were studied, and for two sites of the river, One was at the Crimea site, the other in the Jihad district, and for the period fro...Some of the chemical and physical water qualities of the Graff River in the city of Kut were studied, and for two sites of the river, One was at the Crimea site, the other in the Jihad district, and for the period from October/2018 to March/2019, Seven variables of river water have been analyzed: temperature PH, electrical conductivity, TDS, turbidity, alkaline, and chloride. The results showed that most of the chemical and physical water properties of the river were in normal proportions and did not rise, except for the turbidity, which was at a very high level, and that the pH values were close to the basal side. The results of the statistical analysis revealed positive significant relationships between the pH and (chloride and TDS). On the other hand, between electrical conductivity and both previous variables as well. And a negative significant connection between temperature and alkaline.展开更多
The microscopic characteristics and mechanical properties of rocks change after the action of acid on deep shale,which affects the fracturing effect.Accordingly,we designed and conducted indoor experiments related to ...The microscopic characteristics and mechanical properties of rocks change after the action of acid on deep shale,which affects the fracturing effect.Accordingly,we designed and conducted indoor experiments related to the changes in macro and microscopic characteristics after the interaction of acid with the shale of Wujiaping Formation,based on which the characteristic law of fracture volume modification after acid fracturing was studied using numerical simulation.The results demonstrate that the pores and fractures are enlarged and the structure is significantly loosened after the acid immersion.And a 15%concentration of hydrochloric acid can effectively dissolve shale.Furthermore,the degree of acid-etching reaction is highly variable because of the different carbonate content,which reveals the strong inhomogeneity of the shale system in the Wujiaping Group reservoir section.After the acid interacted with the shale rock samples,the triaxial compressive strength,elastic modulus,and Poisson’s ratio of shale decreased.Moreover,the evaluation of the effect after acid fracturing simulated by fracturing software revealed that the smaller the value of elastic modulus in shale-based reservoirs,the more favorable the fracture volume modification.This discovery not only provides a theoretical basis for the expansion and extension patterns of acid-fracturing in carbonaceous shale formations but also offers research methods and theoretical insights for the fundamental exploration of other deep-seated oil and gas resources.展开更多
Shaped charge warhead is important for enhancing the damage performance of underwater weapons.This paper used finite element analysis software and based on JPC water penetration experiments to examine the influence of...Shaped charge warhead is important for enhancing the damage performance of underwater weapons.This paper used finite element analysis software and based on JPC water penetration experiments to examine the influence of liner parameters(wall thickness,material),charge aspect ratio,and stand-off distance on the movement characteristics of JPC in water.The findings reveal that the head diameter of the JPC increases and experiences significant erosion after entering the water,the effective length of the JPC in water undergoes two distinct phases:a growth phase and a decrease phase,with the velocity of the JPC decaying exponentially.Increasing the liner thickness,stand-off distance and the charge aspect ratio can improve the erosion resistance and the velocity retention capacity of the JPC.The optimal ranges for liner thickness and stand-off distance are 0.0363D_(k) to 0.0545D_(k)(D_(k) is the charge diameter),the stand-off distance should be within 1.0D_(k).After the charge aspect ratio higher than 1.25,the charge structure exerts minimal influence the movement characteristics of the JPC in water.Material density plays a crucial role in the velocity decay pattern of the JPC during penetration.JPC with higher densities exhibit superior velocity retention capabilities in water,with the velocity decay pattern converging if the densities are similar.Consequently,copper,tantalum and tungsten liners are deemed appropriate for underwater shaped charge warhead.Finally,the results will provide an important reference for the design of underwater shaped charge warhead.展开更多
Coal pyrolysis is a fundamental reaction in the thermal processing and utilization of coal.Investigating the behavior and kinetics of coal pyrolysis is crucial for optimizing,designing,and developing a composite riser...Coal pyrolysis is a fundamental reaction in the thermal processing and utilization of coal.Investigating the behavior and kinetics of coal pyrolysis is crucial for optimizing,designing,and developing a composite riser for the staged pyrolysis gasification process of pulverized coal.In this study,the non-isothermal pyrolysis behavior and kinetics of coal were examined at different heating rates(30,50,100,300,500,700,and 900℃/min)using thermogravimetry(TG)coupled with Fourier-transform infrared spectroscopy.Analysis of the TG/derivative TG(TG/DTG)curves indicated that coal pyrolysis mainly occurred between 300℃ and 700℃.Higher heating rates led to more volatiles being released from the coal,and a higher temperature was required to achieve rapid pyrolysis.Kinetic analysis showed that both the model-free methods(Friedman,Flynn-Wall-Ozawa,and Kissinger-Akahira-Sunose)and the model-based method(Coats-Redfern)effectively describe the coal pyrolysis process.The change in the Ea values between the two kinetic models was consistent throughout the pyrolysis process,and the most probable mechanism was the F2 model(secondary chemical reaction).In addition,the heating rate did not change the overall reaction order of the pyrolysis process;however,a higher heating rate resulted in a decrease in the Ea value during the initial pyrolysis stage.展开更多
An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to bal...An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to balance the platform gravity.The two-way blower inflates and deflates the ballonet to regulate the buoyancy.Altitude adjustment is achieved by tracking the differential pressure difference(DPD),and a threshold switching strategy is used to achieve blower flow control.The vertical acceleration regulation ability is decided not only by the blower flow rate,but also by the designed margin of pressure difference(MPD).Pressure difference is a slow-varying variable compared with altitude,and it is adopted as the control variable.The response speed of the actuator to disturbance can be delayed,and the overshoot caused by the large inertia of the platform is inhibited.This method can maintain a high tracking accuracy and reduce the complexity of model calculation,thus improving the robustness of controller design.展开更多
文摘The paper analyzes the different characteristics of peasant issues formed by connections between peasants and land at different historical stages,and offers a reference for us to look squarely at peasant issues in the reality.The characteristics of peasant issues with land as the inherent feature are:the degree of connection decides the classification and policies of peasants;the private ownership of land decides the political status and influences of peasants;the inherence of private connections with land determines the future of peasants.The characteristics of peasant issues with land as the core value are:the peasant issues with land as the core is the key to victory of new-democratic revolution;the peasant issues with land as the core is the basis of establishment of socialist system;the characteristics of peasant issues with land as the guarantee are:carriers of peasants interests change from unicity to diversity;peasants change from identity certification to vocational certification;the economic influence of peasants changes and penetrates from part to entirety.
基金under the auspices of the Chinese National Key Programme for Developing Basic Sciences (2010CB951703)the Chinese National Key Programme for Developing Basic Sciences (2005CB422003)the National Natural Science Foundation of China (41175008, 40810059006 and 40675012)
文摘In this paper, based on in-situ observational data of the Coordinated Enhanced Observing Period (CEOP) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau (CAMP-Tibet), structure of the Atmospheric Boundary Layer (ABL) was preliminarily studied during the dry and rainy seasons. The main results show: (a) Diurnal variation of the ABL is obvious over the northern Tibetan Plateau area. The height of the ABL is different with the season change, which ranges from 2,211 m to 4,430 m during the pre-monsoon season and from 1,006 m to 2,212 m during the monsoon season. The ABL height is higher during the dry period than during the rainy period. (b) The humidity is lower during the dry period than during the rainy period, and there are reverse humidity during both periods. (c) Horizontal wind direction is mostly west during the dry period, east under the height of 2,500 m and west above the height of 2,500 m during the rainy period. The wind speed is low during both the rainy and dry periods in the lower ABL layer. The wind speed is stronger within the upper ABL during the dry period than during the rainy period.
基金support from the National Natural Science Foundation of China(No.41941018,No.52074299)the Fundamental Research Funds for the Central Universities(No.2023JCCXSB02)the China Geological Survey Project(DD20221816,DD20211376)are gratefully acknowledged.
文摘To investigate the influence mechanism of geostress on rockburst characteristics,three groups of gneiss rockburst experiments were conducted under different initial geostress conditions.A high-speed photography system and acoustic emission(AE)monitoring system were used to monitor the entire rockburst process in real time.The experimental results show that when the initial burial depth increases from 928 m to 1320 m,the proportion of large fracture scale in rockburst increases by 154.54%,and the AE energy increases by 565.63%,reflecting that the degree and severity of rockburst increase with the increase of burial depth.And then,two mechanisms are proposed to explain this effect,including(i)the increase of initial geostress improves the energy storage capacity of gneiss,and then,the excess energy which can be converted into kinetic energy of debris ejection increases,consequently,a more pronounced violent ejection phenomenon is observed at rockburst;(ii)the increase of initial geostress causes more sufficient plate cracks of gneiss after unloading ofσh,which provides a basis for more severe ejection of rockburst.What’s more,a precursor with clear physical meaning for rockburst is proposed under the framework of dynamic response process of crack evolution.Finally,potential value in long term rockburst warning of the precursor obtained in this study is shown via the comparison of conventional precursor.
基金supported by the Beijing Natural Science Foundation,China(Grant No.JQ20039)National Natural Science Foundation of China(Grant No.12172019).
文摘The dynamic spalling characteristics of rock are important for stability analysis in rock engineering.This paper presented an experimental investigation on the dynamic spalling characteristics of granite with different temperatures and strain rates.A series of dynamic spalling tests with different impact velocities were conducted on thermally treated granite at different temperatures.The dynamic spalling strengths of granite with different temperatures and strain rates were determined.A model was proposed to correlate the dynamic spalling strength of granite,high temperature and strain rate.The results show that the spalling strength of granite decreases with increasing temperature.Moreover,the spalling strength of granite with a higher strain rate is larger than that with a lower strain rate.The proposed model can describe the relationship among dynamic spalling strength of granite,high temperature and strain rate.
基金supported by the Project of Qinghai Science&Technology Department(Grant No.2021-ZJ-956Q).
文摘Artificial vegetation restoration is the main measure for vegetation restoration and soil and water conservation in alpine mine dumps on the Qinghai-Tibet Plateau,China.However,there are few reports on the dynamic changes and the influencing factors of the soil reinforcement effect of plant species after artificial vegetation restoration under different recovery periods.We selected dump areas of the Delni Copper Mine in Qinghai Province,China to study the relationship between the shear strength and the peak displacement of the root-soil composite on the slope during the recovery period,and the influence of the root traits and soil physical properties on the shear resistance characteristics of the root-soil composite via in situ direct shear tests.The results indicate that the shear strength and peak displacement of the rooted soil initially decreased and then increased with the increase of the recovery period.The shear strength of the rooted soil and the recovery period exhibited a quadratic function relationship.There is no significant function relationship between the peak displacement and the recovery period.Significant positive correlations(P<0.05)exists between the shear strength of the root-soil composite and the root biomass density,root volume density,and root area ratio,and they show significant linear correlations(P<0.05).There are no significant correlations(P>0.05)between the shear strength of the root-soil composite and the root length density,and the root volume ratio of the coarse roots to the fine roots.A significant negative linear correlation(P<0.05)exists between the peak displacement of the rooted soil and the coarse-grain content,but no significant correlations(P>0.05)with the root traits,other soil physical property indices(the moisture content and dry density of the soil),and slope gradient.The coarse-grain content is the main factor controlling the peak displacement of the rooted soil.
基金The first author would like to express sincere appreciation for the scholarship provided by China Scholarship Council(No.202006430006)and University of Wollongongfinancially supported by the ACARP Project C28006+1 种基金the National Key Research and Development Program of China(No.2018YFC0808301)the Natural Science Foundation of Beijing Municipality,China(No.8192036)。
文摘Well-developed pores and cracks in coal reservoirs are the main venues for gas storage and migration.To investigate the multi-scale pore fractal characteristics,six coal samples of different rankings were studied using high-pressure mercury injection(HPMI),low-pressure nitrogen adsorption(LPGA-N2),and scanning electron microscopy(SEM)test methods.Based on the Frankel,Halsey and Hill(FHH)fractal theory,the Menger sponge model,Pores and Cracks Analysis System(PCAS),pore volume complexity(D_(v)),coal surface irregularity(Ds)and pore distribution heterogeneity(D_(p))were studied and evaluated,respectively.The effect of three fractal dimensions on the gas adsorption ability was also analyzed with high-pressure isothermal gas adsorption experiments.Results show that pore structures within these coal samples have obvious fractal characteristics.A noticeable segmentation effect appears in the Dv1and Dv2fitting process,with the boundary size ranging from 36.00 to 182.95 nm,which helps differentiate diffusion pores and seepage fractures.The D values show an asymmetric U-shaped trend as the coal metamorphism increases,demonstrating that coalification greatly affects the pore fractal dimensions.The three fractal dimensions can characterize the difference in coal microstructure and reflect their influence on gas adsorption ability.Langmuir volume(V_(L))has an evident and positive correlation with Dsvalues,whereas Langmuir pressure(P_(L))is mainly affected by the combined action of Dvand Dp.This study will provide valuable knowledge for the appraisal of coal seam gas reservoirs of differently ranked coals.
基金National Natural Science Foundation of China(No.61901202)Key Laboratory Funds for the Science and Technology on Vacuum Technology and Physics Laboratory,Lanzhou Institute of Physics(No.HTKJ2019KL510003)。
文摘The grid structure has significant effects on the discharge characteristics of an ion thruster.The discharge performances of a 30 cm diameter ion thruster with flat,convex and concave grids are studied.The analysis results show that the discharge chamber with a convex grid has a larger’magnetic-field free area’than the others,and the parallelism of the magnetic-field isopotential lines and anode is generally the same in the three models.Plasma densities of the three structures at the grid outlet are in the range of 3.1×1016-6.9×1017m-3.Along the thruster axis direction,the electron temperature in the chamber with the convex and concave grids is in the range of 3.3-3.5 eV,while that with a flat grid is lower,in the range of 3.1-3.5 eV.In addition,the convex and the concave grids have better uniform distribution of electron temperature.Moreover,the collision frequency ratios show that the axial degree of ionization of the three models is the highest,and the flat grid has the highest discharge efficiency,followed by the convex grid and the concave grid is the least efficient.The test and simulation results of the 30 cm diameter ion thruster with the convex grid show that the measurement and calculation results are 3.67 A and 3.44 A,respectively,and the error above mainly comes from the ignorance of the doubly charged ions and parameter settings in the model.The comparison error between the simulation and measurement of beam current density is mainly caused by the actual thermal deformation of the grids during the discharge process,which leads to the change in electric potential distribution and variation of the focusing characteristics of the grids.Upon consideration of discharge performance and the thermal grid gap variation,it can be concluded that the flat and concave grids are more suitable for small-diameter ion thrusters,while the convex grid is a more reasonable choice for the higher-power and larger-diameter thrusters.
文摘The polarization characteristics of ultrathin CsPbBr3nanowires are investigated. Especially, for the height of crosssection of nanowires between 2 nm and 25 nm, the normalized intensity and polarization ratio ρ of CsPbBr3nanowires with triangular, square and hexagonal cross-section shapes are compared. The results show that, along with the increase of the height of cross-section, the polarization ratios of these three nanowires decrease until T = 15 nm, and increase afterwards.Also, along with the increase of the cross-section area up to 100 nm~2, the polarization ratios of these three nanowires increase too. In general, for the same height or area, the polarization ratio ρ of these nanowires follows ρhexagon> ρsquare>ρtriangle. Therefore, the nanowire with the hexagonal cross-section should be chosen, where for a cross-section height of 2 nm and a length-height ratio of 20 : 1, the maximal polarization ratio is 0.951 at the longitudinal center of the NW. Further,for the hexagonal NW with a cross-section height of 10 nm, the hexagonal NW with a length-height ratio of 45 : 1 exhibits the maximal polarization ratio at the longitudinal center of the NW. These simulation results predict the feasible size and shape of CsPbBr3nanowire devices with high polarization ratios.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11565003)the Jiangxi Province Academic Degree and Postgraduate Education and Teaching Reform Research Project (Grant No. JXYJG-2022-180)the Scientific Research Base Project of Gannan Normal University (Grant No. 22wdxt01)。
文摘Atmospheric pressure plasma jet shows great potential for polymer film processing. The electrode geometry is the key factor to determine discharge characteristics and film modification of jets. In this paper, we compared the discharge characteristics and the film modifications of atmospheric pressure plasma jets with needle-ring electrode(NRE) and doublering electrode(DRE). The results show that jet with NRE has stronger electric field intensity and higher discharge power,making it present more reactive oxygen particles and higher electron temperature, but its discharge stability is insufficient.In contrast, the jet with DRE has uniform electric field distribution of lower field intensity, which allows it to maintain stable discharge over a wide range of applied voltages. Besides, the modification results show that the treatment efficiency of PET film by NRE is higher than that by DRE. These results provide a suitable atmospheric pressure plasma jets device selection scheme for polymer film processing process.
基金supported by the National Natural Science Foundation of China (31570599 and 32171753)。
文摘Plant tolerance to aluminum(Al)toxicity can be enhanced by an ectomycorrhizal(ECM)fungus through biological filtering or physical blockage.To understand the roles of ECM colonization in Al absorption with regard to Al tolerance,Pinus massoniana seedlings were inoculated with either Lactarius deliciosus(L.:Fr.)Gray isolate 2 or Pisolithus tinctorius(Pers.)Coker et Couch isolate 715 and cultivated in an acid yellow soil with or without 1.0 mM Al^(3+)irrigation for 10 weeks.Biomass production,Al bioaccumulation and transport in seedlings colonized by the two ECM fungi were compared,and the three absorption kinetics(pseudo-first order,pseudo-second order and intraparticle diffusion)models used to evaluate variances in root Al^(3+)absorption capacity.Results show that both fungi increased aboveground biomass and Al tolerance of P.massoniana seedlings,but L.deliciosus 2 was more effective than P.tinctorius 715.Lower Al absorption capacity,fewer available active sites and decreased affinity and boundary layer thickness for Al^(3+),and higher Al accumulation and translocation contributed to the increased Al tolerance in the ECM-inoculated seedlings.These results advance our understanding of the mechanisms and strategies in plant Alto lerance conferred by ECM fungi and show that inoculation with L.deliciosus will better enhance Al tolerance in P.massoniana seedlings used for forest plantation and ecosystem restoration in acidic soils,particularly in Southwest China and similar soils worldwide.
基金supported by the National Key Research and Development Program of China(2020YFD1000902)the Shandong Key Research and Development Program(2018YFJH0601-3)+1 种基金the Major Agricultural Applied Technological Innovation Projects in Shandong Province(SD2019ZZ11)the Shandong Modern Agricultural Technology and Industry System(SDAIT-04-01)。
文摘The key to high-yielding peanut cultivation is the optimization of agricultural production practices.Regulating single-seed precise sowing(SSPS)density and paclobutrazol(Pbz)application concentration are effective practices that increase peanut yield by improving plant architecture,lodging resistance,and photosynthetic characteristics.Therefore,we conducted a two-factor field optimization experiment for the sowing density(D1:1.95×10^(5)plants ha^(-1),D52:2.40×10plants ha^(-1),D3:2.85×10^(5)plants ha^(-1),and D4:3.30×10^(5)plants ha^(-1))and Pbzapplication concentration(P0:0 mg L^(-1)and P1:100 mg L^(-1)).The objective was to optimize agricultural production practices and provide a theoretical basis for highyielding peanut cultivation by evaluating the effects of sowing density and Pbzapplication on plant architecture,lodging resistance,photosynthetic characteristics,and yield.The results showed that at the same Pbzapplication concentration,increasing sowing density increased lodging percentage and reduced leaf photosynthetic capacity.At the same sowing density,Pbzapplication reduced lodging percentage by decreasing plant height(PH),improving lignin biosynthesis-related enzyme activities,and enhancing stem puncture strength(SPS)and breaking strength(SBS).The paclobutrazol-induced alterations in plant architecture and lodging resistance improved light transmission at the middle and bottom leaf strata,resulting in the increase in relative chlorophyll content and net photosynthetic rate(Pn)of leaves.Furthermore,D3P1treatment had the highest peanut yield among all treatments.In summary,the production strategy combining the sowing density of 2.85×10^(5)plants ha^(-1)with the application of100 mg L^(-1)Pbzwas found to be the optimal agricultural production practice for giving full play to production potential and achieving higher peanut yield.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174096 and 51874311)。
文摘This study compares the strength characteristics of rocks anchored by NPR bolts and ordinary bolts with varied preloads,based on the mechanical properties of NPR bolts(with a negative Poisson’s ratio).The results show that the uniaxial compressive stress-strain curve of ordinary anchored rocks exhibits noticeable abrupt changes.After reaching peak strength,the bolt breaks,whereas the stress-strain curve of NPR-anchored rocks is smoother.The NPR bolt enters the stage of continuous resistance after reaching maximal strength and does not break.As the preload increases,the strength of the anchored rock grows linearly.A calculation equation for the strength of the anchored rock is proposed based on the preload.The theoretical equation fits the test results well,and the fitted parameters show that NPR bolts can better increase the strength of the rock.The concept of dynamic toughness UC of anchored rock is proposed to reflect the comprehensive mechanical properties of anchored rock,including strength and plasticity.As the preload increases,the UC of ordinary anchored rock first decreases and then increases,while the UC of the NPR anchored rock does not change significantly with the preload when the strain is small,and the UC increases with the increase of the preload when the strain is large.
文摘[Objectives]The paper was to study the fine root distribution characteristics of Populus cathayana plantations at different ages in alpine sandy land.[Methods]With 5,10,15,20,and 25 years old P.cathayana plantation in the eastern margin of Gonghe Basin,Qinghai Province as the research objects,fine roots were collected by root core drilling method,and the differences of fine root biomass,root length density,average diameter and root tip number at the soil depths of 0-20,20-40,40-60,60-80 and 80-100 cm were analyzed.[Results]The total biomass density of P.cathayana plantation was mainly distributed in the soil layer of 0-60 cm,accounting for 76%of the entire soil layer,and its value increased with the increase in forest age.With the increase in different forest ages,the root length density,average diameter and root tip number of living fine roots in the soil layer of 0-60 cm accounted for 74%-81%of the entire soil layer,and the proportions in the soil layers of 60-80 and 80-100 cm were 9%-11%.The biomass density,root length density,average diameter and root tip number of living and dead fine roots of P.cathayana plantation increased with the increase of forest age.The root length density,average diameter and root tip number of P.cathayana fine roots showed a linear function change trend with the growth of forest age,which could be described by the linear function equation y=ax+b(a>0).The analysis results showed that the root length density,average diameter and root tip number of P.cathayana were significantly correlated with the total biomass density of fine roots,and the root length density and average diameter had an extremely positive correlation with the total biomass density.[Conclusions]In the future,P.cathayana plantation should be properly tended to promote the development of fine roots and maximize its ecological benefits.
基金Supported by Special Basic Cooperative Research Programs of Yunnan Provincial Undergraduate Universities Association (2021BA070001-070)Yunnan Fundamental Research Projects (202201AT070226).
文摘[Objectives]To investigate the effects of different temperature and starvation stress on the expression of AaHsp90 and reveal the molecular mechanism of adaptation to environment in Antheraea assama.[Methods]Taking the normal feeding group at 26℃as the control,the expression change of AaHsp90 was detected by real-time PCR in midgut,fat body and hemlymph after high temperature stress at 38℃,low temperature stress at 4℃and starvation stress separately for different time on the third day of the fifth larvae.[Results]The expression of AaHsp90 in midgut,fat body and hemlymph of Antheraea assama were increased obviously at first and then decreased sharply with the prolongation of treatment time at 38℃.There has a certain inhibitory effect on the expression of AaHsp90 in midgut,fat body and hemolymph after treatment with 4℃for different time.After treatment with starvation,the AaHsp90 expression were increased at 12 and 18 h and decreased sharply at 24 h in midgut,fat body and hemolymph of A.assama.[Conclusions]Comprehensive analysis showed that high temperature and starvation stress can induce the expression of AaHsp90,while low temperature stress mainly suppressed its expression.It was suggested that the AaHsp90 protein may play an important role in the process of adaptation to high temperature and starvation stress in A.assama.
基金supported by the National Natural Science Foundation of China(No.51878127)the Fundamental Research Funds for the Central Universities(N180104013).
文摘The compaction characteristics of gravelly soil are affected by gravel hardness.To investigate the evolution and influencing mechanism of different gravel hardness on the compaction characteristics of gravelly soil,heavy compaction tests and crushing tests were conducted on gravelly soils with gravels originated from hard,soft and extremely soft rocks.According to orthogonal experiments and variance analysis,it was found that hardness has a significant impact on the maximum dry density of gravelly soil,followed by gravel content,and lastly,moisture content.For gravel compositions with an average saturated uniaxial compressive strength less than 60 MPa,the order of compacted maximum dry density is soft gravels>hard gravels>extremely soft gravels.Each type of gravelly soil has a threshold for gravel content,with 60%for hard and soft gravels and 50%for extremely soft gravels.Beyond these thresholds,the compacted dry density decreases significantly.There is a certain interaction between hardness,gravel content,and moisture content.Higher hardness increases the influence of gravel content,whereas lower hardness increases the influence of moisture content.Gravelly soils with the coarse aggregate(CA)between 0.7 and 0.8 typically achieve higher dry densities after compaction.In addition,the prediction equations for the particle breakage rate and CA ratio in the Bailey method were proposed to estimate the compaction performance of gravelly soil preliminarily.The results further revealed the compaction mechanism of different gravelly soils and can provide reference for subgrade filling construction.
文摘Some of the chemical and physical water qualities of the Graff River in the city of Kut were studied, and for two sites of the river, One was at the Crimea site, the other in the Jihad district, and for the period from October/2018 to March/2019, Seven variables of river water have been analyzed: temperature PH, electrical conductivity, TDS, turbidity, alkaline, and chloride. The results showed that most of the chemical and physical water properties of the river were in normal proportions and did not rise, except for the turbidity, which was at a very high level, and that the pH values were close to the basal side. The results of the statistical analysis revealed positive significant relationships between the pH and (chloride and TDS). On the other hand, between electrical conductivity and both previous variables as well. And a negative significant connection between temperature and alkaline.
基金This study is supported by a Scientific Research Project of Sinopec(Program No.P21087-2)the Open Fund of Key Laboratory of Marine Oil&Gas Reservoirs Production,Sinopec(Grant No.33550000-22-FW2099-0004).
文摘The microscopic characteristics and mechanical properties of rocks change after the action of acid on deep shale,which affects the fracturing effect.Accordingly,we designed and conducted indoor experiments related to the changes in macro and microscopic characteristics after the interaction of acid with the shale of Wujiaping Formation,based on which the characteristic law of fracture volume modification after acid fracturing was studied using numerical simulation.The results demonstrate that the pores and fractures are enlarged and the structure is significantly loosened after the acid immersion.And a 15%concentration of hydrochloric acid can effectively dissolve shale.Furthermore,the degree of acid-etching reaction is highly variable because of the different carbonate content,which reveals the strong inhomogeneity of the shale system in the Wujiaping Group reservoir section.After the acid interacted with the shale rock samples,the triaxial compressive strength,elastic modulus,and Poisson’s ratio of shale decreased.Moreover,the evaluation of the effect after acid fracturing simulated by fracturing software revealed that the smaller the value of elastic modulus in shale-based reservoirs,the more favorable the fracture volume modification.This discovery not only provides a theoretical basis for the expansion and extension patterns of acid-fracturing in carbonaceous shale formations but also offers research methods and theoretical insights for the fundamental exploration of other deep-seated oil and gas resources.
基金supported by the National Natural Science Foundation of China(Grant No.11672278)。
文摘Shaped charge warhead is important for enhancing the damage performance of underwater weapons.This paper used finite element analysis software and based on JPC water penetration experiments to examine the influence of liner parameters(wall thickness,material),charge aspect ratio,and stand-off distance on the movement characteristics of JPC in water.The findings reveal that the head diameter of the JPC increases and experiences significant erosion after entering the water,the effective length of the JPC in water undergoes two distinct phases:a growth phase and a decrease phase,with the velocity of the JPC decaying exponentially.Increasing the liner thickness,stand-off distance and the charge aspect ratio can improve the erosion resistance and the velocity retention capacity of the JPC.The optimal ranges for liner thickness and stand-off distance are 0.0363D_(k) to 0.0545D_(k)(D_(k) is the charge diameter),the stand-off distance should be within 1.0D_(k).After the charge aspect ratio higher than 1.25,the charge structure exerts minimal influence the movement characteristics of the JPC in water.Material density plays a crucial role in the velocity decay pattern of the JPC during penetration.JPC with higher densities exhibit superior velocity retention capabilities in water,with the velocity decay pattern converging if the densities are similar.Consequently,copper,tantalum and tungsten liners are deemed appropriate for underwater shaped charge warhead.Finally,the results will provide an important reference for the design of underwater shaped charge warhead.
基金the financial support from the National Natural Science Foundation of China(Grant No.21576293 and 21576294)。
文摘Coal pyrolysis is a fundamental reaction in the thermal processing and utilization of coal.Investigating the behavior and kinetics of coal pyrolysis is crucial for optimizing,designing,and developing a composite riser for the staged pyrolysis gasification process of pulverized coal.In this study,the non-isothermal pyrolysis behavior and kinetics of coal were examined at different heating rates(30,50,100,300,500,700,and 900℃/min)using thermogravimetry(TG)coupled with Fourier-transform infrared spectroscopy.Analysis of the TG/derivative TG(TG/DTG)curves indicated that coal pyrolysis mainly occurred between 300℃ and 700℃.Higher heating rates led to more volatiles being released from the coal,and a higher temperature was required to achieve rapid pyrolysis.Kinetic analysis showed that both the model-free methods(Friedman,Flynn-Wall-Ozawa,and Kissinger-Akahira-Sunose)and the model-based method(Coats-Redfern)effectively describe the coal pyrolysis process.The change in the Ea values between the two kinetic models was consistent throughout the pyrolysis process,and the most probable mechanism was the F2 model(secondary chemical reaction).In addition,the heating rate did not change the overall reaction order of the pyrolysis process;however,a higher heating rate resulted in a decrease in the Ea value during the initial pyrolysis stage.
基金the National Natural Science Foundation of China(No.52175103)。
文摘An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to balance the platform gravity.The two-way blower inflates and deflates the ballonet to regulate the buoyancy.Altitude adjustment is achieved by tracking the differential pressure difference(DPD),and a threshold switching strategy is used to achieve blower flow control.The vertical acceleration regulation ability is decided not only by the blower flow rate,but also by the designed margin of pressure difference(MPD).Pressure difference is a slow-varying variable compared with altitude,and it is adopted as the control variable.The response speed of the actuator to disturbance can be delayed,and the overshoot caused by the large inertia of the platform is inhibited.This method can maintain a high tracking accuracy and reduce the complexity of model calculation,thus improving the robustness of controller design.
