Microwave(MW)drying method was adopted to enhance the liquid permeability of Scots pine lumber.Structure changes were characterized by stereoscope microscope,scanned electron microscope(SEM)and transmission electron m...Microwave(MW)drying method was adopted to enhance the liquid permeability of Scots pine lumber.Structure changes were characterized by stereoscope microscope,scanned electron microscope(SEM)and transmission electron microscope(TEM)examination.Pore parameters before and after MW treatment were detected by mercury intrusion porosimetry(MIP)method,and the effect of structure changes on liquid permeability were analyzed.As stereoscope microscope,SEM and TEM examination results showed,macro and micro checks mainly developed at intercellcular of tracheids,intercellular of ray parenchyma and tracheid,while these checks extend main along the radial-longitudinal plane.Pit border destruction,aspirated pits’orus translocation and micro-checks in tracheid cell wall were also observed.MIP test shown that pore volume and pore area increased as macro and micro checks generated to form new cavities.Microstructure changes would increase the quantity of pores or enlarge the pore diameter.Liquid flow pathways increased as macro and micro checks generated,aspirated pits reopened to form new pathways;liquid flow efficiency improved as porosity,pore volume and pore diameter increased which facilitated the liquid flow.展开更多
The purpose of the present paper is to study and develop indicators and procedures for the evaluation of genetic structure changes in germplasm conservation due to social and natural environment reasons. Some basic ...The purpose of the present paper is to study and develop indicators and procedures for the evaluation of genetic structure changes in germplasm conservation due to social and natural environment reasons. Some basic concepts in germplasm study were introduced at first. Then, six kinds of indicators for genetic diversity as a measure of genetic potential of a germplasm collection were presented, i.e., numbers of different entities at certain level, evenness of the entity distribution, genetic similarity and genetic distance, genetic variance and genetic coefficient of variation, multivariate genetic variation indices, and coefficient of parentage. It was pointed out that genetic dispersion did not provide a complete concept of genetic diversity if without any information from genetic richness. Based on the above, the indicators for genetic erosion as the genetic structure changes of germplasm conservation due to social reasons, the indicators of genetic vulnerability as the genetic structure changes of germplasm conservation due to environmental stresses, the measurement of genetic drift and genetic shift as the genetic structure changes of germplasm collection during reproduction or seed increase were reviewed and developed. Furthermore, the estimation procedures of the indicators by using molecular markers were suggested. Finally, the case studies on suitable conservation sample size of self-pollinated and open-pollinated populations were given for reference.展开更多
Conductive polymer composites based on crystalline polymer matrix have been prepared by using an in-situ polymerization process of pyrrole in amorphous poly (ethylene terephthalate) (PET) film. The DSC and WAXD me...Conductive polymer composites based on crystalline polymer matrix have been prepared by using an in-situ polymerization process of pyrrole in amorphous poly (ethylene terephthalate) (PET) film. The DSC and WAXD measurement and SEM observation show that liquid-induced crystallization of PET matrix has occurred during the preparation of composite films. Depending upon the equilibrium degree of swelling and crystallinity, the limited depth of penetration of pyrrole molecules results in a skin-core structure of the composite film. The skin layer containing charge transfer intercalated polypyrrole has a surface resistance of 3.5×10;Ω. Rigid and heat-resistant polypyrrole molecules formed in PET film increase the tensile modulus and, especially, the rigidity of PET at elevated temperatures. However, they decrease the tensile strength and elongation at break, and impair the thermal ductility of PET.展开更多
ased on the most recent data from the 1990 census, this paper analyses the trend of the changing household size and structure, and the socioeconomic causes beginning in the 1950s. The relationship between the househol...ased on the most recent data from the 1990 census, this paper analyses the trend of the changing household size and structure, and the socioeconomic causes beginning in the 1950s. The relationship between the household size and structure and China's population policy is also analyzed in the paper. Two different categories of socioeconomic factors have been identified which operate in opposition to each other, influencing the increase and decrease in the desirability of co-residence of domestic groups. The future household size and structure is determined by both of them.展开更多
China's crop structure has undergone significant changes in the last two decades since 2000,with an increase in the share of cereals,vegetables,and fruit,squeezing out other crops.As a result,land productivity,nut...China's crop structure has undergone significant changes in the last two decades since 2000,with an increase in the share of cereals,vegetables,and fruit,squeezing out other crops.As a result,land productivity,nutrient supply,and carbon emissions have changed.How to reallocate limited farmland among crops to achieve the multiple goals of agrifood systems becomes an important issue.This study explores the sources of land productivity and nutrition supply growth and carbon emissions reduction,and identifies the multiple roles of crop structural change from 2003 to 2020 based on a decomposition analysis.The results reveal that the growth within crops is still the primary driver in land productivity and nutrition supply and the reduction in carbon emissions.However,structural change also plays various roles at different periods.From 2003 to 2010,crop structural change increased the total calorie supply but lowered land productivity and contributed at least 70%of the total growth of carbon emissions.The crop structure was relatively stable,and their effects were modest from 2010 to 2015.From 2015 to 2020,the crop structural change began to play a greater role and generate synergistic effects in improving land productivity,micronutrient supply,and reducing carbon emissions,contributing to approximately a quarter of the growth of land productivity and 30%of total carbon emissions reduction.These results suggest that strategies for crop structural change should comprehensively consider its multiple impacts,aiming to achieve co-benefits while minimizing trade-offs.展开更多
Climate warming profoundly affects plant biodiversity, community productivity, and soil properties in alpine and subalpine grassland ecosystems. However, these effects are poorly understood across elevational gradient...Climate warming profoundly affects plant biodiversity, community productivity, and soil properties in alpine and subalpine grassland ecosystems. However, these effects are poorly understood across elevational gradients in subalpine meadow ecosystems. To reveal the elevational patterns of warming effects on plant biodiversity, community structure, productivity, and soil properties, we conducted a warming experiment using open-top chambers from August 2019 to August 2022 at high(2764 m a. s. l.), medium(2631 m a. s. l.), and low(2544 m a. s. l.) elevational gradients on a subalpine meadow slope of Mount Wutai, Northern China. Our results showed that three years of warming significantly increased topsoil temperature but significantly decreased topsoil moisture at all elevations(P<0.05), and the percentage of increasing temperature and decreasing moisture both gradually raised with elevation lifting. Warming-induced decreasing proportions of soil organic carbon(SOC, by 19.24%), and total nitrogen(TN, by 24.56%) were the greatest at high elevational gradients. Experimental warming did not affect topsoil C: N, p H, NO_(3)^(-)-N, or NH_(4)^(+)-N at the three elevational gradients. Warming significantly increased species richness(P<0.01) and Shannon-Weiner index(P<0.05) at low elevational gradients but significantly decreased belowground biomass(P<0.05) at a depth of 0–10 cm at three elevational gradients. Warming caused significant increases in the aboveground biomass in the three elevational plots. Warming significantly increased the aboveground biomass of graminoids in medium(by 92.47%) and low(by 98.25%) elevational gradients, that of sedges in high(by 72.44%) and medium(by 57.16%) elevational plots, and that of forbs in high(by 75.88%), medium(by 34.38%), and low(by 74.95%) elevational plots. Species richness had significant linear correlations with SOC, TN, and C: N(P<0.05), but significant nonlinear responses to soil temperature and soil moisture in the warmed treatment(P<0.05). The warmed aboveground biomass had a significant nonlinear response to soil temperature and significant linear responses to soil moisture(P<0.05). This study provided evidence that altitude is a factor in sensitivity to climate warming, and these different parameters(e.g., plant species richness, Shannon-Weiner index, soil temperature, soil moisture, SOC, and TN) can be used to measure this sensitivity.展开更多
Lithium cobalt oxide(LCO)is the dominating cathode materials for lithium-ion batteries(LIBs)deployed in consumer electronic devices for its superior volumetric energy density and electrochemical performances.The const...Lithium cobalt oxide(LCO)is the dominating cathode materials for lithium-ion batteries(LIBs)deployed in consumer electronic devices for its superior volumetric energy density and electrochemical performances.The constantly increasing demands of higher energy density urge to develop high-voltage LCO via a variety of strategies.However,the corresponding modification mechanism,especially the influence of the long-and short-range structural transitions at high-voltage on electrochemical performance,is still not well understood and needs further exploration.Based on ss-NMR,in-situ X-ray diffraction,and electrochemical performance results,it is revealed that the H3 to H1-3 phase transition dictates the structural reversibility and stability of LCO,thereby determining the electrochemical performance.The introduction of La and Al ions could postpone the appearance of H1-3 phase and induce various types of local environments to alleviate the volume variation at the atomic level,leading to better reversibility of the H1-3 phase and smaller lattice strain,and significantly improved cycle performance.Such a comprehensive long-range,local,and electronic structure characterization enables an in-depth understanding of the structural evolution of LCO,providing a guiding principle for developing high-voltage LCO for high energy density LIBs.展开更多
In this paper,the effects of sea spray on tropical cyclone(TC)structure and intensity variation are evaluated through numerical simulations using an advanced sea-spray parameterization from the National Oceanic and At...In this paper,the effects of sea spray on tropical cyclone(TC)structure and intensity variation are evaluated through numerical simulations using an advanced sea-spray parameterization from the National Oceanic and Atmospheric Administration/Earth System Research Laboratory(NOAA/ESRL),which is incorporated in the idealized Advanced Research version of the Weather Research and Forecast (WRF-ARW)model.The effect of sea spray on TC boundary-layer structure is also analyzed.The results show that there is a significant increase in TC intensity when its boundary-layer wind includes the radial and tangential winds,their structure change,and the total surface wind speed change.Diagnosis of the vorticity budget shows that an increase of convergence in TC boundary layer enhances TC vorticity due to the dynamic effect of sea spay.The main kinematic effect of the friction velocity reduction by sea spray produces an increment of large-scale convergence in the TC boundary layer,while the radial and tangential winds significantly increase with an increment of the horizontal gradient maximum of the radial wind, resulting in a final increase in the simulated TC intensity.The surface enthalpy flux enlarges TC intensity and reduces storm structure change to some degree,which results in a secondary thermodynamic impact on TC intensification.Implications of the new interpretation of sea-spray effects on TC intensification are also discussed.展开更多
Applications of multifractal analysis to white matter structure changes on magnetic resonance imaging(MRI) have recently received increasing attentions. Although some progresses have been made, there is no evident s...Applications of multifractal analysis to white matter structure changes on magnetic resonance imaging(MRI) have recently received increasing attentions. Although some progresses have been made, there is no evident study on applying multifractal analysis to evaluate the white matter structural changes on MRI for Alzheimer's disease(AD) research. In this paper, to explore multifractal analysis of white matter structural changes on 3D MRI volumes between normal aging and early AD, we not only extend the traditional box-counting multifractal analysis(BCMA) into the 3D case, but also propose a modified integer ratio based BCMA(IRBCMA) algorithm to compensate for the rigid division rule in BCMA. We verify multifractal characteristics in 3D white matter MRI volumes. In addition to the previously well studied multifractal feature,△α, we also demonstrated △ f as an alternative and effective multifractal feature to distinguish NC from AD subjects.Both △α and △ f are found to have strong positive correlation with the clinical MMSE scores with statistical significance.Moreover, the proposed IRBCMA can be an alternative and more accurate algorithm for 3D volume analysis. Our findings highlight the potential usefulness of multifractal analysis, which may contribute to clarify some aspects of the etiology of AD through detection of structural changes in white matter.展开更多
s—Suzhou Wuxi Changzhou Region (Su Xi Chang) is a famous prosperous agricultural region in China. Since the early 1980s agriculture in Su Xi Chang has got constant developed, but its growth rate is lower than t...s—Suzhou Wuxi Changzhou Region (Su Xi Chang) is a famous prosperous agricultural region in China. Since the early 1980s agriculture in Su Xi Chang has got constant developed, but its growth rate is lower than the provincial average level of Jiangsu, and its structure has not changed much. Therefore it lost many in the position of agricultural areal division of labour within Jiangsu Province. The authors of this paper suggest that Su Xi Chang agriculture should perform multiple social, economic and ecological functions with the suburban and export oriented farming as the main development direction. It is also necessary to improve management and organization structure for enhancing Su Xi Chang agricultural vitality.展开更多
Supercapacitors,or electric double-layer capacitors(EDLCs),are the new generation of energy storage devices to store electrical charges and provide high power densities and long cyclic life compared to other storage d...Supercapacitors,or electric double-layer capacitors(EDLCs),are the new generation of energy storage devices to store electrical charges and provide high power densities and long cyclic life compared to other storage devices.EDLC mainly consists of activated carbon electrodes and an electrolyte,and the performance of EDLC depends on the activated carbon electrodes.In this work,the structural changes of activated carbon electrodes are analyzed using commercial 2.7 V/9500F EDLCs in its manufacturing process.It is found that there is no significant change in morphology and crystal structure of the activated carbon,but its specific surface area(SSA)reduced greatly.The SSA of activated carbon was decreased by 23%after they were manufactured or converted into electrodes and finally retained only 40%of SSA after the capacitance test.Besides,the SSA of the positive electrodes was found to decrease critically than that of the negative electrodes.The SSA of the external positive electrodes is only 14.3%after fl oating test at 65℃.展开更多
In order to provide scientific information on the prevention and treatment of silicosis,studies about changes of silicotic collagen in lungs were carried out. In this paper, we present experiments about the structural...In order to provide scientific information on the prevention and treatment of silicosis,studies about changes of silicotic collagen in lungs were carried out. In this paper, we present experiments about the structural changes of collagen in silicotic lungs of rats and patients. These included electron microscopy, circular dichroism and infrared spectroscopy studies of collagen fibers. The results indicated that fibers of silicotic collagen were shorter in length, smaller in diameter and decreased in α-helix content. The -Si-O-R- group and -OH group were found increased and -C-C- backbone shortened. The increase of -Si-O-R-group indicated that silica formed linking bridges between collagens which may be the cause of progressive enlargement of nodules展开更多
The shrink fit retaining ring is currently the easiest to install and the most widely used end fixed for structure AC excitation variable speed generator-motor rotor end windings.However,the current research on the ef...The shrink fit retaining ring is currently the easiest to install and the most widely used end fixed for structure AC excitation variable speed generator-motor rotor end windings.However,the current research on the effect of high strength sealing on the ventilation and heat dissipation performance of the end is not enough.In this paper,based on the actual structural parameters and periodic symmetry simplification,the three-dimensional coupled calculation model of fluid field and temperature field is established.After solving the fluid and thermal equations,the influence of the length of rotor support block,the height of rotor support block,and the number of rotor support block on the fluid flow and temperature distribution in the rotor end region of generator-motor is studied using the finite volume method.The rheological characteristics of the air in the rotor domain,such as velocity and inter-winding flow,are analyzed.The law of temperature variation with local structure in the computational domain is studied.The variation law of cooling medium performance inside the large variable speed power generator motor is revealed.展开更多
Iron-nitride films were prepared by reactive sputtering, and the effect of annealing treatment on the structures was investigated by means of in-situ electron microscopy and high resolution electron microscopy (HREM)....Iron-nitride films were prepared by reactive sputtering, and the effect of annealing treatment on the structures was investigated by means of in-situ electron microscopy and high resolution electron microscopy (HREM). As-deposited films were observed to be a mixed structure of a few ultrafine epsilon-Fe2-3N particles existing in the amorphous matrix. it was found that the structure-relaxation in the amorphous occurred at 473 K, and the ultrafine grains began to grow at the higher annealing temperatures. The transition of the amorphous to epsilon-Fe2-3N was almost completed at 673 K. It is considered that the formation of the ideal epsilon-Fe3N is originated from the ordering of the nitrogen atoms during the annealing in vacuum. On the other hand, gamma'-phase (Fe4N) was seen to precipitation of epsilon-phase at 723 K. Two possible modes are proposed in the precipitation of gamma'-phase, depending on the heating rate and crystallographic orientation relationships, i.e. [121](epsilon)//[001](gamma), (2(1) over bar0$)(epsilon)//(110)(gamma) and [100](epsilon)//[110](gamma), (001)(epsilon)//(111)(gamma). In addition, alpha-Fe particles were observed to form from the gamma'-phase at high temperatures. We assumed that these structural changes are due to the diffusion of nitrogen and iron atoms during the annealing, except for the case of the precipitation of the gamma'-phase as depicted above. The results obtained in this work are in a good agreement with the assumption.展开更多
The rapid growth of infrastructure investment is a salient feature of China’s economy since the reform and opening-up in 1978,contributing to not only the aggregate demand but also the structural change and productiv...The rapid growth of infrastructure investment is a salient feature of China’s economy since the reform and opening-up in 1978,contributing to not only the aggregate demand but also the structural change and productivity growth on the supply-side.This paper builds a multi-sector general equilibrium model to show how infrastructure investment influences structural change through price,investment and income effects,and influences productivity growth through the intensive and extensive marginal effects.By quantifying the model with China’s economy for the period 1981-2017,the paper finds that the infrastructure investment restrained the rise of services,but boosted productivity growth over the period.The policy implication is that China should ramp up infrastructure investment to increase productivity as it pursues high-quality development,but give priority to new infrastructure and public-interest infrastructure to promote industrial structural upgrade.展开更多
The crystal of aconitine has been obtained through an unexpected spontaneous change of the solid power of aconitine in air and characterized by single-crystal X-ray diffraction analysis and elemental analysis. Crystal...The crystal of aconitine has been obtained through an unexpected spontaneous change of the solid power of aconitine in air and characterized by single-crystal X-ray diffraction analysis and elemental analysis. Crystallographic data: orthorhombic, space group P2_12_12_1 with a = 17.0745(6), b = 15.5990(6), c = 12.2443(6) ?, V = 3261.2(2) ?~3, Z = 4, C_(34)H_(47)NO_(11), M_r = 645.73, D_c = 1.315 g/cm^3, F(000) = 1384, μ(MoKa) = 0.098 mm^(-1), R = 0.0605 and wR = 0.1311. Aconitine is diester diterpenoid alkaloid, and its main structure is composed of four six-membered and two five-membered rings. The intramolecular and intermolecular O–H···O and C–H···O hydrogen bonds extend the adjacent molecules into a one-dimensional chain and a two-dimensional framework, which may be the essential reason for the change.展开更多
Investigation that protein oxidation to the formation of advanced glycation end products(AGEs)after chicken myofibrillar protein glycation is limited.Models of protein oxidation induced by different concentrations of ...Investigation that protein oxidation to the formation of advanced glycation end products(AGEs)after chicken myofibrillar protein glycation is limited.Models of protein oxidation induced by different concentrations of hydroxyl radicals(·OH)were developed after the chicken myofibrillar protein mild glycation(MPG).Results exhibited that levels of AGEs and surface hydrophobicity(H_(0))steadily increased with the a ddition of h ydrogen peroxide(H_(2)O_(2))concentration.However,levels of s ulfhydryl group,free amino group,and particle size gradually decreased with the H_(2)O_(2)concentration.The protein carbonyl value increased in H_(2)O_(2)concentration until 10 mmol/L.Pearson's correlation indicated that MPG structure modification(unfolding and degradation)induced by protein oxidation were significantly positively correlated with AGEs concentration(P<0.05).Finally,a mechanism was proposed to hypothesize t he effect of protein oxidation on the formation of AGEs under MPG conditions.展开更多
Marine biodiversity is changing in response to altered physical environment, subsequent ecological changes as well as anthropogenic disturbances. In this study, phytoplankton samples in situ collected in the Bering Se...Marine biodiversity is changing in response to altered physical environment, subsequent ecological changes as well as anthropogenic disturbances. In this study, phytoplankton samples in situ collected in the Bering Sea in July of 1999 and 2010 were analyzed to obtain phytoplankton community structure and spatial-temporal variation between the beginning and end of this decade, and the correlation of phytoplankton community dynamics and environmental factors was investigated. A total of 5 divisions, 58 genera and 153 species of phytoplankton belonging to 3 ecological groups were identified. The vast majority of phytoplankton consisted of diatoms accounting for 66.7% of the total species and 95.2% of the total abundance. Considering differentiation in spatial extent and phytoplankton sample types, there were subtle changes in species composition, large altering in abundance and significant variation in spatial distribution between two surveys. The abundance peak area was located at the Bering Strait while sub peak was found at the Bering Sea Basin. The boreal-temperate diatom was the dominant flora, which was subsequently replaced by eurythermal and frigid-water diatom. Phytoplankton community in the Bering Sea was not a simplex uniform community but composed of deep-ocean assemblage and neritic assemblage. The deep-ocean assemblage was located in the northwestern Pacific Ocean and Bering Sea Basin, dominated by boreal-temperate species(Neodenticula seminae, Thalassiothrix longissima, Amphiprora hyperborean, Chaetoceros atlanticus, Thalassiosira trifulta, etc.) and eurychoric species(Thalassionema nitzschioides, Ch. compressus, Rhizosolenia styliformis, etc.), and characterized by low abundance, even interspecies abundance allocations, diverse dominant species and high species diversity. The neritic assemblage was distributed on the continental shelf and slope of Bering Sea and was mainly composed of frigid-water species(Th.nordenski?ldii, Ch. furcellatus, Ch. socialis, Bacteriosira fragilis, etc.) and eurythermal and euryhaline species(L.danicus, Ch. curvisetus, Coscinodiscus curvatulus, etc.), and it was characterized by high abundance, uneven interspecies allocations, prominent dominant species and low species diversity. Spatial-temporal variation of species composition and abundance of phytoplankton in the Bering Sea was directly controlled by surface circulation,nutrient supply and ice edge.展开更多
基金supported by Key Research&Development Program of Zhejiang Province(2021C02012)Chinese National Natural Science Foundation,Study on Pore Structure and Liquid Permeate Mechanism of Moso Bamboo(31700489).
文摘Microwave(MW)drying method was adopted to enhance the liquid permeability of Scots pine lumber.Structure changes were characterized by stereoscope microscope,scanned electron microscope(SEM)and transmission electron microscope(TEM)examination.Pore parameters before and after MW treatment were detected by mercury intrusion porosimetry(MIP)method,and the effect of structure changes on liquid permeability were analyzed.As stereoscope microscope,SEM and TEM examination results showed,macro and micro checks mainly developed at intercellcular of tracheids,intercellular of ray parenchyma and tracheid,while these checks extend main along the radial-longitudinal plane.Pit border destruction,aspirated pits’orus translocation and micro-checks in tracheid cell wall were also observed.MIP test shown that pore volume and pore area increased as macro and micro checks generated to form new cavities.Microstructure changes would increase the quantity of pores or enlarge the pore diameter.Liquid flow pathways increased as macro and micro checks generated,aspirated pits reopened to form new pathways;liquid flow efficiency improved as porosity,pore volume and pore diameter increased which facilitated the liquid flow.
基金supported by the National Natural Science Foundation of China(30270805 and 30490250)Doctorate Foundation of Higher Education(20020307028).
文摘The purpose of the present paper is to study and develop indicators and procedures for the evaluation of genetic structure changes in germplasm conservation due to social and natural environment reasons. Some basic concepts in germplasm study were introduced at first. Then, six kinds of indicators for genetic diversity as a measure of genetic potential of a germplasm collection were presented, i.e., numbers of different entities at certain level, evenness of the entity distribution, genetic similarity and genetic distance, genetic variance and genetic coefficient of variation, multivariate genetic variation indices, and coefficient of parentage. It was pointed out that genetic dispersion did not provide a complete concept of genetic diversity if without any information from genetic richness. Based on the above, the indicators for genetic erosion as the genetic structure changes of germplasm conservation due to social reasons, the indicators of genetic vulnerability as the genetic structure changes of germplasm conservation due to environmental stresses, the measurement of genetic drift and genetic shift as the genetic structure changes of germplasm collection during reproduction or seed increase were reviewed and developed. Furthermore, the estimation procedures of the indicators by using molecular markers were suggested. Finally, the case studies on suitable conservation sample size of self-pollinated and open-pollinated populations were given for reference.
文摘Conductive polymer composites based on crystalline polymer matrix have been prepared by using an in-situ polymerization process of pyrrole in amorphous poly (ethylene terephthalate) (PET) film. The DSC and WAXD measurement and SEM observation show that liquid-induced crystallization of PET matrix has occurred during the preparation of composite films. Depending upon the equilibrium degree of swelling and crystallinity, the limited depth of penetration of pyrrole molecules results in a skin-core structure of the composite film. The skin layer containing charge transfer intercalated polypyrrole has a surface resistance of 3.5×10;Ω. Rigid and heat-resistant polypyrrole molecules formed in PET film increase the tensile modulus and, especially, the rigidity of PET at elevated temperatures. However, they decrease the tensile strength and elongation at break, and impair the thermal ductility of PET.
文摘ased on the most recent data from the 1990 census, this paper analyses the trend of the changing household size and structure, and the socioeconomic causes beginning in the 1950s. The relationship between the household size and structure and China's population policy is also analyzed in the paper. Two different categories of socioeconomic factors have been identified which operate in opposition to each other, influencing the increase and decrease in the desirability of co-residence of domestic groups. The future household size and structure is determined by both of them.
基金This work was supported by the National Natural Science Foundation of China(72061147002 and 72373143)the National Social Science Fund of China(22&ZD085).
文摘China's crop structure has undergone significant changes in the last two decades since 2000,with an increase in the share of cereals,vegetables,and fruit,squeezing out other crops.As a result,land productivity,nutrient supply,and carbon emissions have changed.How to reallocate limited farmland among crops to achieve the multiple goals of agrifood systems becomes an important issue.This study explores the sources of land productivity and nutrition supply growth and carbon emissions reduction,and identifies the multiple roles of crop structural change from 2003 to 2020 based on a decomposition analysis.The results reveal that the growth within crops is still the primary driver in land productivity and nutrition supply and the reduction in carbon emissions.However,structural change also plays various roles at different periods.From 2003 to 2010,crop structural change increased the total calorie supply but lowered land productivity and contributed at least 70%of the total growth of carbon emissions.The crop structure was relatively stable,and their effects were modest from 2010 to 2015.From 2015 to 2020,the crop structural change began to play a greater role and generate synergistic effects in improving land productivity,micronutrient supply,and reducing carbon emissions,contributing to approximately a quarter of the growth of land productivity and 30%of total carbon emissions reduction.These results suggest that strategies for crop structural change should comprehensively consider its multiple impacts,aiming to achieve co-benefits while minimizing trade-offs.
基金carried out in the framework of the 1331 Project of Cultural Ecology Collaborative Innovation Center in Wutai Mountain (00000342)co-financed by Program for the Philosophy and Social Sciences Research of Higher Learning Institutions of Shanxi (2022J027)+1 种基金Applied Basic Research Project of Shanxi Province (202203021221225)Basic Research Project of Xinzhou Science and Technology Bureau (20230501)。
文摘Climate warming profoundly affects plant biodiversity, community productivity, and soil properties in alpine and subalpine grassland ecosystems. However, these effects are poorly understood across elevational gradients in subalpine meadow ecosystems. To reveal the elevational patterns of warming effects on plant biodiversity, community structure, productivity, and soil properties, we conducted a warming experiment using open-top chambers from August 2019 to August 2022 at high(2764 m a. s. l.), medium(2631 m a. s. l.), and low(2544 m a. s. l.) elevational gradients on a subalpine meadow slope of Mount Wutai, Northern China. Our results showed that three years of warming significantly increased topsoil temperature but significantly decreased topsoil moisture at all elevations(P<0.05), and the percentage of increasing temperature and decreasing moisture both gradually raised with elevation lifting. Warming-induced decreasing proportions of soil organic carbon(SOC, by 19.24%), and total nitrogen(TN, by 24.56%) were the greatest at high elevational gradients. Experimental warming did not affect topsoil C: N, p H, NO_(3)^(-)-N, or NH_(4)^(+)-N at the three elevational gradients. Warming significantly increased species richness(P<0.01) and Shannon-Weiner index(P<0.05) at low elevational gradients but significantly decreased belowground biomass(P<0.05) at a depth of 0–10 cm at three elevational gradients. Warming caused significant increases in the aboveground biomass in the three elevational plots. Warming significantly increased the aboveground biomass of graminoids in medium(by 92.47%) and low(by 98.25%) elevational gradients, that of sedges in high(by 72.44%) and medium(by 57.16%) elevational plots, and that of forbs in high(by 75.88%), medium(by 34.38%), and low(by 74.95%) elevational plots. Species richness had significant linear correlations with SOC, TN, and C: N(P<0.05), but significant nonlinear responses to soil temperature and soil moisture in the warmed treatment(P<0.05). The warmed aboveground biomass had a significant nonlinear response to soil temperature and significant linear responses to soil moisture(P<0.05). This study provided evidence that altitude is a factor in sensitivity to climate warming, and these different parameters(e.g., plant species richness, Shannon-Weiner index, soil temperature, soil moisture, SOC, and TN) can be used to measure this sensitivity.
基金funded by the National Natural Science Foundation of China(grant no.21761132030,21935009)National Key Research and Development Program of China(grant no.2016YFB0901502,2018YFB0905400)Collaboration project between Ningde City&Xiamen University(2017c002)。
文摘Lithium cobalt oxide(LCO)is the dominating cathode materials for lithium-ion batteries(LIBs)deployed in consumer electronic devices for its superior volumetric energy density and electrochemical performances.The constantly increasing demands of higher energy density urge to develop high-voltage LCO via a variety of strategies.However,the corresponding modification mechanism,especially the influence of the long-and short-range structural transitions at high-voltage on electrochemical performance,is still not well understood and needs further exploration.Based on ss-NMR,in-situ X-ray diffraction,and electrochemical performance results,it is revealed that the H3 to H1-3 phase transition dictates the structural reversibility and stability of LCO,thereby determining the electrochemical performance.The introduction of La and Al ions could postpone the appearance of H1-3 phase and induce various types of local environments to alleviate the volume variation at the atomic level,leading to better reversibility of the H1-3 phase and smaller lattice strain,and significantly improved cycle performance.Such a comprehensive long-range,local,and electronic structure characterization enables an in-depth understanding of the structural evolution of LCO,providing a guiding principle for developing high-voltage LCO for high energy density LIBs.
基金the National Natural Science Foundation of China (Grant No.30070606) and Graduate Cultivation Foundation of Beijing Forestry University(Grant No.304)
基金National Basic Research Program of China(973 Program)(2009CB421500)Natural Science Foundation of China(40875039,40730948,40921160381)Projects for Public Welfare(Meteorology)of China (GYHY201006008)
文摘In this paper,the effects of sea spray on tropical cyclone(TC)structure and intensity variation are evaluated through numerical simulations using an advanced sea-spray parameterization from the National Oceanic and Atmospheric Administration/Earth System Research Laboratory(NOAA/ESRL),which is incorporated in the idealized Advanced Research version of the Weather Research and Forecast (WRF-ARW)model.The effect of sea spray on TC boundary-layer structure is also analyzed.The results show that there is a significant increase in TC intensity when its boundary-layer wind includes the radial and tangential winds,their structure change,and the total surface wind speed change.Diagnosis of the vorticity budget shows that an increase of convergence in TC boundary layer enhances TC vorticity due to the dynamic effect of sea spay.The main kinematic effect of the friction velocity reduction by sea spray produces an increment of large-scale convergence in the TC boundary layer,while the radial and tangential winds significantly increase with an increment of the horizontal gradient maximum of the radial wind, resulting in a final increase in the simulated TC intensity.The surface enthalpy flux enlarges TC intensity and reduces storm structure change to some degree,which results in a secondary thermodynamic impact on TC intensification.Implications of the new interpretation of sea-spray effects on TC intensification are also discussed.
基金Project supported by the National Natural Science Foundation of China(Grant No.61271079)the Vice Chancellor Research Grant in University of Wollongongthe Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Applications of multifractal analysis to white matter structure changes on magnetic resonance imaging(MRI) have recently received increasing attentions. Although some progresses have been made, there is no evident study on applying multifractal analysis to evaluate the white matter structural changes on MRI for Alzheimer's disease(AD) research. In this paper, to explore multifractal analysis of white matter structural changes on 3D MRI volumes between normal aging and early AD, we not only extend the traditional box-counting multifractal analysis(BCMA) into the 3D case, but also propose a modified integer ratio based BCMA(IRBCMA) algorithm to compensate for the rigid division rule in BCMA. We verify multifractal characteristics in 3D white matter MRI volumes. In addition to the previously well studied multifractal feature,△α, we also demonstrated △ f as an alternative and effective multifractal feature to distinguish NC from AD subjects.Both △α and △ f are found to have strong positive correlation with the clinical MMSE scores with statistical significance.Moreover, the proposed IRBCMA can be an alternative and more accurate algorithm for 3D volume analysis. Our findings highlight the potential usefulness of multifractal analysis, which may contribute to clarify some aspects of the etiology of AD through detection of structural changes in white matter.
文摘s—Suzhou Wuxi Changzhou Region (Su Xi Chang) is a famous prosperous agricultural region in China. Since the early 1980s agriculture in Su Xi Chang has got constant developed, but its growth rate is lower than the provincial average level of Jiangsu, and its structure has not changed much. Therefore it lost many in the position of agricultural areal division of labour within Jiangsu Province. The authors of this paper suggest that Su Xi Chang agriculture should perform multiple social, economic and ecological functions with the suburban and export oriented farming as the main development direction. It is also necessary to improve management and organization structure for enhancing Su Xi Chang agricultural vitality.
基金the Major Special Projects of the Plan“Science and Technology Innovation 2025”in Ningbo(No.2019B10045)the Key Project of CRRC(No.2019CKB198).
文摘Supercapacitors,or electric double-layer capacitors(EDLCs),are the new generation of energy storage devices to store electrical charges and provide high power densities and long cyclic life compared to other storage devices.EDLC mainly consists of activated carbon electrodes and an electrolyte,and the performance of EDLC depends on the activated carbon electrodes.In this work,the structural changes of activated carbon electrodes are analyzed using commercial 2.7 V/9500F EDLCs in its manufacturing process.It is found that there is no significant change in morphology and crystal structure of the activated carbon,but its specific surface area(SSA)reduced greatly.The SSA of activated carbon was decreased by 23%after they were manufactured or converted into electrodes and finally retained only 40%of SSA after the capacitance test.Besides,the SSA of the positive electrodes was found to decrease critically than that of the negative electrodes.The SSA of the external positive electrodes is only 14.3%after fl oating test at 65℃.
文摘In order to provide scientific information on the prevention and treatment of silicosis,studies about changes of silicotic collagen in lungs were carried out. In this paper, we present experiments about the structural changes of collagen in silicotic lungs of rats and patients. These included electron microscopy, circular dichroism and infrared spectroscopy studies of collagen fibers. The results indicated that fibers of silicotic collagen were shorter in length, smaller in diameter and decreased in α-helix content. The -Si-O-R- group and -OH group were found increased and -C-C- backbone shortened. The increase of -Si-O-R-group indicated that silica formed linking bridges between collagens which may be the cause of progressive enlargement of nodules
基金This research was funded by Dongfang Electric Machinery Co., Ltd.
文摘The shrink fit retaining ring is currently the easiest to install and the most widely used end fixed for structure AC excitation variable speed generator-motor rotor end windings.However,the current research on the effect of high strength sealing on the ventilation and heat dissipation performance of the end is not enough.In this paper,based on the actual structural parameters and periodic symmetry simplification,the three-dimensional coupled calculation model of fluid field and temperature field is established.After solving the fluid and thermal equations,the influence of the length of rotor support block,the height of rotor support block,and the number of rotor support block on the fluid flow and temperature distribution in the rotor end region of generator-motor is studied using the finite volume method.The rheological characteristics of the air in the rotor domain,such as velocity and inter-winding flow,are analyzed.The law of temperature variation with local structure in the computational domain is studied.The variation law of cooling medium performance inside the large variable speed power generator motor is revealed.
文摘Iron-nitride films were prepared by reactive sputtering, and the effect of annealing treatment on the structures was investigated by means of in-situ electron microscopy and high resolution electron microscopy (HREM). As-deposited films were observed to be a mixed structure of a few ultrafine epsilon-Fe2-3N particles existing in the amorphous matrix. it was found that the structure-relaxation in the amorphous occurred at 473 K, and the ultrafine grains began to grow at the higher annealing temperatures. The transition of the amorphous to epsilon-Fe2-3N was almost completed at 673 K. It is considered that the formation of the ideal epsilon-Fe3N is originated from the ordering of the nitrogen atoms during the annealing in vacuum. On the other hand, gamma'-phase (Fe4N) was seen to precipitation of epsilon-phase at 723 K. Two possible modes are proposed in the precipitation of gamma'-phase, depending on the heating rate and crystallographic orientation relationships, i.e. [121](epsilon)//[001](gamma), (2(1) over bar0$)(epsilon)//(110)(gamma) and [100](epsilon)//[110](gamma), (001)(epsilon)//(111)(gamma). In addition, alpha-Fe particles were observed to form from the gamma'-phase at high temperatures. We assumed that these structural changes are due to the diffusion of nitrogen and iron atoms during the annealing, except for the case of the precipitation of the gamma'-phase as depicted above. The results obtained in this work are in a good agreement with the assumption.
基金supported by the National Natural Science Foundation of China(NSFC)General Program(Grant No.71973156)the Natural Science Foundation of Guangdong Province General Program(Grant No.2019A1515011287)。
文摘The rapid growth of infrastructure investment is a salient feature of China’s economy since the reform and opening-up in 1978,contributing to not only the aggregate demand but also the structural change and productivity growth on the supply-side.This paper builds a multi-sector general equilibrium model to show how infrastructure investment influences structural change through price,investment and income effects,and influences productivity growth through the intensive and extensive marginal effects.By quantifying the model with China’s economy for the period 1981-2017,the paper finds that the infrastructure investment restrained the rise of services,but boosted productivity growth over the period.The policy implication is that China should ramp up infrastructure investment to increase productivity as it pursues high-quality development,but give priority to new infrastructure and public-interest infrastructure to promote industrial structural upgrade.
基金Supported by the Scientific Research Project of Education Department of Shaanxi Provincial Government in 2014(No.14JK1045)the key project of Baoji University of Arts and Sciences in 2014(No.ZK14009)
文摘The crystal of aconitine has been obtained through an unexpected spontaneous change of the solid power of aconitine in air and characterized by single-crystal X-ray diffraction analysis and elemental analysis. Crystallographic data: orthorhombic, space group P2_12_12_1 with a = 17.0745(6), b = 15.5990(6), c = 12.2443(6) ?, V = 3261.2(2) ?~3, Z = 4, C_(34)H_(47)NO_(11), M_r = 645.73, D_c = 1.315 g/cm^3, F(000) = 1384, μ(MoKa) = 0.098 mm^(-1), R = 0.0605 and wR = 0.1311. Aconitine is diester diterpenoid alkaloid, and its main structure is composed of four six-membered and two five-membered rings. The intramolecular and intermolecular O–H···O and C–H···O hydrogen bonds extend the adjacent molecules into a one-dimensional chain and a two-dimensional framework, which may be the essential reason for the change.
基金supported by National Key R&D Program of China(2021YFD2100104)griculture Research System of China(CARS-41-Z)+2 种基金Science and Technology Project of Nanjing City(202002040)Jiangsu Province Policy Guidance Program(BX2020008)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX21_0579),China。
文摘Investigation that protein oxidation to the formation of advanced glycation end products(AGEs)after chicken myofibrillar protein glycation is limited.Models of protein oxidation induced by different concentrations of hydroxyl radicals(·OH)were developed after the chicken myofibrillar protein mild glycation(MPG).Results exhibited that levels of AGEs and surface hydrophobicity(H_(0))steadily increased with the a ddition of h ydrogen peroxide(H_(2)O_(2))concentration.However,levels of s ulfhydryl group,free amino group,and particle size gradually decreased with the H_(2)O_(2)concentration.The protein carbonyl value increased in H_(2)O_(2)concentration until 10 mmol/L.Pearson's correlation indicated that MPG structure modification(unfolding and degradation)induced by protein oxidation were significantly positively correlated with AGEs concentration(P<0.05).Finally,a mechanism was proposed to hypothesize t he effect of protein oxidation on the formation of AGEs under MPG conditions.
基金The National Natural Science Foundation of China under contract Nos 41306116 and 41506217the Basic Research of the National Department of Science and Technology under contract No.GASI-01-02-04the Polar Science Strategic Research Foundation of China under contract No.20140309
文摘Marine biodiversity is changing in response to altered physical environment, subsequent ecological changes as well as anthropogenic disturbances. In this study, phytoplankton samples in situ collected in the Bering Sea in July of 1999 and 2010 were analyzed to obtain phytoplankton community structure and spatial-temporal variation between the beginning and end of this decade, and the correlation of phytoplankton community dynamics and environmental factors was investigated. A total of 5 divisions, 58 genera and 153 species of phytoplankton belonging to 3 ecological groups were identified. The vast majority of phytoplankton consisted of diatoms accounting for 66.7% of the total species and 95.2% of the total abundance. Considering differentiation in spatial extent and phytoplankton sample types, there were subtle changes in species composition, large altering in abundance and significant variation in spatial distribution between two surveys. The abundance peak area was located at the Bering Strait while sub peak was found at the Bering Sea Basin. The boreal-temperate diatom was the dominant flora, which was subsequently replaced by eurythermal and frigid-water diatom. Phytoplankton community in the Bering Sea was not a simplex uniform community but composed of deep-ocean assemblage and neritic assemblage. The deep-ocean assemblage was located in the northwestern Pacific Ocean and Bering Sea Basin, dominated by boreal-temperate species(Neodenticula seminae, Thalassiothrix longissima, Amphiprora hyperborean, Chaetoceros atlanticus, Thalassiosira trifulta, etc.) and eurychoric species(Thalassionema nitzschioides, Ch. compressus, Rhizosolenia styliformis, etc.), and characterized by low abundance, even interspecies abundance allocations, diverse dominant species and high species diversity. The neritic assemblage was distributed on the continental shelf and slope of Bering Sea and was mainly composed of frigid-water species(Th.nordenski?ldii, Ch. furcellatus, Ch. socialis, Bacteriosira fragilis, etc.) and eurythermal and euryhaline species(L.danicus, Ch. curvisetus, Coscinodiscus curvatulus, etc.), and it was characterized by high abundance, uneven interspecies allocations, prominent dominant species and low species diversity. Spatial-temporal variation of species composition and abundance of phytoplankton in the Bering Sea was directly controlled by surface circulation,nutrient supply and ice edge.