Plants require a number of essential elements in different proportions for ensuring their growth and development.The elemental concentrations in leaves reflect the functions and adaptations of plants under specific en...Plants require a number of essential elements in different proportions for ensuring their growth and development.The elemental concentrations in leaves reflect the functions and adaptations of plants under specific environmental conditions.However,less is known about how the spectrum of leaf elements associated with resource acquisition,photosynthesis and growth regulates forest biomass along broad elevational gradients.We examined the influence of leaf element distribution and diversity on forest biomass by analyzing ten elements(C,N,P,K,Ca,Mg,Zn,Fe,Cu,and Mn)in tree communities situated every 100 meters along an extensive elevation gradient,ranging from the tropical forest(80 meters above sea level)to the alpine treeline(4200 meters above sea level)in the Kangchenjunga Landscape in eastern Nepal Himalayas.We calculated communityweighted averages(reflecting dominant traits governing biomass,i.e.,mass-ratio effect)and functional divergence(reflecting increased trait variety,i.e.,complementarity effect)for leaf elements in a total of 1,859 trees representing 116 species.An increasing mass-ratio effect and decreasing complementarity in leaf elements enhance forest biomass accumulation.A combination of elements together with elevation explains biomass(52.2%of the variance)better than individual elemental trait diversity(0.05%to 21%of the variance).Elevation modulates trait diversity among plant species in biomass accumulation.Complementarity promotes biomass at lower elevations,but reduces biomass at higher elevations,demonstrating an interaction between elevation and complementarity.The interaction between elevation and mass-ratio effect produces heterogeneous effects on biomass along the elevation gradient.Our research indicates that biomass accumulation can be disproportionately affected by elevation due to interactions among trait diversities across vegetation zones.While higher trait variation enhances the adaptation of species to environmental changes,it reduces biomass accumulation,especially at higher elevations.展开更多
The problem of hydrodynamics of the three-leaf dislocated floating-ring bearing was studied by means of boundary element method.The law including the distribution of pressure on boundary surface(axial,bearing and floa...The problem of hydrodynamics of the three-leaf dislocated floating-ring bearing was studied by means of boundary element method.The law including the distribution of pressure on boundary surface(axial,bearing and floating-ring)and its friction loss in different eccentricities was obtained.The results show that the inner friction of three-leaf dislocated bearing increases from 390.875to 1 091.65,and the inner friction of three-leaf dislocated floating-ring bearing increases from 94.2523to 114.5069with eccentricity varying from 0to 0.075in nondimensional.So changing the pressure and flow field of bearing by adding floating-ring is more stability and less wasted work of friction than three-leaf dislocated bearing.展开更多
Altitude affects leaf stoichiometry by regulating temperature and precipitation,and influencing soil properties in mountain ecosystems.Leaf carbon concentration(C),leaf nitrogen concentration(N),leaf phosphorous conce...Altitude affects leaf stoichiometry by regulating temperature and precipitation,and influencing soil properties in mountain ecosystems.Leaf carbon concentration(C),leaf nitrogen concentration(N),leaf phosphorous concentration(P),and their stoichiometric ratios of Leontopodium lentopodioides(Willd.)Beauv.,a widespread species in degraded grasslands,were investigated to explore its response and adaptation strategy to environmental changes along four altitude gradients(2500,3000,3500,and 3800 m a.s.l.)on the northeastern Qinghai-Tibetan Plateau(QTP),China.The leaf C significantly varied but without any clear trend with increasing altitude.Leaf N showed an increasing trend,and leaf P showed a little change with increasing altitude,with a lower value of leaf P at 3500 m than those at other altitudes.Similarity,leaf C:P and N:P exhibited a little change with increasing altitude,which both had greater values at 3500 m than those at other altitudes.However,leaf C:N exhibited a decreasing trend with increasing altitude.Soil NH^(+)_(4)-N,soil pH,soil total phosphorus(STP),mean annual temperature(MAT),and mean annual precipitation(MAP)were identified as the main factors driving the variations in leaf stoichiometry of L.lentopodioides across all altitudes,with NH^(+)_(4)-N alone accounting for 50.8%of its total variation.Specifically,leaf C and N were mainly controlled by MAT,soil pH,and NH^(+)_(4)-N,while leaf P by MAP and STP.In the study area,it seems that the growth of L.lentopodioides may be mainly limited by STP.The results could help to strengthen our understanding of the plasticity of plant growth to environmental changes and provide new information on global grassland management and restoration.展开更多
Plant macronutrient distribution in podzolized sands of the Amazon caatinga has received attention in several studies;however, the distribution of micronutrients has not been assessed. Soil micronutrient availability ...Plant macronutrient distribution in podzolized sands of the Amazon caatinga has received attention in several studies;however, the distribution of micronutrients has not been assessed. Soil micronutrient availability has been hypothesized to reflect contrasting habitat characteristics as well as fundamental differences in substrate, and leaf micronutrient composition may reflect the macronutrient content needed to maintain balance for leaf cell functions. In this study, soil and leaf samples were obtained in a toposequence (valley, slope, and mound). Available soil micro- and macronutrients as well as total leaf content were measured by inductively coupled plasma-atomic emission spectrometer and mass spectroscopy. Soil Zn (-1) and B (-1) as well as Cu (-1) levels were very low. Soil Mn was low in the valleys and slopes (0.62-0.87 mg·kg-1), but higher in the mound (6.59 mg·kg-1). Soil Fe (11.48-21.13 mg·kg-1) was well above the critical level in all of the habitats. Leaf micronutrients Cu, B, Zn, and Fe were below the critical levels for tropical crops of 3-7, 20-70, 15-20, and 72 mg·kg-1, respectively. Leaf Mn (88 mg·kg-1) and Al (<50 mg·kg-1) were below the accumulators level. A strong relationship between leaf micro- and macronutrients suggests the maintenance of a homeostatic elemental composition, which may favour photosynthetic function. Therefore, the local distribution of species may be shaped by their abilities to maintain a balance of micronutrient collected through roots under critically low levels of available Zn, B, and Cu whilst excluding potentially deleterious ions of Mn, Fe, and Al.展开更多
Particulate pollution is a serious health problem throughout the world, exacerbating a wide range of respiratory and vascular illnesses in urban areas. Urban plants play an important role in reducing particulate pollu...Particulate pollution is a serious health problem throughout the world, exacerbating a wide range of respiratory and vascular illnesses in urban areas. Urban plants play an important role in reducing particulate pollution. Physicochemical characteristics of ambient particles settling upon leaf surfaces of eleven roadside plants at four sites of Beijing were studies. Results showed that density of particles on the leaf surfaces greatly varied with plant species and traffic condition. Fraxinus chiuensis, Sophora japonica Ailanthus altissima, Syringa oblata and Prunus persica, had larger densities of particles among the tall species. Due to resuspension of road dust, the densities of particles of Euonymus japonicns and Parthenocissus quinquefolia with low sampling height were 2-35 times to other taller tree species. For test plant species, micro-roughness of leaf surfaces and density of particles showed a close correlation. In general, the larger micro-roughness of leaf surfaces is, the larger density of particles is. Particles settling upon leaf surfaces were dominantly PM30 （particulate matter less than 10 μm in aerodynamic diameter; 98.4%） and PM2.5 （particulate matter less than 2.5 μm in aerodynamic diameter; 64.2%） which were closely relative to human health. Constant elements of particles were C, O, K, Ca, Si, Al, Mg, Na, Fe, S, Cl and minerals with higher content were SiO2, CaCO3, CaMg（CO3）2, NaCI and 2CASO4. H2O, SiO2. CaCO3 and CaMg（CO3）2 mainly came from resuspension of road dust. 2CaSO4. H2O was produced by the reaction between CaCO3 derived from earth dust or industrial emission and SO2, H2SO4 or sulfate. NaCl was derived from sea salt.展开更多
Atomic absorption spectrophotometry,sulfuric acid and potassium dichromate oxidation method and ultraviolet spectrophotometry,were used to determine mineral elements,fiber,the content of chlorogenic acid and flavones ...Atomic absorption spectrophotometry,sulfuric acid and potassium dichromate oxidation method and ultraviolet spectrophotometry,were used to determine mineral elements,fiber,the content of chlorogenic acid and flavones in leaves of 24 Helianthus tuberosus Linn.resources,and the characteristics of the leaf introduced from abroad were evaluated.The results showed that the highest water content of 22 species was F12(27.58%),and the lowest was F16(19.02%).The difference in mean water content between the species from Denmark and France was small,but it was lower than that of Qingyu 3 and Qingyu 4.There were 3 orbicular leaves,1 long oval-shaped leaf and 18 oval leaves.The highest K content in the leaves was F19(30.62 mg/g),which was 2.5 times than Qingyu 3.The highest Mg content was D8(14.17 mg/g).The Fe content hadlittledifference,ranging from 0.09 mg/g to 0.19 mg/g.The highest Ca content was D8(26.87 mg/g).The highest level of chlorogenic acid and flavones was F7,2.55%and 1.24 g/100 g respectively.The highest fiber content was F9(16.7%),and the lowest was F19(7.36%).Through the analysis of the main component and the clustering analysis,when the genetic distance was 0.65,the 24 resources can be divided into three major categories.The first category of leaves were mainly oval and orbicular;the second category of leaves were long oval-shaped;the third category of leaves were oval.There was a difference between the various indexes in the leaf of different kinds of H.tuberosus Linn.resources.Finally,F19,D8,F9,F7,D14 and D11,6 specific species(F19,D8,F9,F7,D14 and D11)were screened out for further studies in the future.展开更多
Determination of nutrient contents in <i>Diospyros crassiflora</i> leaf litter was <span>carried out in the Forestry Research Institute of Nigeria (FRIN), Okwuta-Ibeku,</span> Umuahia, Abia Sta...Determination of nutrient contents in <i>Diospyros crassiflora</i> leaf litter was <span>carried out in the Forestry Research Institute of Nigeria (FRIN), Okwuta-Ibeku,</span> Umuahia, Abia State, Nigeria in 2016 and 2017. Three 1<span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 1</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m trays were randomly positioned for collection of leaf litter production from 4/5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">years old <i>Diospyros crassiflora</i> species in each block (10</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 25</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m) within the plantation totaling 1.5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">ha. A Randomised Complete Block Design (RCBD) with three replicates was used to study the mean monthly leaf litterfall of <i>Diospyros crassiflora</i>. Leaf litter was collected from each of the three litter trays per block and placed in paper bags every 28<sup>th</sup> day of each month from January-December in 2016 and in 2017. Fifteen grammes (15</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g) of properly mixed and oven-dried samples of <i>D. crassiflora</i> leaf litter were milled and sieved in 1</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">mm sieve;0.3</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g was used to determine nutrient elements and their concentrations. The data obtained from mineral nutrient contents of <i>D. crassiflora</i> leaf litter was analysed using analysis of variance. Result reveals the mean concentrations of nitrogen</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.41 and 1.41 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), phosphorus (0.18 and 0.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), potassium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.68 and 0.68 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), sodium (0.35 and 0.30 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), calcium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.57 and 1.56 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), magnesium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.32 and 0.31 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), chlorine (0.25 and 0.24 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), Organic carbon (0.03</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">and 0.03 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) and Organic matter</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.17 and 1.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) etc. in <i>D. crassiflora</i> leaf litter in January-December (2016 and 2017). The study shows almost uniform distribution of mineral elements concentrations in 2016 and 2017.</span></span></span>展开更多
A group of leaf springs which provides the flexible support of stator is designed to satisfy the requirement of low vibration motor at megawatt （MW） level. Spring steel 65Mn is chosen as the material of the leaf spr...A group of leaf springs which provides the flexible support of stator is designed to satisfy the requirement of low vibration motor at megawatt （MW） level. Spring steel 65Mn is chosen as the material of the leaf spring. The size of the leaf spring is obtained by calculation and load analysis according to a deflection formula. The deflection and stiffness of the single leaf spring is calculated with both theoretical method and finite element analysis （FEA）. A deflection test platform is established based on actual force and boundary condition to verify the deflection and stiffness of the leaf spring. The results show that the maximal deflection of the three pieces of 1.2 mm leaf spring group is 0.71 mm and the stiffness of the leaf spring group is 364 N/mm, which satisfies the requirements of the motor. The design method is also applicable for other MW power level motors.展开更多
In the process of milling the half-open impeller, the milling force ACTS on the half-open impeller will cause the machining deformation error of the half-open impeller. The impeller material studied in this paper is 7...In the process of milling the half-open impeller, the milling force ACTS on the half-open impeller will cause the machining deformation error of the half-open impeller. The impeller material studied in this paper is 7050-t7451 aluminum alloy, whose elastic modulus is 70.3 GPa, with low stiffness. Therefore, during milling, it is easy to cause elastic deformation of the cutter, thus causing machining errors and reducing machining surface quality. In addition, due to the low stiffness of blade surface, the deformation of blade surface is much larger than that of hub surface. Therefore, this paper only studies the deformation law of blade surface in the process of milling.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42030508)the Second Tibetan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0301)+3 种基金supported by CAS-TWAS President’s Fellowship Program for International Ph.D.studentssupported by Spanish Government(Grant Nos.PID2019-110521GB-I00 and TED2021-132627B-I00)the Catalan Government(Grant No.SGR 2017-1005)and the Fundación“Ramón Areces”(Grant No.CIVP20A6621)supported by the Spanish Government(Grant No.RTI2018-096884-B-C31)。
文摘Plants require a number of essential elements in different proportions for ensuring their growth and development.The elemental concentrations in leaves reflect the functions and adaptations of plants under specific environmental conditions.However,less is known about how the spectrum of leaf elements associated with resource acquisition,photosynthesis and growth regulates forest biomass along broad elevational gradients.We examined the influence of leaf element distribution and diversity on forest biomass by analyzing ten elements(C,N,P,K,Ca,Mg,Zn,Fe,Cu,and Mn)in tree communities situated every 100 meters along an extensive elevation gradient,ranging from the tropical forest(80 meters above sea level)to the alpine treeline(4200 meters above sea level)in the Kangchenjunga Landscape in eastern Nepal Himalayas.We calculated communityweighted averages(reflecting dominant traits governing biomass,i.e.,mass-ratio effect)and functional divergence(reflecting increased trait variety,i.e.,complementarity effect)for leaf elements in a total of 1,859 trees representing 116 species.An increasing mass-ratio effect and decreasing complementarity in leaf elements enhance forest biomass accumulation.A combination of elements together with elevation explains biomass(52.2%of the variance)better than individual elemental trait diversity(0.05%to 21%of the variance).Elevation modulates trait diversity among plant species in biomass accumulation.Complementarity promotes biomass at lower elevations,but reduces biomass at higher elevations,demonstrating an interaction between elevation and complementarity.The interaction between elevation and mass-ratio effect produces heterogeneous effects on biomass along the elevation gradient.Our research indicates that biomass accumulation can be disproportionately affected by elevation due to interactions among trait diversities across vegetation zones.While higher trait variation enhances the adaptation of species to environmental changes,it reduces biomass accumulation,especially at higher elevations.
基金National Natural Science Foundation of China(11362015)
文摘The problem of hydrodynamics of the three-leaf dislocated floating-ring bearing was studied by means of boundary element method.The law including the distribution of pressure on boundary surface(axial,bearing and floating-ring)and its friction loss in different eccentricities was obtained.The results show that the inner friction of three-leaf dislocated bearing increases from 390.875to 1 091.65,and the inner friction of three-leaf dislocated floating-ring bearing increases from 94.2523to 114.5069with eccentricity varying from 0to 0.075in nondimensional.So changing the pressure and flow field of bearing by adding floating-ring is more stability and less wasted work of friction than three-leaf dislocated bearing.
基金the Science and Technology Planning Project of Gansu Province,China(18JR4RA002)the Qilian Mountains Eco-Environment Research Center in Gansu Province,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences(QLS202002).
文摘Altitude affects leaf stoichiometry by regulating temperature and precipitation,and influencing soil properties in mountain ecosystems.Leaf carbon concentration(C),leaf nitrogen concentration(N),leaf phosphorous concentration(P),and their stoichiometric ratios of Leontopodium lentopodioides(Willd.)Beauv.,a widespread species in degraded grasslands,were investigated to explore its response and adaptation strategy to environmental changes along four altitude gradients(2500,3000,3500,and 3800 m a.s.l.)on the northeastern Qinghai-Tibetan Plateau(QTP),China.The leaf C significantly varied but without any clear trend with increasing altitude.Leaf N showed an increasing trend,and leaf P showed a little change with increasing altitude,with a lower value of leaf P at 3500 m than those at other altitudes.Similarity,leaf C:P and N:P exhibited a little change with increasing altitude,which both had greater values at 3500 m than those at other altitudes.However,leaf C:N exhibited a decreasing trend with increasing altitude.Soil NH^(+)_(4)-N,soil pH,soil total phosphorus(STP),mean annual temperature(MAT),and mean annual precipitation(MAP)were identified as the main factors driving the variations in leaf stoichiometry of L.lentopodioides across all altitudes,with NH^(+)_(4)-N alone accounting for 50.8%of its total variation.Specifically,leaf C and N were mainly controlled by MAT,soil pH,and NH^(+)_(4)-N,while leaf P by MAP and STP.In the study area,it seems that the growth of L.lentopodioides may be mainly limited by STP.The results could help to strengthen our understanding of the plasticity of plant growth to environmental changes and provide new information on global grassland management and restoration.
文摘Plant macronutrient distribution in podzolized sands of the Amazon caatinga has received attention in several studies;however, the distribution of micronutrients has not been assessed. Soil micronutrient availability has been hypothesized to reflect contrasting habitat characteristics as well as fundamental differences in substrate, and leaf micronutrient composition may reflect the macronutrient content needed to maintain balance for leaf cell functions. In this study, soil and leaf samples were obtained in a toposequence (valley, slope, and mound). Available soil micro- and macronutrients as well as total leaf content were measured by inductively coupled plasma-atomic emission spectrometer and mass spectroscopy. Soil Zn (-1) and B (-1) as well as Cu (-1) levels were very low. Soil Mn was low in the valleys and slopes (0.62-0.87 mg·kg-1), but higher in the mound (6.59 mg·kg-1). Soil Fe (11.48-21.13 mg·kg-1) was well above the critical level in all of the habitats. Leaf micronutrients Cu, B, Zn, and Fe were below the critical levels for tropical crops of 3-7, 20-70, 15-20, and 72 mg·kg-1, respectively. Leaf Mn (88 mg·kg-1) and Al (<50 mg·kg-1) were below the accumulators level. A strong relationship between leaf micro- and macronutrients suggests the maintenance of a homeostatic elemental composition, which may favour photosynthetic function. Therefore, the local distribution of species may be shaped by their abilities to maintain a balance of micronutrient collected through roots under critically low levels of available Zn, B, and Cu whilst excluding potentially deleterious ions of Mn, Fe, and Al.
基金The National Natural Science Foundation of China (No. 30570338) the Natural Science Foundation of Beijing (No. 6053026) andthe Ministry of Education, China(No. 20040027020).
文摘Particulate pollution is a serious health problem throughout the world, exacerbating a wide range of respiratory and vascular illnesses in urban areas. Urban plants play an important role in reducing particulate pollution. Physicochemical characteristics of ambient particles settling upon leaf surfaces of eleven roadside plants at four sites of Beijing were studies. Results showed that density of particles on the leaf surfaces greatly varied with plant species and traffic condition. Fraxinus chiuensis, Sophora japonica Ailanthus altissima, Syringa oblata and Prunus persica, had larger densities of particles among the tall species. Due to resuspension of road dust, the densities of particles of Euonymus japonicns and Parthenocissus quinquefolia with low sampling height were 2-35 times to other taller tree species. For test plant species, micro-roughness of leaf surfaces and density of particles showed a close correlation. In general, the larger micro-roughness of leaf surfaces is, the larger density of particles is. Particles settling upon leaf surfaces were dominantly PM30 （particulate matter less than 10 μm in aerodynamic diameter; 98.4%） and PM2.5 （particulate matter less than 2.5 μm in aerodynamic diameter; 64.2%） which were closely relative to human health. Constant elements of particles were C, O, K, Ca, Si, Al, Mg, Na, Fe, S, Cl and minerals with higher content were SiO2, CaCO3, CaMg（CO3）2, NaCI and 2CASO4. H2O, SiO2. CaCO3 and CaMg（CO3）2 mainly came from resuspension of road dust. 2CaSO4. H2O was produced by the reaction between CaCO3 derived from earth dust or industrial emission and SO2, H2SO4 or sulfate. NaCl was derived from sea salt.
文摘Atomic absorption spectrophotometry,sulfuric acid and potassium dichromate oxidation method and ultraviolet spectrophotometry,were used to determine mineral elements,fiber,the content of chlorogenic acid and flavones in leaves of 24 Helianthus tuberosus Linn.resources,and the characteristics of the leaf introduced from abroad were evaluated.The results showed that the highest water content of 22 species was F12(27.58%),and the lowest was F16(19.02%).The difference in mean water content between the species from Denmark and France was small,but it was lower than that of Qingyu 3 and Qingyu 4.There were 3 orbicular leaves,1 long oval-shaped leaf and 18 oval leaves.The highest K content in the leaves was F19(30.62 mg/g),which was 2.5 times than Qingyu 3.The highest Mg content was D8(14.17 mg/g).The Fe content hadlittledifference,ranging from 0.09 mg/g to 0.19 mg/g.The highest Ca content was D8(26.87 mg/g).The highest level of chlorogenic acid and flavones was F7,2.55%and 1.24 g/100 g respectively.The highest fiber content was F9(16.7%),and the lowest was F19(7.36%).Through the analysis of the main component and the clustering analysis,when the genetic distance was 0.65,the 24 resources can be divided into three major categories.The first category of leaves were mainly oval and orbicular;the second category of leaves were long oval-shaped;the third category of leaves were oval.There was a difference between the various indexes in the leaf of different kinds of H.tuberosus Linn.resources.Finally,F19,D8,F9,F7,D14 and D11,6 specific species(F19,D8,F9,F7,D14 and D11)were screened out for further studies in the future.
文摘Determination of nutrient contents in <i>Diospyros crassiflora</i> leaf litter was <span>carried out in the Forestry Research Institute of Nigeria (FRIN), Okwuta-Ibeku,</span> Umuahia, Abia State, Nigeria in 2016 and 2017. Three 1<span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 1</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m trays were randomly positioned for collection of leaf litter production from 4/5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">years old <i>Diospyros crassiflora</i> species in each block (10</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 25</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m) within the plantation totaling 1.5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">ha. A Randomised Complete Block Design (RCBD) with three replicates was used to study the mean monthly leaf litterfall of <i>Diospyros crassiflora</i>. Leaf litter was collected from each of the three litter trays per block and placed in paper bags every 28<sup>th</sup> day of each month from January-December in 2016 and in 2017. Fifteen grammes (15</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g) of properly mixed and oven-dried samples of <i>D. crassiflora</i> leaf litter were milled and sieved in 1</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">mm sieve;0.3</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g was used to determine nutrient elements and their concentrations. The data obtained from mineral nutrient contents of <i>D. crassiflora</i> leaf litter was analysed using analysis of variance. Result reveals the mean concentrations of nitrogen</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.41 and 1.41 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), phosphorus (0.18 and 0.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), potassium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.68 and 0.68 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), sodium (0.35 and 0.30 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), calcium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.57 and 1.56 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), magnesium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.32 and 0.31 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), chlorine (0.25 and 0.24 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), Organic carbon (0.03</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">and 0.03 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) and Organic matter</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.17 and 1.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) etc. in <i>D. crassiflora</i> leaf litter in January-December (2016 and 2017). The study shows almost uniform distribution of mineral elements concentrations in 2016 and 2017.</span></span></span>
基金Supported by the Development and Application Research of Marine Electric Propulsion System of the Ministry of Science and Technology(2012BAG03B01)the National Natural Science Foundation of China(51205292)
文摘A group of leaf springs which provides the flexible support of stator is designed to satisfy the requirement of low vibration motor at megawatt （MW） level. Spring steel 65Mn is chosen as the material of the leaf spring. The size of the leaf spring is obtained by calculation and load analysis according to a deflection formula. The deflection and stiffness of the single leaf spring is calculated with both theoretical method and finite element analysis （FEA）. A deflection test platform is established based on actual force and boundary condition to verify the deflection and stiffness of the leaf spring. The results show that the maximal deflection of the three pieces of 1.2 mm leaf spring group is 0.71 mm and the stiffness of the leaf spring group is 364 N/mm, which satisfies the requirements of the motor. The design method is also applicable for other MW power level motors.
文摘In the process of milling the half-open impeller, the milling force ACTS on the half-open impeller will cause the machining deformation error of the half-open impeller. The impeller material studied in this paper is 7050-t7451 aluminum alloy, whose elastic modulus is 70.3 GPa, with low stiffness. Therefore, during milling, it is easy to cause elastic deformation of the cutter, thus causing machining errors and reducing machining surface quality. In addition, due to the low stiffness of blade surface, the deformation of blade surface is much larger than that of hub surface. Therefore, this paper only studies the deformation law of blade surface in the process of milling.
