The particle residence time distribution(RTD)and axial dispersion coefficient are key parameters for the design and operation of a pressurized circulating fluidized bed(PCFB).In this study,the effects of pressure(0.1-...The particle residence time distribution(RTD)and axial dispersion coefficient are key parameters for the design and operation of a pressurized circulating fluidized bed(PCFB).In this study,the effects of pressure(0.1-0.6 MPa),fluidizing gas velocity(2-7 m·s^(-1)),and solid circulation rate(10-90 kg·m^(-2)·s^(-1))on particle RTD and axial dispersion coefficient in a PCFB are numerically investigated based on the multiphase particle-in-cell(MP-PIC)method.The details of the gas-solid flow behaviors of PCFB are revealed.Based on the gas-solid flow pattern,the particles tend to move more orderly under elevated pressures.With an increase in either fluidizing gas velocity or solid circulation rate,the mean residence time of particles decreases while the axial dispersion coefficient increases.With an increase in pressure,the core-annulus flow is strengthened,which leads to a wider shape of the particle RTD curve and a larger mean particle residence time.The back-mixing of particles increases with increasing pressure,resulting in an increase in the axial dispersion coefficient.展开更多
Vertical structures of momentum exchange coefficient and sediment concentration are the keys in the research on es- tuarine and coastal suspended sediment transport. Based on the parabolic mixing length distribution p...Vertical structures of momentum exchange coefficient and sediment concentration are the keys in the research on es- tuarine and coastal suspended sediment transport. Based on the parabolic mixing length distribution pattern, the distribu- tion pattern of vertical momentum exchange coefficient which is suitable for estuarine and coastal waters is constructed. A compari^n with steady flow and measured momentum exchange coefficient during one tidal cycle in the Menai Strait of England shows that the result of this pattern is closer to the measured values than those of commonly used Rouse' s and van Rijn's patterns, and the pattern is also suitable for estuarine and coastal waters. Successively, based on the precon- dition that momentum exchange coefficient is equivalent to sediment turbulent diffusion coefficient, and combining with the Diffusion Theory, we obtain the exponential vertical distribution pattern of sediment concentration, which is also suitable for estuafine and coastal waters, Thereby, using measured vertical stratified sediment concentration data of the South and the North Passages of the Yangtze Estuary and Zhoushan archipelago waters for fitting calculation, and comparing the results with those from Rouse's (1938) and Zhang et al. 's (1989) formulas, the results show that the exponential vertical distribution pattern of sediment concentration obtained in the present study not only overcomes the defect of Rouse's formula that the surface sediment concentration will be 0, but also has a holistic higher precision along the vertical lines than those of Rouse's and Zhang et al. 's formulas.展开更多
Troxerutin fatty acid esters were prepared using troxerutin and fatty acid vinyl esters as substrates in pyridine through enzymatic route. The structures of as-prepared compounds were identified by FT-TR, NMR, and ESI...Troxerutin fatty acid esters were prepared using troxerutin and fatty acid vinyl esters as substrates in pyridine through enzymatic route. The structures of as-prepared compounds were identified by FT-TR, NMR, and ESI-HRMS. Using alkaline protease(≥30 mg/mL) as enzyme, maximum yields reached 58% at 3:1(vinyl hexanoate to troxerutin) in pyridine(water content ≤1%). The yields gradually declined as chain length of acyl donors rose. The antioxidation abilities of the as-obtained compounds were confirmed by both DPPH free radical scavenging and potassium ferricyanide reduction methods. The antioxidation ability of troxerutin fatty acid esters was found lower than that of troxerutin. However, the logP values of troxerutin fatty acid esters varied from 0.15 to 1.94, suggesting that troxerutin fatty acid esters had better lipophilicity than troxerutin(logP =-2.12) when compared to their oil-water distribution coefficients. Overall, these findings look promising as reference for further development of future troxerutin.展开更多
This paper presents a method to acquire runtime distribution ratio of building air conditioning system under part load condition (part load coefficient of system) through practical energy consumption data. By utilizin...This paper presents a method to acquire runtime distribution ratio of building air conditioning system under part load condition (part load coefficient of system) through practical energy consumption data. By utilizing monthly energy consumption data of the entire year as the analysis object,this paper identifies data distribution,verifies distribution characteristics and analyzes distribution probability density for the issue of running time distribution ratio of air conditioning system in part load zones in the whole operation period,thus providing a basic calculation basis for an overall analysis of energy efficiency of air conditioning system. In view of the general survey of public building energy consumption carried by the government of Chongqing,this paper takes the governmental office building as an example,the part load ratio coefficient corresponding to practical running of air conditioning system of governmental office building in Chongqing is obtained by utilizing the above probability analysis and the solving method of probability density function. By utilizing the ratio coefficient obtained using this method,the part load coefficient with any running ratio of air conditioning system can be obtained according to the requirement of analysis,which can be used in any load ratio for analyzing running energy efficiency of air conditioning system.展开更多
A computational approach is presented to handle an enlarged linear rotordynamic model whichsimultaneously includes both radial and misalignment motions.The interactive force and momentbetween the rotating and non-rota...A computational approach is presented to handle an enlarged linear rotordynamic model whichsimultaneously includes both radial and misalignment motions.The interactive force and momentbetween the rotating and non-rotating members are modeled using an adaptation of the classicalReynolds lubrication equation for incompressible laminar isoviscous films.First,the governingequation is derived and the method of solution is introduced based on a 2-dimension,9-point cen-tral difference.Second,force and moment components are computed by numerical integration ofthe film pressure distribution.Finally,the rotordynamic coefficients are yielded according to thegeneralized force gradients.展开更多
A wind tunnel tests with different configurations,pitch and yaw angles were performed to study the wind load characteristics of the rigid model of the airship Zhiyuan-1. The rigid model was aimed to simulate a technic...A wind tunnel tests with different configurations,pitch and yaw angles were performed to study the wind load characteristics of the rigid model of the airship Zhiyuan-1. The rigid model was aimed to simulate a technical demonstrating stratospheric airship named Zhiyuan-1 according to the similarity principle of geometric and Reynolds number. Based on the results of wind tunnel test,the features of pressure coefficient distributions on the surface of the airship were described. It was indicated that the fins and the gondola of airship hardly have the effect on the pressure distribution on the surface of airship,but have obviously effect on the local areas near the fins and the gondola.展开更多
The distribution coefficient of return current network is an important method to decrease the rail potential. In order to resolve the problem of high rail potential in high-speed railway based on EN50122-1 and Pr EN50...The distribution coefficient of return current network is an important method to decrease the rail potential. In order to resolve the problem of high rail potential in high-speed railway based on EN50122-1 and Pr EN50170 the distribution coefficient of longitudinal traction return current conductors is calculated through changing the interval of transverse connection. Based on field data and theoretical analysis, the parameters of longitudinal traction return current conductors are calculated. Results indicate that the best distance of the transverse connection is 400 m – 600 m.展开更多
Measurements of bubble size distribution require the understanding of the acoustic characteristics of the medium.The bubbles show highly nonlinear properties under finite amplitude acoustic excitation,so the acoustic ...Measurements of bubble size distribution require the understanding of the acoustic characteristics of the medium.The bubbles show highly nonlinear properties under finite amplitude acoustic excitation,so the acoustic fields from bubble population are easily observed at the second harmonics as well as at the fundamental frequency,which shows that the nonlinear coefficient increases obviously.The inversion method of bubble size distribution based on nonlinear acoustic effects can peel off the influence of complex environment and obtain the size distribution coefficient information of bubbles more accurately.The previous nonlinear inversion methods of bubble size distribution are mostly based on the nonlinear scattering cross-section characteristics of bubbles.However,the stability of inversion is not high enough.In this paper,we introduce a new acoustic inversion method for bubble size distribution,which is based on the nonlinear coefficients of bubble medium.Compared with other inversion methods based on linear or nonlinear scattering cross section,the inversion method based on nonlinear coefficients of bubble medium proposed in this paper shows good robustness in both simulation and experiment.展开更多
The exact classical limits for the coefficient of variation c for the normal distribution are derived. The hand-calculating approximated classical limits for c having high accuracy are given to meet practical engineer...The exact classical limits for the coefficient of variation c for the normal distribution are derived. The hand-calculating approximated classical limits for c having high accuracy are given to meet practical engineering needs. Using Odeh and Owen's computational method and Brent's algorithm, the tables for the r-upper exact classical limits of coefficient of variation for normal distribution are calculated for the different confidence coefficient y, the sample size n=1(1)30,40,60,120, the sample coefficient of variation c=0.01(0.01)0.20. It is shown that if n<8,c<0.20, then the V -upper exact classical limits cu for c are slightly higher than the exact fiducial limits cu,F for c if. n>8, c<0.02,then cu-cu,f<5x10-6展开更多
When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interface energy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation betw...When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interface energy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation between the distribution of solute at solid-liquid interface and current density was established, and the effect of current on the distribution coefficient of solute through effecting the rate of crystal growth, the solid-liquid interface energy and the radius of curvature at the dendritic tip was discussed. The results show that as the current density increases, the distribution coefficient of solute tends to rise in a whole, and when the former is larger than about 400 A/cm 2, the latter varies significantly.展开更多
In this paper, primary manufacturing and assembling errors of three-ring gear reducer (TRGR) are analyzed. TRGR is a new transmission type whose eccentric phase difference between middle ring plate and side ring plate...In this paper, primary manufacturing and assembling errors of three-ring gear reducer (TRGR) are analyzed. TRGR is a new transmission type whose eccentric phase difference between middle ring plate and side ring plates is 120°. Its mass of middle ring plate is equal to that of side ring plate or 180°, and its mass of middle ring plate is twice of that of side ring plate, which affects load distribution between ring plates. The primary manufacturing and assembling errors include eccentric error of eccentric sheath E_m, internal gear plate E_r and output external gear E_w. A new theoretical method is presented in this paper, which converts load on ring plates into the dedendum bending stress of ring plate to calculate load distribution coefficient (LDC), by means of gap element method(GEM), one of finite element method (FEM). The theoretical calculation and experimental study, which measures ring plate dedendum bending stress by means of sticking strain gauges on the dedendum of middle ring plate internal gear and side ring plate internal gears, are presented. The theoretical calculation and comparison with experiment result of LDC are implemented on two kinds of three-ring gear reducers whose eccentric phase difference between eccentric sheaths is 120° and 180° respectively. The research indicates that the result of theoretical calculation is consistent with that of experimental study. That is to say, the theoretical calculation method is feasible.展开更多
The distributed Lagrange multiplier/fictitious domain(DLM/FD)-mixed finite element method is developed and analyzed in this paper for a transient Stokes interface problem with jump coefficients.The semi-and fully disc...The distributed Lagrange multiplier/fictitious domain(DLM/FD)-mixed finite element method is developed and analyzed in this paper for a transient Stokes interface problem with jump coefficients.The semi-and fully discrete DLM/FD-mixed finite element scheme are developed for the first time for this problem with a moving interface,where the arbitrary Lagrangian-Eulerian(ALE)technique is employed to deal with the moving and immersed subdomain.Stability and optimal convergence properties are obtained for both schemes.Numerical experiments are carried out for different scenarios of jump coefficients,and all theoretical results are validated.展开更多
While the spatial distribution pattern of fish is increasingly used for toxicological test o chemicals or wastewater,no ideal parameter is available for quantitative assessment of spa tial distribution,especially unev...While the spatial distribution pattern of fish is increasingly used for toxicological test o chemicals or wastewater,no ideal parameter is available for quantitative assessment of spa tial distribution,especially uneven distribution with multiple hotspots.Here,to develop a quantitative assessment parameter for spatial distribution,the zebrafish were exposed to ethanol,pentylenetetrazole(PTZ),paraquat dichloride(paraquat)and wastewater,followed by a behavioral test in a narrow tank.Behavioral data was acquired and analyzed by id Tracker and MATLAB.By comparing the effects of all treatments on behavior parameters we confirmed that the spatial distribution was more easily altered rather than general loco motor parameters,e.g.0.7-70 mg/L PTZ and 5-20 mg/L paraquat being effective for altering spatial distribution but having little effects on general locomotor parameters.Based on the heatmap,i.e.,the cumulative proportion of grids and that of frequency in grids,we calcu lated the behavioral Gini coefficient(G_(b))for quantitative assessment of fish spatial distri bution.The Gini coefficient ranged from zero to 1,with larger values meaning poorer even ness of spatial distribution.Of note,G_(b)showed smaller coefficient of variations(CV)with3%-19%between replicate tanks in all treatments than the highest frequency(4%-79%),dis playing well robustness.Especially,G_(b)addressed the challenge of the complicated heatmap with multiple hotspots.Overall,the behavioral Gini coefficient we established is an idea parameter to quantitatively assess spatial distribution of fish shoal,which is expected to be applied in toxicity testing for chemicals and wastewater and automatic quality monitoring for surface water and aquaculture water.展开更多
Polycyclic aromatic hydrocarbons (PAHs) were measured in precipitation from March to August 2005 in Guangzhou, South China. Fourteen PAHs were studied, and their total concentrations varied from 616.6 to 3486.7 ng/L...Polycyclic aromatic hydrocarbons (PAHs) were measured in precipitation from March to August 2005 in Guangzhou, South China. Fourteen PAHs were studied, and their total concentrations varied from 616.6 to 3486.7 ng/L in dissolved phase and from 403.8 to 3125.5 ng/L in particulate phase. The estimated deposition loading of PAHs was 3568 ug/m^2 during the monitoring period. The deposition of PAHs was a potential source for Pearl River comparing with the contents of surface water. In addition, the high concentration in precipitation here implied that PAHs pollution was a potential environmental problem in Guangzhou. Most precipitation concentrations of PAHs in March (the last month in winter in Guangzhou) were higher than in the other months (in rainy season). PAHs inclined to be adsorbed to particulate phase with the increase of molecular weight in rainwater. Combustion of fossil fuel and biomass might be the major source of PAHs, while the direct leakage or volatilization from petroleum products might be insignificant.展开更多
Climate change will have important implications in water shore regions,such as Huang-Huai-Hai(3H) plain,where expected warmer and drier conditions might augment crop water demand.Sensitivity analysis is important in...Climate change will have important implications in water shore regions,such as Huang-Huai-Hai(3H) plain,where expected warmer and drier conditions might augment crop water demand.Sensitivity analysis is important in understanding the relative importance of climatic variables to the variation in reference evapotranspiration(ET 0).In this study,the 51-yr ET 0 during winter wheat and summer maize growing season were calculated from a data set of daily climate variables in 40 meteorological stations.Sensitivity maps for key climate variables were estimated according to Kriging method and the spatial pattern of sensitivity coefficients for these key variables was plotted.In addition,the slopes of the linear regression lines for sensitivity coefficients were obtained.Results showed that ET 0 during winter wheat growing season accounted for the largest proportion of annual ET 0,due to its long phenological days,while ET 0 was detected to decrease significantly with the magnitude of 0.5 mm yr-1in summer maize growing season.Solar radiation is considered to be the most sensitive and primarily controlling variable for negative trend in ET 0 for summer maize season,and higher sensitive coefficient value of ET 0 to solar radiation and temperature were detected in east part and southwest part of 3H plain respectively.Relative humidity was demonstrated as the most sensitive factor for ET 0 in winter wheat growing season and declining relativity humidity also primarily controlled a negative trend in ET 0,furthermore the sensitivity coefficient to relative humidity increased from west to southeast.The eight sensitivity centrals were all found located in Shandong Province.These ET 0 along with its sensitivity maps under winter wheat-summer maize rotation system can be applied to predict the agricultural water demand and will assist water resources planning and management for this region.展开更多
Grain composition plays a vital role in impact pressure of debris flow. Current approaches treat debris flow as uniform fluid and almost ignore its granular effects. A series of flume experiments have been carried out...Grain composition plays a vital role in impact pressure of debris flow. Current approaches treat debris flow as uniform fluid and almost ignore its granular effects. A series of flume experiments have been carried out to explore the granular influence on the impact process of debris flow by using a contact surface pressure gauge sensor(Tactilus~?, produced by Sensor Products LLC). It is found that the maximum impact pressure for debris flow of low density fluctuates drastically with a long duration time while the fluctuation for flow of high density is short in time, respectively presenting logarithmic and linear form in longitudinal attenuation. This can be ascribed to the turbulence effect in the former and grain collisions and grainfluid interaction in the latter. The horizontal distribution of the impact pressure can be considered as the equivalent distribution. For engineering purposes, the longitudinal distribution of the pressure can be generalized to a triangular distribution, from which a new impact method considering granular effects is proposed.展开更多
Black locust(Robinia pseudoacacia L.) and Chinese pine(Pinus tabulaeformis Carr.) are two woody plants that are widely planted on the Loess Plateau for controlling soil erosion and land desertification. In this st...Black locust(Robinia pseudoacacia L.) and Chinese pine(Pinus tabulaeformis Carr.) are two woody plants that are widely planted on the Loess Plateau for controlling soil erosion and land desertification. In this study, we conducted an excavation experiment in 2008 to investigate the overall vertical root distribution characteristics of black locust and Chinese pine. We also performed triaxial compression tests to evaluate the root cohesion(additional soil cohesion increased by roots) of black locust. Two types of root distribution, namely, vertical root(VR) and horizontal root(HR), were used as samples and tested under four soil water content(SWC) conditions(12.7%, 15.0%, 18.0% and 20.0%, respectively). Results showed that the root lengths of the two species were mainly concentrated in the root diameter of 5–20 mm. A comparison of root distribution between the two species indicated that the root length of black locust was significantly greater than that of Chinese pine in nearly all root diameters, although the black locust used in the comparison was 10 years younger than the Chinese pine. Root biomass was also significantly greater in black locust than in Chinese pine, particularly in the root diameters of 3–5 and 5–10 mm. These two species were both found to be deep-rooted. The triaxial compression tests showed that root cohesion was greater in the VR samples than in the HR samples. SWC was negatively related to both soil shear strength and root cohesion. These results could provide useful information on the architectural characteristics of woody root system and expand the knowledge on shallow slope stabilization and soil erosion control by plant roots on the Loess Plateau.展开更多
Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone (ATE) of Taihu Lake were investigated, and the relations among N, P, ORP (oxidation reduction potential), TOC, root sy...Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone (ATE) of Taihu Lake were investigated, and the relations among N, P, ORP (oxidation reduction potential), TOC, root system biomass and microorganism were studied. As a whole, significant declines in TN, NO3^--N, DON (dissolved organic nitrogen) and TP concentration in soil solution have occurred with increase of the depth, and reached their minima at 60 cm depth, except for NH4^+-N, which increased with depth. The concentration of TP increased gradually from spring to winter in the topsoil, the maximum 0.08 mg/L presented in the winter while the minimum 0.03 mg/L in spring. In the deeper layer, the concentration value of TP fluctuated little. As for the NO3^--N, its seasonal variation was significant at 20 cm depth, its concentration increased gradually from spring to autumn, and decreased markedly in winter. Vertical and temporal distribution of DON is contrary to that of NO3^--N. The results also show that the variation of N and P in the percolate between adjacent layers is obviously different. The vertical variation ofTN, TP, NO3^--N, NH4^+-N and DON is significant, of which the variation coefficient of NO3^--N along the depth reaches 100.23%, the highest; while the variation coefficient of DON is 41.14%, the smallest. The results of correlation analysis show that the concentration of nitrogen and phosphorus correlate significantly with TOC, ORP, root biomass and counts of nitrifying bacteria. Most nutrients altered much from 20 to 40 cm along the depth. However, DON changed more between 60 and 80 cm. Results show that soil of 0-60 cm depth is active rhizoplane, with strong capability to remove the nitrogen and phosphorus in ATE. It may suggest that there exists the optimum ecological efficiency in the depth of above 60 cm in reed wetland. This will be very significant for ecological restoration and reestablishment.展开更多
Objective Allocation of human resources to address inequalities in the public health system has increasingly attracted societal and political attention.Using the Centers for Disease Control and Prevention(CDCs)system ...Objective Allocation of human resources to address inequalities in the public health system has increasingly attracted societal and political attention.Using the Centers for Disease Control and Prevention(CDCs)system of China as an example,we evaluated inequality in the public health workforce distribution across different regions in China between 2008 and 2017,with the aim of providing information for policymakers to support resource allocation and address growing health inequities.Methods We used three standard public health workforce inequality indices-Gini coefficient,Theil L,and Theil T-and spatial autocorrelation analysis to explore spatial clusters of the workforce in different provinces,visualized with geographical tools.Results The aggregate workforce-to-population ratio decreased from 1.47 to 1.42 per 10,000 population from 2008 to 2017,and was consistently lower than the National Health Commission’s(NHC)recommended critical shortage threshold of 1.75.The workforce distribution inequality indices varied by regional socioeconomic and health system development.Geographic clustering of CDCs workforce distribution was evident,with H–H and L–L clusters in western China and the Guangdong-Fujian region,respectively.Conclusions Our study addressed key issues for government and policymakers in allocation of public health human resources.There is an urgent need for careful identification of analytic questions that will help carry out public health functions in the new era,alongside policy implications for an equitable distribution of the public health workforce focusing on the western region and low–low cluster areas.展开更多
基金Financial support of this work by National Natural Science Foundation of China(51976037)。
文摘The particle residence time distribution(RTD)and axial dispersion coefficient are key parameters for the design and operation of a pressurized circulating fluidized bed(PCFB).In this study,the effects of pressure(0.1-0.6 MPa),fluidizing gas velocity(2-7 m·s^(-1)),and solid circulation rate(10-90 kg·m^(-2)·s^(-1))on particle RTD and axial dispersion coefficient in a PCFB are numerically investigated based on the multiphase particle-in-cell(MP-PIC)method.The details of the gas-solid flow behaviors of PCFB are revealed.Based on the gas-solid flow pattern,the particles tend to move more orderly under elevated pressures.With an increase in either fluidizing gas velocity or solid circulation rate,the mean residence time of particles decreases while the axial dispersion coefficient increases.With an increase in pressure,the core-annulus flow is strengthened,which leads to a wider shape of the particle RTD curve and a larger mean particle residence time.The back-mixing of particles increases with increasing pressure,resulting in an increase in the axial dispersion coefficient.
基金supported by the National Key Basic Research Development Programof China (973 Program, Grant No.2010CB429002)the Foundation of the Key Laboratory of Port, Waterway and Sedimentation Engineering, Min-istry of Communications, PRC (Subject : The Vertical Characteristics of suspended sediment transport in Estuary)the Natural Science Foundation of Jiangsu Province (Grant No.BK2007179)
文摘Vertical structures of momentum exchange coefficient and sediment concentration are the keys in the research on es- tuarine and coastal suspended sediment transport. Based on the parabolic mixing length distribution pattern, the distribu- tion pattern of vertical momentum exchange coefficient which is suitable for estuarine and coastal waters is constructed. A compari^n with steady flow and measured momentum exchange coefficient during one tidal cycle in the Menai Strait of England shows that the result of this pattern is closer to the measured values than those of commonly used Rouse' s and van Rijn's patterns, and the pattern is also suitable for estuarine and coastal waters. Successively, based on the precon- dition that momentum exchange coefficient is equivalent to sediment turbulent diffusion coefficient, and combining with the Diffusion Theory, we obtain the exponential vertical distribution pattern of sediment concentration, which is also suitable for estuafine and coastal waters, Thereby, using measured vertical stratified sediment concentration data of the South and the North Passages of the Yangtze Estuary and Zhoushan archipelago waters for fitting calculation, and comparing the results with those from Rouse's (1938) and Zhang et al. 's (1989) formulas, the results show that the exponential vertical distribution pattern of sediment concentration obtained in the present study not only overcomes the defect of Rouse's formula that the surface sediment concentration will be 0, but also has a holistic higher precision along the vertical lines than those of Rouse's and Zhang et al. 's formulas.
基金financially supported by Science and Technology Department of Henan Province (No. 132102310028)the Program for Innovative Research Team from Zhengzhou (No. 131PCXTD605)
文摘Troxerutin fatty acid esters were prepared using troxerutin and fatty acid vinyl esters as substrates in pyridine through enzymatic route. The structures of as-prepared compounds were identified by FT-TR, NMR, and ESI-HRMS. Using alkaline protease(≥30 mg/mL) as enzyme, maximum yields reached 58% at 3:1(vinyl hexanoate to troxerutin) in pyridine(water content ≤1%). The yields gradually declined as chain length of acyl donors rose. The antioxidation abilities of the as-obtained compounds were confirmed by both DPPH free radical scavenging and potassium ferricyanide reduction methods. The antioxidation ability of troxerutin fatty acid esters was found lower than that of troxerutin. However, the logP values of troxerutin fatty acid esters varied from 0.15 to 1.94, suggesting that troxerutin fatty acid esters had better lipophilicity than troxerutin(logP =-2.12) when compared to their oil-water distribution coefficients. Overall, these findings look promising as reference for further development of future troxerutin.
基金Project(50838009) supported by the National Natural Science Foundation of ChinaProjects(2006BAJ02A09,2006BAJ02A13-4) supported by the National Key Technologies R & D Program of ChinaProject(CSTC,2008AB7110) supported by the Key Technologies R & D Programme of Chongqing,China
文摘This paper presents a method to acquire runtime distribution ratio of building air conditioning system under part load condition (part load coefficient of system) through practical energy consumption data. By utilizing monthly energy consumption data of the entire year as the analysis object,this paper identifies data distribution,verifies distribution characteristics and analyzes distribution probability density for the issue of running time distribution ratio of air conditioning system in part load zones in the whole operation period,thus providing a basic calculation basis for an overall analysis of energy efficiency of air conditioning system. In view of the general survey of public building energy consumption carried by the government of Chongqing,this paper takes the governmental office building as an example,the part load ratio coefficient corresponding to practical running of air conditioning system of governmental office building in Chongqing is obtained by utilizing the above probability analysis and the solving method of probability density function. By utilizing the ratio coefficient obtained using this method,the part load coefficient with any running ratio of air conditioning system can be obtained according to the requirement of analysis,which can be used in any load ratio for analyzing running energy efficiency of air conditioning system.
文摘A computational approach is presented to handle an enlarged linear rotordynamic model whichsimultaneously includes both radial and misalignment motions.The interactive force and momentbetween the rotating and non-rotating members are modeled using an adaptation of the classicalReynolds lubrication equation for incompressible laminar isoviscous films.First,the governingequation is derived and the method of solution is introduced based on a 2-dimension,9-point cen-tral difference.Second,force and moment components are computed by numerical integration ofthe film pressure distribution.Finally,the rotordynamic coefficients are yielded according to thegeneralized force gradients.
文摘A wind tunnel tests with different configurations,pitch and yaw angles were performed to study the wind load characteristics of the rigid model of the airship Zhiyuan-1. The rigid model was aimed to simulate a technical demonstrating stratospheric airship named Zhiyuan-1 according to the similarity principle of geometric and Reynolds number. Based on the results of wind tunnel test,the features of pressure coefficient distributions on the surface of the airship were described. It was indicated that the fins and the gondola of airship hardly have the effect on the pressure distribution on the surface of airship,but have obviously effect on the local areas near the fins and the gondola.
文摘The distribution coefficient of return current network is an important method to decrease the rail potential. In order to resolve the problem of high rail potential in high-speed railway based on EN50122-1 and Pr EN50170 the distribution coefficient of longitudinal traction return current conductors is calculated through changing the interval of transverse connection. Based on field data and theoretical analysis, the parameters of longitudinal traction return current conductors are calculated. Results indicate that the best distance of the transverse connection is 400 m – 600 m.
基金the National Natural Science Foundation of China(Grant Nos.11674074 and 61701133).
文摘Measurements of bubble size distribution require the understanding of the acoustic characteristics of the medium.The bubbles show highly nonlinear properties under finite amplitude acoustic excitation,so the acoustic fields from bubble population are easily observed at the second harmonics as well as at the fundamental frequency,which shows that the nonlinear coefficient increases obviously.The inversion method of bubble size distribution based on nonlinear acoustic effects can peel off the influence of complex environment and obtain the size distribution coefficient information of bubbles more accurately.The previous nonlinear inversion methods of bubble size distribution are mostly based on the nonlinear scattering cross-section characteristics of bubbles.However,the stability of inversion is not high enough.In this paper,we introduce a new acoustic inversion method for bubble size distribution,which is based on the nonlinear coefficients of bubble medium.Compared with other inversion methods based on linear or nonlinear scattering cross section,the inversion method based on nonlinear coefficients of bubble medium proposed in this paper shows good robustness in both simulation and experiment.
文摘The exact classical limits for the coefficient of variation c for the normal distribution are derived. The hand-calculating approximated classical limits for c having high accuracy are given to meet practical engineering needs. Using Odeh and Owen's computational method and Brent's algorithm, the tables for the r-upper exact classical limits of coefficient of variation for normal distribution are calculated for the different confidence coefficient y, the sample size n=1(1)30,40,60,120, the sample coefficient of variation c=0.01(0.01)0.20. It is shown that if n<8,c<0.20, then the V -upper exact classical limits cu for c are slightly higher than the exact fiducial limits cu,F for c if. n>8, c<0.02,then cu-cu,f<5x10-6
文摘When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interface energy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation between the distribution of solute at solid-liquid interface and current density was established, and the effect of current on the distribution coefficient of solute through effecting the rate of crystal growth, the solid-liquid interface energy and the radius of curvature at the dendritic tip was discussed. The results show that as the current density increases, the distribution coefficient of solute tends to rise in a whole, and when the former is larger than about 400 A/cm 2, the latter varies significantly.
基金Sponsored by the National Natural Science Foundation of China(Grant No.59575007).
文摘In this paper, primary manufacturing and assembling errors of three-ring gear reducer (TRGR) are analyzed. TRGR is a new transmission type whose eccentric phase difference between middle ring plate and side ring plates is 120°. Its mass of middle ring plate is equal to that of side ring plate or 180°, and its mass of middle ring plate is twice of that of side ring plate, which affects load distribution between ring plates. The primary manufacturing and assembling errors include eccentric error of eccentric sheath E_m, internal gear plate E_r and output external gear E_w. A new theoretical method is presented in this paper, which converts load on ring plates into the dedendum bending stress of ring plate to calculate load distribution coefficient (LDC), by means of gap element method(GEM), one of finite element method (FEM). The theoretical calculation and experimental study, which measures ring plate dedendum bending stress by means of sticking strain gauges on the dedendum of middle ring plate internal gear and side ring plate internal gears, are presented. The theoretical calculation and comparison with experiment result of LDC are implemented on two kinds of three-ring gear reducers whose eccentric phase difference between eccentric sheaths is 120° and 180° respectively. The research indicates that the result of theoretical calculation is consistent with that of experimental study. That is to say, the theoretical calculation method is feasible.
基金P.Sun was supported by NSF Grant DMS-1418806C.S.Zhang was partially supported by the National Key Research and Development Program of China(Grant No.2016YFB0201304)+1 种基金the Major Research Plan of National Natural Science Foundation of China(Grant Nos.91430215,91530323)the Key Research Program of Frontier Sciences of CAS.
文摘The distributed Lagrange multiplier/fictitious domain(DLM/FD)-mixed finite element method is developed and analyzed in this paper for a transient Stokes interface problem with jump coefficients.The semi-and fully discrete DLM/FD-mixed finite element scheme are developed for the first time for this problem with a moving interface,where the arbitrary Lagrangian-Eulerian(ALE)technique is employed to deal with the moving and immersed subdomain.Stability and optimal convergence properties are obtained for both schemes.Numerical experiments are carried out for different scenarios of jump coefficients,and all theoretical results are validated.
基金supported by the National Natural Science Foundation of China(No.22076211)the National Key R&D Program of China(No.2017YFF0211203)。
文摘While the spatial distribution pattern of fish is increasingly used for toxicological test o chemicals or wastewater,no ideal parameter is available for quantitative assessment of spa tial distribution,especially uneven distribution with multiple hotspots.Here,to develop a quantitative assessment parameter for spatial distribution,the zebrafish were exposed to ethanol,pentylenetetrazole(PTZ),paraquat dichloride(paraquat)and wastewater,followed by a behavioral test in a narrow tank.Behavioral data was acquired and analyzed by id Tracker and MATLAB.By comparing the effects of all treatments on behavior parameters we confirmed that the spatial distribution was more easily altered rather than general loco motor parameters,e.g.0.7-70 mg/L PTZ and 5-20 mg/L paraquat being effective for altering spatial distribution but having little effects on general locomotor parameters.Based on the heatmap,i.e.,the cumulative proportion of grids and that of frequency in grids,we calcu lated the behavioral Gini coefficient(G_(b))for quantitative assessment of fish spatial distri bution.The Gini coefficient ranged from zero to 1,with larger values meaning poorer even ness of spatial distribution.Of note,G_(b)showed smaller coefficient of variations(CV)with3%-19%between replicate tanks in all treatments than the highest frequency(4%-79%),dis playing well robustness.Especially,G_(b)addressed the challenge of the complicated heatmap with multiple hotspots.Overall,the behavioral Gini coefficient we established is an idea parameter to quantitatively assess spatial distribution of fish shoal,which is expected to be applied in toxicity testing for chemicals and wastewater and automatic quality monitoring for surface water and aquaculture water.
基金supported by the Guangdong Natural Science of Foundation (No. 8151065003000004)the National Natural Science Foundation of China (No.20807012), and the GIGCAS (No. IS-1048).
文摘Polycyclic aromatic hydrocarbons (PAHs) were measured in precipitation from March to August 2005 in Guangzhou, South China. Fourteen PAHs were studied, and their total concentrations varied from 616.6 to 3486.7 ng/L in dissolved phase and from 403.8 to 3125.5 ng/L in particulate phase. The estimated deposition loading of PAHs was 3568 ug/m^2 during the monitoring period. The deposition of PAHs was a potential source for Pearl River comparing with the contents of surface water. In addition, the high concentration in precipitation here implied that PAHs pollution was a potential environmental problem in Guangzhou. Most precipitation concentrations of PAHs in March (the last month in winter in Guangzhou) were higher than in the other months (in rainy season). PAHs inclined to be adsorbed to particulate phase with the increase of molecular weight in rainwater. Combustion of fossil fuel and biomass might be the major source of PAHs, while the direct leakage or volatilization from petroleum products might be insignificant.
基金supported by the Key Technologies R&D Program of China during the 12th Five-Year Plan period(2012BAD09B01)the National 973 Program of China(2012CB955904)the Project of Food Security and Climate Change in the Asia-Pacific Region:Evaluating Mismatch between Crop Development and Water Availability and Project of National Non-profit Institute Fund,China-Australia(BSRF201206)
文摘Climate change will have important implications in water shore regions,such as Huang-Huai-Hai(3H) plain,where expected warmer and drier conditions might augment crop water demand.Sensitivity analysis is important in understanding the relative importance of climatic variables to the variation in reference evapotranspiration(ET 0).In this study,the 51-yr ET 0 during winter wheat and summer maize growing season were calculated from a data set of daily climate variables in 40 meteorological stations.Sensitivity maps for key climate variables were estimated according to Kriging method and the spatial pattern of sensitivity coefficients for these key variables was plotted.In addition,the slopes of the linear regression lines for sensitivity coefficients were obtained.Results showed that ET 0 during winter wheat growing season accounted for the largest proportion of annual ET 0,due to its long phenological days,while ET 0 was detected to decrease significantly with the magnitude of 0.5 mm yr-1in summer maize growing season.Solar radiation is considered to be the most sensitive and primarily controlling variable for negative trend in ET 0 for summer maize season,and higher sensitive coefficient value of ET 0 to solar radiation and temperature were detected in east part and southwest part of 3H plain respectively.Relative humidity was demonstrated as the most sensitive factor for ET 0 in winter wheat growing season and declining relativity humidity also primarily controlled a negative trend in ET 0,furthermore the sensitivity coefficient to relative humidity increased from west to southeast.The eight sensitivity centrals were all found located in Shandong Province.These ET 0 along with its sensitivity maps under winter wheat-summer maize rotation system can be applied to predict the agricultural water demand and will assist water resources planning and management for this region.
基金funded by the Research on Prevention and Control Technology of Ecological Debris Flow Disasters from Department of Land and Resources of Sichuan Province (Grant No. KJ2018-24)the Natural Science Foundation of China (Grant No. 41772343)+2 种基金the Chinese Academy of Sciences and Organization Department of Sichuan Provincial Party Committee "Light of West China" Program (the key control techniques of glacial debris flow along the Sichuan-Tibet Railway)the Key International S&T Cooperation Projects (Grant No. 2016YFE0122400)the Natural Science Foundation of China (Grant No. 41471011)
文摘Grain composition plays a vital role in impact pressure of debris flow. Current approaches treat debris flow as uniform fluid and almost ignore its granular effects. A series of flume experiments have been carried out to explore the granular influence on the impact process of debris flow by using a contact surface pressure gauge sensor(Tactilus~?, produced by Sensor Products LLC). It is found that the maximum impact pressure for debris flow of low density fluctuates drastically with a long duration time while the fluctuation for flow of high density is short in time, respectively presenting logarithmic and linear form in longitudinal attenuation. This can be ascribed to the turbulence effect in the former and grain collisions and grainfluid interaction in the latter. The horizontal distribution of the impact pressure can be considered as the equivalent distribution. For engineering purposes, the longitudinal distribution of the pressure can be generalized to a triangular distribution, from which a new impact method considering granular effects is proposed.
基金funded by the National Natural Science Foundation of China (30872067)the Youth Foundation of Taiyuan University of Technology (2012L017, 2013T037)
文摘Black locust(Robinia pseudoacacia L.) and Chinese pine(Pinus tabulaeformis Carr.) are two woody plants that are widely planted on the Loess Plateau for controlling soil erosion and land desertification. In this study, we conducted an excavation experiment in 2008 to investigate the overall vertical root distribution characteristics of black locust and Chinese pine. We also performed triaxial compression tests to evaluate the root cohesion(additional soil cohesion increased by roots) of black locust. Two types of root distribution, namely, vertical root(VR) and horizontal root(HR), were used as samples and tested under four soil water content(SWC) conditions(12.7%, 15.0%, 18.0% and 20.0%, respectively). Results showed that the root lengths of the two species were mainly concentrated in the root diameter of 5–20 mm. A comparison of root distribution between the two species indicated that the root length of black locust was significantly greater than that of Chinese pine in nearly all root diameters, although the black locust used in the comparison was 10 years younger than the Chinese pine. Root biomass was also significantly greater in black locust than in Chinese pine, particularly in the root diameters of 3–5 and 5–10 mm. These two species were both found to be deep-rooted. The triaxial compression tests showed that root cohesion was greater in the VR samples than in the HR samples. SWC was negatively related to both soil shear strength and root cohesion. These results could provide useful information on the architectural characteristics of woody root system and expand the knowledge on shallow slope stabilization and soil erosion control by plant roots on the Loess Plateau.
基金Project supported by the Hi-Tech Research and Development Program (863) of China(No.2002AA601013).
文摘Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone (ATE) of Taihu Lake were investigated, and the relations among N, P, ORP (oxidation reduction potential), TOC, root system biomass and microorganism were studied. As a whole, significant declines in TN, NO3^--N, DON (dissolved organic nitrogen) and TP concentration in soil solution have occurred with increase of the depth, and reached their minima at 60 cm depth, except for NH4^+-N, which increased with depth. The concentration of TP increased gradually from spring to winter in the topsoil, the maximum 0.08 mg/L presented in the winter while the minimum 0.03 mg/L in spring. In the deeper layer, the concentration value of TP fluctuated little. As for the NO3^--N, its seasonal variation was significant at 20 cm depth, its concentration increased gradually from spring to autumn, and decreased markedly in winter. Vertical and temporal distribution of DON is contrary to that of NO3^--N. The results also show that the variation of N and P in the percolate between adjacent layers is obviously different. The vertical variation ofTN, TP, NO3^--N, NH4^+-N and DON is significant, of which the variation coefficient of NO3^--N along the depth reaches 100.23%, the highest; while the variation coefficient of DON is 41.14%, the smallest. The results of correlation analysis show that the concentration of nitrogen and phosphorus correlate significantly with TOC, ORP, root biomass and counts of nitrifying bacteria. Most nutrients altered much from 20 to 40 cm along the depth. However, DON changed more between 60 and 80 cm. Results show that soil of 0-60 cm depth is active rhizoplane, with strong capability to remove the nitrogen and phosphorus in ATE. It may suggest that there exists the optimum ecological efficiency in the depth of above 60 cm in reed wetland. This will be very significant for ecological restoration and reestablishment.
基金funded by China CDC’s Public Health and Emergency Response Mechanism Programme[131031001000150001]。
文摘Objective Allocation of human resources to address inequalities in the public health system has increasingly attracted societal and political attention.Using the Centers for Disease Control and Prevention(CDCs)system of China as an example,we evaluated inequality in the public health workforce distribution across different regions in China between 2008 and 2017,with the aim of providing information for policymakers to support resource allocation and address growing health inequities.Methods We used three standard public health workforce inequality indices-Gini coefficient,Theil L,and Theil T-and spatial autocorrelation analysis to explore spatial clusters of the workforce in different provinces,visualized with geographical tools.Results The aggregate workforce-to-population ratio decreased from 1.47 to 1.42 per 10,000 population from 2008 to 2017,and was consistently lower than the National Health Commission’s(NHC)recommended critical shortage threshold of 1.75.The workforce distribution inequality indices varied by regional socioeconomic and health system development.Geographic clustering of CDCs workforce distribution was evident,with H–H and L–L clusters in western China and the Guangdong-Fujian region,respectively.Conclusions Our study addressed key issues for government and policymakers in allocation of public health human resources.There is an urgent need for careful identification of analytic questions that will help carry out public health functions in the new era,alongside policy implications for an equitable distribution of the public health workforce focusing on the western region and low–low cluster areas.