China’s economy is expected to remain stable throughout 2025.According to projections by the Center for Forecasting Science of the Academy of Mathematics and Systems Science under the Chinese Academy of Sciences,Chin...China’s economy is expected to remain stable throughout 2025.According to projections by the Center for Forecasting Science of the Academy of Mathematics and Systems Science under the Chinese Academy of Sciences,China’s GDP(gross domestic product)growth should settle at around 4.8 percent this year and will likely hit 5 percent if the government’s stimulus package is effectively implemented.I personally believe that the Chinese economy will maintain growth of about 4.6 percent in 2025 with robust performance in the first and fourth quarters and slower economic activity in the second and third quarters.展开更多
The viscosity of anti-irradiated glass was quantitatively characterized using beam bending viscometry(BBV),parallel plate viscometry(PPV),and rotational viscometry(RV).The Vogel-Fulcher-Tammann(VFT)equation was determ...The viscosity of anti-irradiated glass was quantitatively characterized using beam bending viscometry(BBV),parallel plate viscometry(PPV),and rotational viscometry(RV).The Vogel-Fulcher-Tammann(VFT)equation was determined to be the most suitable for representing the viscosity-temperature characteristics of anti-irradiation glass by comparing the fitting effects and accuracy of different equations within different test ranges.The fragility index m of anti-irradiation glass was 47.5,as calculated using an Angell plot,and the cause of the appropriate fit of the VFT equation was analyzed.The effects of different heating temperatures and loading rates on the tensile properties of glass were studied using a universal testing machine.The results indicated that,at a tensile rate of 10 mm/s,the heating temperature increased from 903 to 1023 K,and the deformation process of anti-irradiation glass transitioned from unstable to stable.When the tensile rate increased from 10 to 30 mm/s at 1023 K,the deformation process of the glass was extremely unstable.This work provides theoretical guidance for the large-size preparation of flexible anti-irradiation glass.展开更多
Bends contribute to a flexible layout of pipeline system,but also lead to intensive energy costs due to the complex flow characteristic.This experimental study is conducted to investigate the impact of a single coarse...Bends contribute to a flexible layout of pipeline system,but also lead to intensive energy costs due to the complex flow characteristic.This experimental study is conducted to investigate the impact of a single coarse particle on the flow field in a bend.The velocity profiles of fluid on the axial symmetry plane of the bend are measured using time-resolved particle image velocimetry.The flow structures are extracted using the proper orthogonal decomposition method.The results reveal that there is a shear-layer flow in the bend during the transportation.With the increase in particle size,the particle has a dominant influence on the flow energy distribution of the overall flow.The impact of particles on the first few energetic flows is mainly in the latter part of the transportation,both temporally and spatially.As the particle size decreases,the most energetic unsteady flow within the bend changes from the convective flow to the flow of the shear layer.展开更多
This study experimentally investigates the hydrodynamic characteristics,geometric configurations,fluttering motions of the codend,and the instantaneous flow fields inside and around the codend,with and without a liner...This study experimentally investigates the hydrodynamic characteristics,geometric configurations,fluttering motions of the codend,and the instantaneous flow fields inside and around the codend,with and without a liner,under varying catch sizes and inflow velocities.A proper orthogonal decomposition method is employed to extract phase-averaged mean properties of unsteady turbulent flows from flow measurement data obtained using an electromagnetic current velocity meter inside and around the codend.The results reveal that as catch size increases,the drag force,codend motion,Reynolds number,and codend volume increase while the drag coefficient decreases.Owing to the codend shape and pronounced motion,a complex fluid–structure interaction occurs,demonstrating a strong correlation between drag force and codend volume.The oscillation amplitudes of the hydrodynamic forces and codend motions increase with increasing catch size,and their oscillations mainly involve low-frequency activity.A significant reduction in the flow field occurs inside and around the unlined codend without a catch.The flow field is 5.81%,14.39%,and 27.01%lower than the unlined codend with a catch,the codend with a liner but without a catch,and the codend with both a liner and a catch,respectively.Fourier analysis reveals that the codend motions and hydrodynamic forces are mainly characterized by low-frequency activity and are synchronized with the unsteady turbulent flow street.Furthermore,the proper orthogonal decomposition results reveal the development of unsteady turbulent flow inside and around the codend,driven by flow passage blockage caused by the presence of the liner,intense codend motions,and the catch.Understanding the hydrodynamic characteristics and flow instabilities inside and around the codend,particularly those associated with its fluttering motions,is crucial for optimizing trawl design and improving trawl selectivity.展开更多
A proper conflict-free k-coloring of a graph is a proper k-coloring in which each nonisolated vertex has a color that appears ex-actly once in its open neighborhood.A graph is PCF k-colorable if it admits a proper con...A proper conflict-free k-coloring of a graph is a proper k-coloring in which each nonisolated vertex has a color that appears ex-actly once in its open neighborhood.A graph is PCF k-colorable if it admits a proper conflict-free k-coloring.The PCF chromatic number of a graph G,denoted by χ_(pcf)(G),is the minimum k such that G is PCF k-colorable.Caro et al conjectured that for a connected graph G with maximum degreeΔ≥3,χ_(pcf)(G)≤Δ+1.One case in this conjecture,a connected graph with maximum degree 3 is PCF 4-colorable,can be derived from the result of Liu and Yu.Jiménez et al stated that the upper bound of PCF chromatic number of a graph G is max{5,x(G)}without a proof.In this paper,we give new proofs of the two results above and derive that for a connected graph G with maximum degreeΔ≥3,its complete subdivision is PCF(Δ+1)-colorable.展开更多
Jacket platforms constitute the foundational infrastructure of offshore oil and gas field exploitation.How to efficiently and accurately monitor the mechanical properties of jacket structures is one of the key problem...Jacket platforms constitute the foundational infrastructure of offshore oil and gas field exploitation.How to efficiently and accurately monitor the mechanical properties of jacket structures is one of the key problems to be solved to ensure the safe operation of the platform.To address the practical engineering problem that it is difficult to monitor the stress response of the tubular joints of jacket platforms online,a digital twin reduced-order method for real-time prediction of the stress response of tubular joints is proposed.In the offline construction phase,multi-scale modeling and multi-parameter experimental design methods are used to obtain the stress response data set of the jacket structure.Proper orthogonal decomposition is employed to extract the main feature information from the snapshot matrix,resulting in a reduced-order basis.The leave-one-out cross-validation method is used to select the optimal modal order for constructing the reduced-order model(ROM).In the online prediction phase,a digital twin model of the tubular joint is established,and the prediction performance of the ROM is analyzed and verified through using random environmental load and field environmental monitoring data.The results indicate that,compared with traditional numerical simulations of tubular joints,the ROM based on the proposed reduced-order method is more efficient in predicting the stress response of tubular joints while ensuring accuracy and robustness.展开更多
A novel gappy technology, gappy autoencoder with proper orthogonal decomposition(Gappy POD-AE), is proposed for reconstructing physical fields from sparse data. High-dimensional data are reduced via proper orthogonal ...A novel gappy technology, gappy autoencoder with proper orthogonal decomposition(Gappy POD-AE), is proposed for reconstructing physical fields from sparse data. High-dimensional data are reduced via proper orthogonal decomposition(POD),and low-dimensional data are used to train an autoencoder(AE). By integrating the POD operator with the decoder, a nonlinear solution form is established and incorporated into a new maximum-a-posteriori(MAP)-based objective for online reconstruction.The numerical results on the two-dimensional(2D) Bhatnagar-Gross-Krook-Boltzmann(BGK-Boltzmann) equation, wave equation, shallow-water equation, and satellite data show that Gappy POD-AE achieves higher accuracy than gappy proper orthogonal decomposition(Gappy POD), especially for the data with slowly decaying singular values,and is more efficient in training than gappy autoencoder(Gappy AE). The MAP-based formulation and new gappy procedure further enhance the reconstruction accuracy.展开更多
The Chinese Space Station Survey Telescope(CSST)presents significant potential for high-precision astrometry.In this study,we show that the point-spread function(PSF)modeled by the discrete PSF with Multi-Gaussian fun...The Chinese Space Station Survey Telescope(CSST)presents significant potential for high-precision astrometry.In this study,we show that the point-spread function(PSF)modeled by the discrete PSF with Multi-Gaussian function can effectively enhance the astrometric accuracy.We determine that the PSF profile can be accurately modeled by three Gaussians,which takes advantage of reduced computational complexity in PSF convolution.In sparse star fields,the lowest centering accuracy we obtain after aberration correction can be below 1 mas.We find that the proper motion errors remain below 1.0 mas yr^(-1)for point sources with five observations and approximately 0.8 mas yr^(-1)for seven observations with a time baseline of around 3.5 yr.We finally demonstrate that the precision of our position measurements for stars fainter than 21 mag in the simulated CSST crowded field is better than the results from both SExtractor and DOLPHOT.展开更多
The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize...The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize the periodic porous dielectrics by transversely isotropic symmetry. The theoretical deductions of SAW propagating in the low-k film/Si substrate layered structure are given in detail. The dispersive characteristics of SAW in differ- ent propagation directions and the effects of the Young＇s moduli E, E′ and shear modulus G′ of the films on these dispersive curves are found. Computational results show that E′ and G′ cannot be measured along the propagation direction that is perpendicular to the nano-pores＇ direction.展开更多
AIM:To determine an optimal cutoff value for abnormal splenic artery diameter/proper hepatic artery diameter(S/P) ratio in cirrhosis-induced portal hypertension.METHODS:Patients with cirrhosis and portal hypertension(...AIM:To determine an optimal cutoff value for abnormal splenic artery diameter/proper hepatic artery diameter(S/P) ratio in cirrhosis-induced portal hypertension.METHODS:Patients with cirrhosis and portal hypertension(n = 770) and healthy volunteers(n = 31) underwent volumetric computed tomography threedimensional vascular reconstruction to measure the internal diameters of the splenic artery and proper hepatic artery to calculate the S/P ratio.The cutoff value for abnormal S/P ratio was determined using receiver operating characteristic curve analysis,and the prevalence of abnormal S/P ratio and associations between abnormal S/P ratio and major complications of portal hypertension were studied using logistic regression.RESULTS:The receiver operating characteristic analysis showed that the cutoff points for abnormal splenic artery internal diameter and S/P ratio were > 5.19 mm and > 1.40,respectively.The sensitivity,specificity,positive predictive value,and negative predictive value were 74.2%,45.2%,97.1%,and 6.6%,respectively.The prevalence of an abnormal S/P ratio in the patients with cirrhosis and portal hypertension was 83.4%.Patients with a higher S/P ratio had a lower risk of developing ascites [odds ratio(OR) = 0.708,95%CI:0.508-0.986,P = 0.041] and a higher risk of developing esophageal and gastric varices(OR = 1.483,95%CI:1.010-2.175,P = 0.044) and forming collateral circulation(OR = 1.518,95%CI:1.033-2.230,P = 0.034).After splenectomy,the portal venous pressure and maximum and mean portal venous flow velocities were reduced,while the flow rate and maximum and minimum flow velocities of the hepatic artery were increased(P < 0.05).CONCLUSION:The prevalence of an abnormal S/P ratio is high in patients with cirrhosis and portal hypertension,and it can be used as an important marker of splanchnic hemodynamic disturbances.展开更多
The Three-River Headwaters region in China is an ecological barrier providing en- vironmental protection and regional sustainable development for the mid-stream and down- stream areas, which also plays an important ro...The Three-River Headwaters region in China is an ecological barrier providing en- vironmental protection and regional sustainable development for the mid-stream and down- stream areas, which also plays an important role in animal husbandry in China. This study estimated the grassland yield in the Three-River Headwaters region based on MODIS NPP data, and calculated the proper livestock-carrying capacity of the grassland. We analyzed the overgrazing number and its spatial distribution characteristics through data comparison be- tween actual and proper livestock-carrying capacity. The results showed the following： （1） total grassland yield （hay） in the Three-River Headwaters region was 10.96 million tons in 2010 with an average grassland yield of 465.70 kg/hm2 （the spatial distribution presents a decreasing trend from the east and southeast to the west and northwest in turn）; （2） the proper livestock-carrying capacity in the Three-River Headwaters region is 12.19 million sheep units （hereafter described as ＂SU＂）, and the average stocking capacity is 51.27 SU [the proper carrying capacity is above 100 SU/km2 in the eastern counties, 60 SU/km2 in the cen- tral counties （except Madoi County）, and 30 SU/km2 in the western counties]; and （3） total overgrazing number was 6.52 million SU in the Three-River Headwaters region in 2010, with an average overgrazing ratio of 67.88% and an average overgrazing number of 27.43 SU/km2 A higher overgrazing ratio occurred in Tongde, Xinghai, Yushu, Henan and Z^kog. There was no overgrazing in Zhiduo, Tanggula Township and Darlag, Qumerleb and Madoi. The re- mainder of the counties had varying degrees of overgrazing.展开更多
Proper meshing of Hy-Vo silent chain and sprocket is important for realizing the transmission of the silent chain with more efficiency and less noise. Based on the study of the meshing theory of the Hy-Vo silent chain...Proper meshing of Hy-Vo silent chain and sprocket is important for realizing the transmission of the silent chain with more efficiency and less noise. Based on the study of the meshing theory of the Hy-Vo silent chain with the sprocket and the roll cutting machining principle of the sprocket with the hob, the proper conditions of the meshing for the Hy-Vo silent chain and the sprocket are put forward with the variable pitch characteristic of the Hy-Vo silent chain taken into consideration, and the proper meshing design method on the condition that the value of the link tooth pressure angle is unequal to the value of the sprocket tooth pressure angle is studied. Experiments show that this new design method is feasible. In addition, the design of the pitch, the sprocket tooth pressure angle and the fillet radius of the sprocket addendum circle are studied. It is crucial for guiding the design of the hob which cuts the Hy-Vo silent chain sprocket.展开更多
In aerodynamic optimization, global optimization methods such as genetic algorithms are preferred in many cases because of their advantage on reaching global optimum. However,for complex problems in which large number...In aerodynamic optimization, global optimization methods such as genetic algorithms are preferred in many cases because of their advantage on reaching global optimum. However,for complex problems in which large number of design variables are needed, the computational cost becomes prohibitive, and thus original global optimization strategies are required. To address this need, data dimensionality reduction method is combined with global optimization methods, thus forming a new global optimization system, aiming to improve the efficiency of conventional global optimization. The new optimization system involves applying Proper Orthogonal Decomposition（POD） in dimensionality reduction of design space while maintaining the generality of original design space. Besides, an acceleration approach for samples calculation in surrogate modeling is applied to reduce the computational time while providing sufficient accuracy. The optimizations of a transonic airfoil RAE2822 and the transonic wing ONERA M6 are performed to demonstrate the effectiveness of the proposed new optimization system. In both cases, we manage to reduce the number of design variables from 20 to 10 and from 42 to 20 respectively. The new design optimization system converges faster and it takes 1/3 of the total time of traditional optimization to converge to a better design, thus significantly reducing the overall optimization time and improving the efficiency of conventional global design optimization method.展开更多
Some properties of convex cones are obtained and are used to derive several equivalent conditions as well as another important property for nearly cone-subconvexlike set-valued functions. Under the assumption of nearl...Some properties of convex cones are obtained and are used to derive several equivalent conditions as well as another important property for nearly cone-subconvexlike set-valued functions. Under the assumption of nearly cone-subconvexlikeness,a Lagrangian multiplier theorem on Benson proper efficiency is presented. Related results are generalized.展开更多
文摘China’s economy is expected to remain stable throughout 2025.According to projections by the Center for Forecasting Science of the Academy of Mathematics and Systems Science under the Chinese Academy of Sciences,China’s GDP(gross domestic product)growth should settle at around 4.8 percent this year and will likely hit 5 percent if the government’s stimulus package is effectively implemented.I personally believe that the Chinese economy will maintain growth of about 4.6 percent in 2025 with robust performance in the first and fourth quarters and slower economic activity in the second and third quarters.
基金Funded by the China Building Material Federation Projects(Nos.20221JBGS06-19,2023JBGS02-01)the National Natural Science Foundation of China(No.U2241236)。
文摘The viscosity of anti-irradiated glass was quantitatively characterized using beam bending viscometry(BBV),parallel plate viscometry(PPV),and rotational viscometry(RV).The Vogel-Fulcher-Tammann(VFT)equation was determined to be the most suitable for representing the viscosity-temperature characteristics of anti-irradiation glass by comparing the fitting effects and accuracy of different equations within different test ranges.The fragility index m of anti-irradiation glass was 47.5,as calculated using an Angell plot,and the cause of the appropriate fit of the VFT equation was analyzed.The effects of different heating temperatures and loading rates on the tensile properties of glass were studied using a universal testing machine.The results indicated that,at a tensile rate of 10 mm/s,the heating temperature increased from 903 to 1023 K,and the deformation process of anti-irradiation glass transitioned from unstable to stable.When the tensile rate increased from 10 to 30 mm/s at 1023 K,the deformation process of the glass was extremely unstable.This work provides theoretical guidance for the large-size preparation of flexible anti-irradiation glass.
基金supported by the Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City(Grant No.2021CXLH0003)the Innovational Fund for Scientific and Technological Personnel of Hainan Province(Grant No.KJRC2023D37).
文摘Bends contribute to a flexible layout of pipeline system,but also lead to intensive energy costs due to the complex flow characteristic.This experimental study is conducted to investigate the impact of a single coarse particle on the flow field in a bend.The velocity profiles of fluid on the axial symmetry plane of the bend are measured using time-resolved particle image velocimetry.The flow structures are extracted using the proper orthogonal decomposition method.The results reveal that there is a shear-layer flow in the bend during the transportation.With the increase in particle size,the particle has a dominant influence on the flow energy distribution of the overall flow.The impact of particles on the first few energetic flows is mainly in the latter part of the transportation,both temporally and spatially.As the particle size decreases,the most energetic unsteady flow within the bend changes from the convective flow to the flow of the shear layer.
基金sponsored by the National Natural Science Foundation of China(Grant No.32373187)the Research Fund for International Scientists of the National Natural Science Foundation of China(Grant No.32350410404)the Natural Science Foundation of Shanghai(Grant No.23ZR1427000).
文摘This study experimentally investigates the hydrodynamic characteristics,geometric configurations,fluttering motions of the codend,and the instantaneous flow fields inside and around the codend,with and without a liner,under varying catch sizes and inflow velocities.A proper orthogonal decomposition method is employed to extract phase-averaged mean properties of unsteady turbulent flows from flow measurement data obtained using an electromagnetic current velocity meter inside and around the codend.The results reveal that as catch size increases,the drag force,codend motion,Reynolds number,and codend volume increase while the drag coefficient decreases.Owing to the codend shape and pronounced motion,a complex fluid–structure interaction occurs,demonstrating a strong correlation between drag force and codend volume.The oscillation amplitudes of the hydrodynamic forces and codend motions increase with increasing catch size,and their oscillations mainly involve low-frequency activity.A significant reduction in the flow field occurs inside and around the unlined codend without a catch.The flow field is 5.81%,14.39%,and 27.01%lower than the unlined codend with a catch,the codend with a liner but without a catch,and the codend with both a liner and a catch,respectively.Fourier analysis reveals that the codend motions and hydrodynamic forces are mainly characterized by low-frequency activity and are synchronized with the unsteady turbulent flow street.Furthermore,the proper orthogonal decomposition results reveal the development of unsteady turbulent flow inside and around the codend,driven by flow passage blockage caused by the presence of the liner,intense codend motions,and the catch.Understanding the hydrodynamic characteristics and flow instabilities inside and around the codend,particularly those associated with its fluttering motions,is crucial for optimizing trawl design and improving trawl selectivity.
基金Supported by the Youth Fund of Lanzhou Jiaotong University(1200061328)。
文摘A proper conflict-free k-coloring of a graph is a proper k-coloring in which each nonisolated vertex has a color that appears ex-actly once in its open neighborhood.A graph is PCF k-colorable if it admits a proper conflict-free k-coloring.The PCF chromatic number of a graph G,denoted by χ_(pcf)(G),is the minimum k such that G is PCF k-colorable.Caro et al conjectured that for a connected graph G with maximum degreeΔ≥3,χ_(pcf)(G)≤Δ+1.One case in this conjecture,a connected graph with maximum degree 3 is PCF 4-colorable,can be derived from the result of Liu and Yu.Jiménez et al stated that the upper bound of PCF chromatic number of a graph G is max{5,x(G)}without a proof.In this paper,we give new proofs of the two results above and derive that for a connected graph G with maximum degreeΔ≥3,its complete subdivision is PCF(Δ+1)-colorable.
基金financially supported by the National Natural Science Foundation of China(Grant No.11472076).
文摘Jacket platforms constitute the foundational infrastructure of offshore oil and gas field exploitation.How to efficiently and accurately monitor the mechanical properties of jacket structures is one of the key problems to be solved to ensure the safe operation of the platform.To address the practical engineering problem that it is difficult to monitor the stress response of the tubular joints of jacket platforms online,a digital twin reduced-order method for real-time prediction of the stress response of tubular joints is proposed.In the offline construction phase,multi-scale modeling and multi-parameter experimental design methods are used to obtain the stress response data set of the jacket structure.Proper orthogonal decomposition is employed to extract the main feature information from the snapshot matrix,resulting in a reduced-order basis.The leave-one-out cross-validation method is used to select the optimal modal order for constructing the reduced-order model(ROM).In the online prediction phase,a digital twin model of the tubular joint is established,and the prediction performance of the ROM is analyzed and verified through using random environmental load and field environmental monitoring data.The results indicate that,compared with traditional numerical simulations of tubular joints,the ROM based on the proposed reduced-order method is more efficient in predicting the stress response of tubular joints while ensuring accuracy and robustness.
基金supported by the National Natural Science Foundation of China(No.12472197)。
文摘A novel gappy technology, gappy autoencoder with proper orthogonal decomposition(Gappy POD-AE), is proposed for reconstructing physical fields from sparse data. High-dimensional data are reduced via proper orthogonal decomposition(POD),and low-dimensional data are used to train an autoencoder(AE). By integrating the POD operator with the decoder, a nonlinear solution form is established and incorporated into a new maximum-a-posteriori(MAP)-based objective for online reconstruction.The numerical results on the two-dimensional(2D) Bhatnagar-Gross-Krook-Boltzmann(BGK-Boltzmann) equation, wave equation, shallow-water equation, and satellite data show that Gappy POD-AE achieves higher accuracy than gappy proper orthogonal decomposition(Gappy POD), especially for the data with slowly decaying singular values,and is more efficient in training than gappy autoencoder(Gappy AE). The MAP-based formulation and new gappy procedure further enhance the reconstruction accuracy.
基金supported by the China Manned Space Program with grant No.CMS-CSST-2025-A11,No.CMSCSST-2025-A19 and No.CMS-CSST-2021-A08supported by the National Natural Science Foundation of China(NSFC)with grant No.12073047+2 种基金supported by the NSFC with grant Nos.12103062 and 12173046supported by the NSFC with grant Nos.12373033,12447204 and 12542019the science research grants from the China Manned Space Project。
文摘The Chinese Space Station Survey Telescope(CSST)presents significant potential for high-precision astrometry.In this study,we show that the point-spread function(PSF)modeled by the discrete PSF with Multi-Gaussian function can effectively enhance the astrometric accuracy.We determine that the PSF profile can be accurately modeled by three Gaussians,which takes advantage of reduced computational complexity in PSF convolution.In sparse star fields,the lowest centering accuracy we obtain after aberration correction can be below 1 mas.We find that the proper motion errors remain below 1.0 mas yr^(-1)for point sources with five observations and approximately 0.8 mas yr^(-1)for seven observations with a time baseline of around 3.5 yr.We finally demonstrate that the precision of our position measurements for stars fainter than 21 mag in the simulated CSST crowded field is better than the results from both SExtractor and DOLPHOT.
文摘The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize the periodic porous dielectrics by transversely isotropic symmetry. The theoretical deductions of SAW propagating in the low-k film/Si substrate layered structure are given in detail. The dispersive characteristics of SAW in differ- ent propagation directions and the effects of the Young＇s moduli E, E′ and shear modulus G′ of the films on these dispersive curves are found. Computational results show that E′ and G′ cannot be measured along the propagation direction that is perpendicular to the nano-pores＇ direction.
基金Supported by Grants from Beijing Municipal Health Bureau, No.2011-2-18the Capital Health Development Special Funds, No.2011-2018-03
文摘AIM:To determine an optimal cutoff value for abnormal splenic artery diameter/proper hepatic artery diameter(S/P) ratio in cirrhosis-induced portal hypertension.METHODS:Patients with cirrhosis and portal hypertension(n = 770) and healthy volunteers(n = 31) underwent volumetric computed tomography threedimensional vascular reconstruction to measure the internal diameters of the splenic artery and proper hepatic artery to calculate the S/P ratio.The cutoff value for abnormal S/P ratio was determined using receiver operating characteristic curve analysis,and the prevalence of abnormal S/P ratio and associations between abnormal S/P ratio and major complications of portal hypertension were studied using logistic regression.RESULTS:The receiver operating characteristic analysis showed that the cutoff points for abnormal splenic artery internal diameter and S/P ratio were > 5.19 mm and > 1.40,respectively.The sensitivity,specificity,positive predictive value,and negative predictive value were 74.2%,45.2%,97.1%,and 6.6%,respectively.The prevalence of an abnormal S/P ratio in the patients with cirrhosis and portal hypertension was 83.4%.Patients with a higher S/P ratio had a lower risk of developing ascites [odds ratio(OR) = 0.708,95%CI:0.508-0.986,P = 0.041] and a higher risk of developing esophageal and gastric varices(OR = 1.483,95%CI:1.010-2.175,P = 0.044) and forming collateral circulation(OR = 1.518,95%CI:1.033-2.230,P = 0.034).After splenectomy,the portal venous pressure and maximum and mean portal venous flow velocities were reduced,while the flow rate and maximum and minimum flow velocities of the hepatic artery were increased(P < 0.05).CONCLUSION:The prevalence of an abnormal S/P ratio is high in patients with cirrhosis and portal hypertension,and it can be used as an important marker of splanchnic hemodynamic disturbances.
基金The Chinese National Non-profit Program for Environment Protection,No.201109030
文摘The Three-River Headwaters region in China is an ecological barrier providing en- vironmental protection and regional sustainable development for the mid-stream and down- stream areas, which also plays an important role in animal husbandry in China. This study estimated the grassland yield in the Three-River Headwaters region based on MODIS NPP data, and calculated the proper livestock-carrying capacity of the grassland. We analyzed the overgrazing number and its spatial distribution characteristics through data comparison be- tween actual and proper livestock-carrying capacity. The results showed the following： （1） total grassland yield （hay） in the Three-River Headwaters region was 10.96 million tons in 2010 with an average grassland yield of 465.70 kg/hm2 （the spatial distribution presents a decreasing trend from the east and southeast to the west and northwest in turn）; （2） the proper livestock-carrying capacity in the Three-River Headwaters region is 12.19 million sheep units （hereafter described as ＂SU＂）, and the average stocking capacity is 51.27 SU [the proper carrying capacity is above 100 SU/km2 in the eastern counties, 60 SU/km2 in the cen- tral counties （except Madoi County）, and 30 SU/km2 in the western counties]; and （3） total overgrazing number was 6.52 million SU in the Three-River Headwaters region in 2010, with an average overgrazing ratio of 67.88% and an average overgrazing number of 27.43 SU/km2 A higher overgrazing ratio occurred in Tongde, Xinghai, Yushu, Henan and Z^kog. There was no overgrazing in Zhiduo, Tanggula Township and Darlag, Qumerleb and Madoi. The re- mainder of the counties had varying degrees of overgrazing.
基金This project is supported by National Natural Science Foundation of China(No.50575089).
文摘Proper meshing of Hy-Vo silent chain and sprocket is important for realizing the transmission of the silent chain with more efficiency and less noise. Based on the study of the meshing theory of the Hy-Vo silent chain with the sprocket and the roll cutting machining principle of the sprocket with the hob, the proper conditions of the meshing for the Hy-Vo silent chain and the sprocket are put forward with the variable pitch characteristic of the Hy-Vo silent chain taken into consideration, and the proper meshing design method on the condition that the value of the link tooth pressure angle is unequal to the value of the sprocket tooth pressure angle is studied. Experiments show that this new design method is feasible. In addition, the design of the pitch, the sprocket tooth pressure angle and the fillet radius of the sprocket addendum circle are studied. It is crucial for guiding the design of the hob which cuts the Hy-Vo silent chain sprocket.
基金supported by the National Natural Science Foundation of China (No. 11502211)
文摘In aerodynamic optimization, global optimization methods such as genetic algorithms are preferred in many cases because of their advantage on reaching global optimum. However,for complex problems in which large number of design variables are needed, the computational cost becomes prohibitive, and thus original global optimization strategies are required. To address this need, data dimensionality reduction method is combined with global optimization methods, thus forming a new global optimization system, aiming to improve the efficiency of conventional global optimization. The new optimization system involves applying Proper Orthogonal Decomposition（POD） in dimensionality reduction of design space while maintaining the generality of original design space. Besides, an acceleration approach for samples calculation in surrogate modeling is applied to reduce the computational time while providing sufficient accuracy. The optimizations of a transonic airfoil RAE2822 and the transonic wing ONERA M6 are performed to demonstrate the effectiveness of the proposed new optimization system. In both cases, we manage to reduce the number of design variables from 20 to 10 and from 42 to 20 respectively. The new design optimization system converges faster and it takes 1/3 of the total time of traditional optimization to converge to a better design, thus significantly reducing the overall optimization time and improving the efficiency of conventional global design optimization method.
文摘Some properties of convex cones are obtained and are used to derive several equivalent conditions as well as another important property for nearly cone-subconvexlike set-valued functions. Under the assumption of nearly cone-subconvexlikeness,a Lagrangian multiplier theorem on Benson proper efficiency is presented. Related results are generalized.
