A novel three-ring-core few-mode fiber with large effective area and low nonlinear coefficient is proposed in this paper. The fiber characteristics based on the full-vector finite element method(FEM) with perfect matc...A novel three-ring-core few-mode fiber with large effective area and low nonlinear coefficient is proposed in this paper. The fiber characteristics based on the full-vector finite element method(FEM) with perfect matched layer boundary conditions show that four supermodes with large effective area, low nonlinear coefficient and low differential mode group delay(DMGD) are achieved. With the increase of input wavelength, the effective areas of three-ring-core few-mode fiber are increased, and the nonlinear coefficients are decreased. The bending losses are increased with the increase of input wavelength, and are decreased with the increase of bending radius. Moreover, the proposed fiber performs a nonlinear coefficient and DMGD flattened profile at a large wavelength range.展开更多
Cognitive emergency communication net-works can meet the requirements of large capac-ity,high density and low delay in emergency com-munications.This paper analyzes the properties of emergency users in cognitive emerg...Cognitive emergency communication net-works can meet the requirements of large capac-ity,high density and low delay in emergency com-munications.This paper analyzes the properties of emergency users in cognitive emergency communi-cation networks,designs a multi-objective optimiza-tion and proposes a novel multi-objective bacterial foraging optimization algorithm based on effective area(MOBFO-EA)to maximize the transmission rate while maximizing the lifecycle of the network.In the algorithm,the effective area is proposed to prevent the algorithm from falling into a local optimum,and the diversity and uniformity of the Pareto-optimal solu-tions distributed in the effective area are used to eval-uate the optimization algorithm.Then,the dynamic preservation is used to enhance the competitiveness of excellent individuals and the uniformity and diversity of the Pareto-optimal solutions in the effective area.Finally,the adaptive step size,adaptive moving direc-tion and inertial weight are used to shorten the search time of bacteria and accelerate the optimization con-vergence.The simulation results show that the pro-posed MOBFO-EA algorithm improves the efficiency of the Pareto-optimal solutions by approximately 55%compared with the MOPSO algorithm and by approx-imately 60%compared with the MOBFO algorithm and has the fastest and smoothest convergence.展开更多
Background:Recently,microbotulinum,a new technique that involves injecting botulinum toxin type A(BoNTA)microdroplets into superficial cutaneous tissue,has gained popularity.The precise distribution of BoNTA in the ta...Background:Recently,microbotulinum,a new technique that involves injecting botulinum toxin type A(BoNTA)microdroplets into superficial cutaneous tissue,has gained popularity.The precise distribution of BoNTA in the targeted area profoundly affects outcomes.Many factors may influence the effective area of BoNTA in the dermis.This study aimed to determine the dermal distribution properties of BoNTA to guide microbotulinum injection.Methods:Ten healthy males aged 18–65 years without BoNTA treatment in the previous year were recruited to receive intradermal injections in the chest and back.Ultrasound was used to ensure the intradermal delivery of injections and measure the dermal thickness.The minor iodine starch test was performed at baseline and 3 days,7 days,21 days,1 month,and 2 months after treatment.Results:All participants received intradermal injections.The dermis was thinner on the chest(thickness,0.20±0.03 cm)than on the back(thickness,0.39±0.07 cm)(P<0.05).An injection in the thicker dermis had a significantly smaller effective area at every follow-up visit.The drug concentration did not affect the effective area except at 3 days after treatment.Injection speed did not influence the effective area at any follow-up visits.Conclusion:An injection in a thicker dermis leads to a smaller effective area for intradermal injections.When the BoNTA dose is the same,the drug concentration and injection speed do not matter.展开更多
Protected areas(PAs) have experienced explosive growth in Northwest China over the last three decades, but their effectiveness in representing regional ecological system diversity has not attracted considerable attent...Protected areas(PAs) have experienced explosive growth in Northwest China over the last three decades, but their effectiveness in representing regional ecological system diversity has not attracted considerable attention. Low effectiveness would exacerbate the conservation-development conflicts, particularly those that arise as a result of the Great Western Development Strategy(GWDS). Thus, an assessment of the effectiveness of the PA network has become quite important. We proposed natural vegetation communities to represent regional ecological system diversities, and proposed Global 200 Priority Ecoregions, Important Bird Areas, and ecosystem function regions to represent important conservation areas. To determine their effectiveness, we studied the extent to which ecological system diversities and important conservation areas are represented by the existing 96 PAs. Our results indicated that the total coverage of vegetation communities in PAs in Northwest China is not sufficiently comprehensive. As the PA system has expanded, the growth in the total area of the PAs has been greater than that of their vegetation community richness. While most of the important conservation areas are covered by PAs, some regions have not yet reached the 10% threshold; further, PAs are distributed unevenly and conservation gaps remain in the region. Therefore, these regions should receive more attention when planning new PAs. It is vital that more biodiversity datasets and assessment of ecosystem function regions are integrated in order to provide a basis for the government to formulate appropriate protection and development strategies.展开更多
The size and shape of the effective test area are crucial to consider when short-crested waves are created by segmented wavemakers. The range of the effective test area of short-crested waves simulated by two-sided se...The size and shape of the effective test area are crucial to consider when short-crested waves are created by segmented wavemakers. The range of the effective test area of short-crested waves simulated by two-sided segmented wavemakers is analyzed in this paper. The experimental investigation on the wave field distribution of short-crested waves generated by two-sided segmented wavemakers is conducted by using an array of wave gauges. Wave spectra and directional spreading function are analyzed and the results show that when the main direction is at a certain angle with the normal line of wave generators, the wave field of 3D short-crested waves generated by two-sided segmented wavemakers has good spatial uniformity within the model test area. The effective test area can provide good wave environments for seakeeping model tests of various ocean engineering structures in the deep ocean engineering basin.展开更多
With the artificial alder and cypress mixed forest being planted, there has been a marked land use change since 1970s' in Hilly Area of Central Sichuan Basin, China. Data from meteorological observations or posts ...With the artificial alder and cypress mixed forest being planted, there has been a marked land use change since 1970s' in Hilly Area of Central Sichuan Basin, China. Data from meteorological observations or posts operated over long time, measurement and calculation of NPP (net primary production) and biomass of biological community, and analysis of soil organic matter content show that the artificial alder and cypress mixed forest has outstanding eco-environmental effect: adjusting local climate, raising soil fertility, alleviating menace of drought, and raising NPP and biomass of biological community. It is very beneficial for improving ecological environment to afforest artificial alder and cypress mixed forest in populous Hilly Area of Central Sichuan Basin, China. Key Words: land use/land cover change (LUCC); eco-environmental effect; Hilly Area of Central Sichuan Basin; the artificial alder and cypress mixed forest展开更多
In this paper, the monthly-averaged planetary albedo and equivalent blackbody temperature are calculated by using Gauss-Seidle numerical model to solve the equation of radiative transfer, based on measured aerosol dat...In this paper, the monthly-averaged planetary albedo and equivalent blackbody temperature are calculated by using Gauss-Seidle numerical model to solve the equation of radiative transfer, based on measured aerosol data over Beijing aera. With the increase of atmospheric turbidity, the planetary albedo has different characteristics in different seasons, and there is an evident decrease in the winter season. It means that the local aerosol has an heating effect to the atmosphere in winter. The correlation feature between the surface temperature and the horizontal visibility from 1963 to 1986 is analyzed, and anticorrelation is discovered in winter. It is found that surface temperature increases with the increase of aeresol.展开更多
-Sediment from Xiamen industrial area was added to marine ecosystem enclosures to test the effects on the planktonic communities in Xiamen Bay, China, in April, 1985. Sediments were added at two concentrations, 11.2 a...-Sediment from Xiamen industrial area was added to marine ecosystem enclosures to test the effects on the planktonic communities in Xiamen Bay, China, in April, 1985. Sediments were added at two concentrations, 11.2 and 112 ppm dry wt. respectively. The species of phytoplankton did not change as compared with the control, but the number of diatoms markedly decreased in the sediment treated enclosures. A suppression of photosynthesis was presumed to be due to light attenuation by the added sediment. Microflagellates, zooplankton and bacteria were resistant to sediment increase in water column.展开更多
Relative tillering rate(RTR)increased linear-ly with the increasing of leaf N concentration(NLV)has been already reported.To testwhether this relationship could be used toquantitatively explain the difference in tille...Relative tillering rate(RTR)increased linear-ly with the increasing of leaf N concentration(NLV)has been already reported.To testwhether this relationship could be used toquantitatively explain the difference in tilleringamong a wide range of N application,field ex- periments were conducted at the IRRI farm,Los Banos,Laguna,the Philippines.Two in- dica cultivars,IR 72 and IR68284H wereused.For each cultivar,12 treatments includ- ing 4 N levels(0,60,120,and 180kgN·ha)and 3 transplanting spacing(30×20,20×20,and 10×20cm)were arranged in a ran-domized split-plot design with 4 replications.The N treatments were designated as mainplots and spacings as subplots.Fourteen-day-old seedlings were transplanted with 3seedlings per hill.The subplot area was 20m~2.Nitrogen fertilizer was applied as basal,atmidtillering,and at panicle initiation in threeequal splits.P,K,and Zn were applied asbasal at normal dosage.The field was flooded.Plant samples were taken every 7-14 d from 14d after transplanting to flower展开更多
The wireless signals emitted by base stations serve as a vital link connecting people in today’s society and have been occupying an increasingly important role in real life.The development of the Internet of Things(I...The wireless signals emitted by base stations serve as a vital link connecting people in today’s society and have been occupying an increasingly important role in real life.The development of the Internet of Things(IoT)relies on the support of base stations,which provide a solid foundation for achieving a more intelligent way of living.In a specific area,achieving higher signal coverage with fewer base stations has become an urgent problem.Therefore,this article focuses on the effective coverage area of base station signals and proposes a novel Evolutionary Particle Swarm Optimization(EPSO)algorithm based on collective prediction,referred to herein as ECPPSO.Introducing a new strategy called neighbor-based evolution prediction(NEP)addresses the issue of premature convergence often encountered by PSO.ECPPSO also employs a strengthening evolution(SE)strategy to enhance the algorithm’s global search capability and efficiency,ensuring enhanced robustness and a faster convergence speed when solving complex optimization problems.To better adapt to the actual communication needs of base stations,this article conducts simulation experiments by changing the number of base stations.The experimental results demonstrate thatunder the conditionof 50 ormore base stations,ECPPSOconsistently achieves the best coverage rate exceeding 95%,peaking at 99.4400%when the number of base stations reaches 80.These results validate the optimization capability of the ECPPSO algorithm,proving its feasibility and effectiveness.Further ablative experiments and comparisons with other algorithms highlight the advantages of ECPPSO.展开更多
This study addresses a critical challenge in CFD-DEM simulations:the accurate assignment of drag force to fluid mesh cells when the cell size exceeds particle sizes.Traditional particle centroid method(PCM)approaches ...This study addresses a critical challenge in CFD-DEM simulations:the accurate assignment of drag force to fluid mesh cells when the cell size exceeds particle sizes.Traditional particle centroid method(PCM)approaches often lead to abrupt drag force variations as particles cross cell boundaries due to their discrete nature.To overcome this limitation,we propose a novel algorithm that computes an analytical solution for the effective projected area(EPA)of particles within computational cells,aligned with the relative velocity direction.The drag force is then proportionally scaled according to this EPA calculation.The paper presents a specific implementation case of our algorithm,focusing on scenarios where a cell vertex resides within a particle boundary.For EPA determination,we introduce an innovative classification approach based on face-windward surface relations.Extensive validation involved 100,000 test cases with varying cell-particle relative positions(all constrained by the vertex-in-particle condition),systematically classified into 18 types using our scheme.Results demonstrate that all computed EPA values remain within theoretical bounds,confirming the classification's comprehensiveness.Through 5 classic particle movement simulations,we show that our method maintains continuous EPA variation across time steps-a marked improvement over PCM's characteristic discontinuities.Implementation within the CFD-DEM framework for single-particle sedimentation yields terminal velocities that closely match experimental data while ensuring smooth drag force transitions between fluid cells.Compared to PCM,the present method reduces the relative error in terminal settling velocity by approximately 43%.Moreover,comparative studies of dual-particle sedimentation demonstrate our algorithm's superior performance relative to conventional PCM approaches.For Particle 1,the terminal vertical velocity predicted by the present method reduces the relative error by approximately 17%compared to PCM.These advances significantly enhance simulation fidelity for particle-fluid interaction problems where cell-particle size ratios challenge traditional methods.展开更多
The long baseline （LBL） system is widely used to locate and track autonomous underwater vehicles （AUV） through acoustic communication. Three important issues are presented here in LBL system application with AUV. ...The long baseline （LBL） system is widely used to locate and track autonomous underwater vehicles （AUV） through acoustic communication. Three important issues are presented here in LBL system application with AUV. Those issues which regard the normal acoustic communication between LBL system and AUV are the depth of towed army, the length of beacon cable, and the effective area of the AUV. The first issue is the key of the LBL system, which ensures the normal communication between towed array and beacons. The second issue which impacts the normal communication from the AUV to beacons in available range should be considered after the first one has been settled. Then the last issue determines the safe work area of the AUV. The ordinary differential equations （ODE） algorithm of ray is deduced from Snell＇s law. The ODE algorithm is applied to obtain sound rays from sound source to receiver. These problems are solved by the judgment that whether rays pinging from a sound source arrives at a receiver. The sea trial shows that these methods have much validity and practicality.展开更多
In this paper, a refractive index profile design enabling us to obtain a flat modal field around the fibre centre is investigated. The theoretical approach for designing such multilayer large flattened mode （LFM） op...In this paper, a refractive index profile design enabling us to obtain a flat modal field around the fibre centre is investigated. The theoretical approach for designing such multilayer large flattened mode （LFM） optical fibres is presented. A comparison is made between the properties of a three-layer LFM structure and a standard step-index profile with the same core size. The obtained results indicate that the effective area of the LFM fibre is about twice as large as that of the standard step-index fibre, but the LFM fibre has less effective ability to filter out the higher order modes than the standard step-index fibre with the same bending radius.展开更多
The high power holey fiber is an efficient supercontinuum light source by using picosecond pulse,which is a less expensive laser source compared with low power and expensive femtosecond laser sources. In this paper, a...The high power holey fiber is an efficient supercontinuum light source by using picosecond pulse,which is a less expensive laser source compared with low power and expensive femtosecond laser sources. In this paper, a high power highly nonlinear holey fiber(HN-HF) with a low confinement loss is proposed for supercontinuum light sources. The finite difference method is used to calculate the different properties of the proposed HN-HF. High nonlinear coefficients are obtained at 1.06 μm, 1.31μm, and 1.55μm wavelengths with flattened chromatic dispersion and low confinement losses simultaneously. Moreover, numerical simulation results show that high power broad supercontinuum spectra with very short length of the proposed photonic crystal fiber are achieved.展开更多
[Objective] This study aimed to analyze the cause of the generation of short-term heavy precipitations in a regional heavy rainstorm in Shannxi Province. [Method] Taking a heavy rainstorm covering most parts of Shaanx...[Objective] This study aimed to analyze the cause of the generation of short-term heavy precipitations in a regional heavy rainstorm in Shannxi Province. [Method] Taking a heavy rainstorm covering most parts of Shaanxi Province in late July 2010 as an example, data of five Doppler weather radars in Shaanxi Province were employed for a detailed analysis of the evolution of the heavy rainstorm pro- cess. [Result] Besides the good large-scale weather background conditions, the de- velopment and evolution of some mesoscale and small-scale weather systems direct- ly led to short-term heavy precipitations during the heavy rainstorm process, involv- ing the intrusion of moderate IS-scale weak cold air and presence of small-scale wind shear, convergence and adverse wind area. In addition, small-scale convection echoes were arranged in lines and formed a ＂train effect＂, which would also con- tribute to the generation of short-term heavy precipitation. [Conclusion] This study provided basic information for more clear and in-depth analysis of the formation mechanism of short-term heavy precipitations.展开更多
Too high grinding force will lead to a large increase in specific grinding energy, resulting in high temperature in grinding zone, especially for the aerospace difficult cutting metal materials,seriously affecting the...Too high grinding force will lead to a large increase in specific grinding energy, resulting in high temperature in grinding zone, especially for the aerospace difficult cutting metal materials,seriously affecting the surface quality and accuracy. At present, the theoretical models of grinding force are mostly based on the assumption of uniform or simplified morphological characteristics of grains, which is inconsistent with the actual grains. Especially for non-engineering grinding wheel,most geometric characteristics of grains are ignored, resulting in the calculation accuracy that cannot guide practical production. Based on this, an improved grinding force model based on random grain geometric characteristics is proposed in this paper. Firstly, the surface topography model of CBN grinding wheel is established, and the effective grain determination mechanism in grinding zone is revealed. Based on the known grinding force model and mechanical behavior of interaction between grains and workpiece in different stages, the concept of grain effective action area is proposed. The variation mechanism of effective action area under the influence of grain geometric and spatial characteristics is deeply analyzed, and the calculation method under random combination of five influencing parameters is obtained. The numerical simulation is carried out to reveal the dynamic variation process of grinding force in grinding zone. In order to verify the theoretical model, the experiments of dry grinding Ti-6Al-4 V are designed. The experimental results show that under different machining parameters, the results of numerical calculation and experimental measurement are in good agreement, and the minimum error value is only 2.1 %, which indicates that the calculation accuracy of grinding force model meets the requirements and is feasible. This study will provide a theoretical basis for optimizing the wheel structure, effectively controlling the grinding force range, adjusting the grinding zone temperature and improving the workpiece machining quality in the industrial grinding process.展开更多
One test rig with three blades and two Under-Platform Dampers(UPDs) is established to better understand the dynamical behavior of blades with UPDs. A pre-loaded spring is used to simulate the centrifugal load acting o...One test rig with three blades and two Under-Platform Dampers(UPDs) is established to better understand the dynamical behavior of blades with UPDs. A pre-loaded spring is used to simulate the centrifugal load acting on the damper, thereby achieving continuous adjustment of the pressing load. UPDs with different forms, sizes and materials are carefully designed as experimental control groups. Noncontact measurement via a laser Doppler velocimeter is employed and contact excitation which is performed by an electromagnetic exciter is adopted to directly obtain the magnitude of the excitation load by a force sensor mounted on the excitation rod. Particular attention is paid to the influence of the contact status of the contact surfaces, e.g. the pressure-sensitive paper is used to measure the effective contact area of the UPDs. The experimental variables are selected as the centrifugal force, the amplitude of the excitation force, the damper mass, the effective contact area, and the damper material. The Frequency Response Function(FRF) of the blade under different experimental parameters is obtained by slow frequency sweep under sinusoidal excitation to study the influence of each parameter on the dynamic characteristics of the blade and the mechanism analysis is carried out combined with the experimental results.展开更多
基金supported by the National Natural Science Foundation of China(Nos.61671227 and 61431009)the Shandong Provincial Natural Science Foundation(No.ZR2011FM015)the Taishan Scholar Research Fund of Shandong Province
文摘A novel three-ring-core few-mode fiber with large effective area and low nonlinear coefficient is proposed in this paper. The fiber characteristics based on the full-vector finite element method(FEM) with perfect matched layer boundary conditions show that four supermodes with large effective area, low nonlinear coefficient and low differential mode group delay(DMGD) are achieved. With the increase of input wavelength, the effective areas of three-ring-core few-mode fiber are increased, and the nonlinear coefficients are decreased. The bending losses are increased with the increase of input wavelength, and are decreased with the increase of bending radius. Moreover, the proposed fiber performs a nonlinear coefficient and DMGD flattened profile at a large wavelength range.
基金National Natural Sci-ence Foundation of China(Grant Nos.61871241 and 61771263)Science and Technology Program of Nantong(Grant No.JC2019117).
文摘Cognitive emergency communication net-works can meet the requirements of large capac-ity,high density and low delay in emergency com-munications.This paper analyzes the properties of emergency users in cognitive emergency communi-cation networks,designs a multi-objective optimiza-tion and proposes a novel multi-objective bacterial foraging optimization algorithm based on effective area(MOBFO-EA)to maximize the transmission rate while maximizing the lifecycle of the network.In the algorithm,the effective area is proposed to prevent the algorithm from falling into a local optimum,and the diversity and uniformity of the Pareto-optimal solu-tions distributed in the effective area are used to eval-uate the optimization algorithm.Then,the dynamic preservation is used to enhance the competitiveness of excellent individuals and the uniformity and diversity of the Pareto-optimal solutions in the effective area.Finally,the adaptive step size,adaptive moving direc-tion and inertial weight are used to shorten the search time of bacteria and accelerate the optimization con-vergence.The simulation results show that the pro-posed MOBFO-EA algorithm improves the efficiency of the Pareto-optimal solutions by approximately 55%compared with the MOPSO algorithm and by approx-imately 60%compared with the MOBFO algorithm and has the fastest and smoothest convergence.
基金supported by the National High Level Hospital Clinical Research Funding(grant nos.2022-PUMCH-B-041,2022-PUMCH-A-210,and 2022-PUMCH-C-025).
文摘Background:Recently,microbotulinum,a new technique that involves injecting botulinum toxin type A(BoNTA)microdroplets into superficial cutaneous tissue,has gained popularity.The precise distribution of BoNTA in the targeted area profoundly affects outcomes.Many factors may influence the effective area of BoNTA in the dermis.This study aimed to determine the dermal distribution properties of BoNTA to guide microbotulinum injection.Methods:Ten healthy males aged 18–65 years without BoNTA treatment in the previous year were recruited to receive intradermal injections in the chest and back.Ultrasound was used to ensure the intradermal delivery of injections and measure the dermal thickness.The minor iodine starch test was performed at baseline and 3 days,7 days,21 days,1 month,and 2 months after treatment.Results:All participants received intradermal injections.The dermis was thinner on the chest(thickness,0.20±0.03 cm)than on the back(thickness,0.39±0.07 cm)(P<0.05).An injection in the thicker dermis had a significantly smaller effective area at every follow-up visit.The drug concentration did not affect the effective area except at 3 days after treatment.Injection speed did not influence the effective area at any follow-up visits.Conclusion:An injection in a thicker dermis leads to a smaller effective area for intradermal injections.When the BoNTA dose is the same,the drug concentration and injection speed do not matter.
基金Under the auspices of National Science&Technology Pillar Program During the Twelfth Five-year Plan Period(No.2011BAC09B08)
文摘Protected areas(PAs) have experienced explosive growth in Northwest China over the last three decades, but their effectiveness in representing regional ecological system diversity has not attracted considerable attention. Low effectiveness would exacerbate the conservation-development conflicts, particularly those that arise as a result of the Great Western Development Strategy(GWDS). Thus, an assessment of the effectiveness of the PA network has become quite important. We proposed natural vegetation communities to represent regional ecological system diversities, and proposed Global 200 Priority Ecoregions, Important Bird Areas, and ecosystem function regions to represent important conservation areas. To determine their effectiveness, we studied the extent to which ecological system diversities and important conservation areas are represented by the existing 96 PAs. Our results indicated that the total coverage of vegetation communities in PAs in Northwest China is not sufficiently comprehensive. As the PA system has expanded, the growth in the total area of the PAs has been greater than that of their vegetation community richness. While most of the important conservation areas are covered by PAs, some regions have not yet reached the 10% threshold; further, PAs are distributed unevenly and conservation gaps remain in the region. Therefore, these regions should receive more attention when planning new PAs. It is vital that more biodiversity datasets and assessment of ecosystem function regions are integrated in order to provide a basis for the government to formulate appropriate protection and development strategies.
基金financially supported by the National Natural Science Foundation of China(Grant No.51239007)
文摘The size and shape of the effective test area are crucial to consider when short-crested waves are created by segmented wavemakers. The range of the effective test area of short-crested waves simulated by two-sided segmented wavemakers is analyzed in this paper. The experimental investigation on the wave field distribution of short-crested waves generated by two-sided segmented wavemakers is conducted by using an array of wave gauges. Wave spectra and directional spreading function are analyzed and the results show that when the main direction is at a certain angle with the normal line of wave generators, the wave field of 3D short-crested waves generated by two-sided segmented wavemakers has good spatial uniformity within the model test area. The effective test area can provide good wave environments for seakeeping model tests of various ocean engineering structures in the deep ocean engineering basin.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences(KZCX1-SW-01-01B)Cultivatlon Foundation of Institute of Mountain Hazards and Environment,CAS
文摘With the artificial alder and cypress mixed forest being planted, there has been a marked land use change since 1970s' in Hilly Area of Central Sichuan Basin, China. Data from meteorological observations or posts operated over long time, measurement and calculation of NPP (net primary production) and biomass of biological community, and analysis of soil organic matter content show that the artificial alder and cypress mixed forest has outstanding eco-environmental effect: adjusting local climate, raising soil fertility, alleviating menace of drought, and raising NPP and biomass of biological community. It is very beneficial for improving ecological environment to afforest artificial alder and cypress mixed forest in populous Hilly Area of Central Sichuan Basin, China. Key Words: land use/land cover change (LUCC); eco-environmental effect; Hilly Area of Central Sichuan Basin; the artificial alder and cypress mixed forest
文摘In this paper, the monthly-averaged planetary albedo and equivalent blackbody temperature are calculated by using Gauss-Seidle numerical model to solve the equation of radiative transfer, based on measured aerosol data over Beijing aera. With the increase of atmospheric turbidity, the planetary albedo has different characteristics in different seasons, and there is an evident decrease in the winter season. It means that the local aerosol has an heating effect to the atmosphere in winter. The correlation feature between the surface temperature and the horizontal visibility from 1963 to 1986 is analyzed, and anticorrelation is discovered in winter. It is found that surface temperature increases with the increase of aeresol.
文摘-Sediment from Xiamen industrial area was added to marine ecosystem enclosures to test the effects on the planktonic communities in Xiamen Bay, China, in April, 1985. Sediments were added at two concentrations, 11.2 and 112 ppm dry wt. respectively. The species of phytoplankton did not change as compared with the control, but the number of diatoms markedly decreased in the sediment treated enclosures. A suppression of photosynthesis was presumed to be due to light attenuation by the added sediment. Microflagellates, zooplankton and bacteria were resistant to sediment increase in water column.
文摘Relative tillering rate(RTR)increased linear-ly with the increasing of leaf N concentration(NLV)has been already reported.To testwhether this relationship could be used toquantitatively explain the difference in tilleringamong a wide range of N application,field ex- periments were conducted at the IRRI farm,Los Banos,Laguna,the Philippines.Two in- dica cultivars,IR 72 and IR68284H wereused.For each cultivar,12 treatments includ- ing 4 N levels(0,60,120,and 180kgN·ha)and 3 transplanting spacing(30×20,20×20,and 10×20cm)were arranged in a ran-domized split-plot design with 4 replications.The N treatments were designated as mainplots and spacings as subplots.Fourteen-day-old seedlings were transplanted with 3seedlings per hill.The subplot area was 20m~2.Nitrogen fertilizer was applied as basal,atmidtillering,and at panicle initiation in threeequal splits.P,K,and Zn were applied asbasal at normal dosage.The field was flooded.Plant samples were taken every 7-14 d from 14d after transplanting to flower
基金supported by the National Natural Science Foundation of China(Nos.62272418,62102058)Basic Public Welfare Research Program of Zhejiang Province(No.LGG18E050011)the Major Open Project of Key Laboratory for Advanced Design and Intelligent Computing of the Ministry of Education under Grant ADIC2023ZD001,National Undergraduate Training Program on Innovation and Entrepreneurship(No.202410345054).
文摘The wireless signals emitted by base stations serve as a vital link connecting people in today’s society and have been occupying an increasingly important role in real life.The development of the Internet of Things(IoT)relies on the support of base stations,which provide a solid foundation for achieving a more intelligent way of living.In a specific area,achieving higher signal coverage with fewer base stations has become an urgent problem.Therefore,this article focuses on the effective coverage area of base station signals and proposes a novel Evolutionary Particle Swarm Optimization(EPSO)algorithm based on collective prediction,referred to herein as ECPPSO.Introducing a new strategy called neighbor-based evolution prediction(NEP)addresses the issue of premature convergence often encountered by PSO.ECPPSO also employs a strengthening evolution(SE)strategy to enhance the algorithm’s global search capability and efficiency,ensuring enhanced robustness and a faster convergence speed when solving complex optimization problems.To better adapt to the actual communication needs of base stations,this article conducts simulation experiments by changing the number of base stations.The experimental results demonstrate thatunder the conditionof 50 ormore base stations,ECPPSOconsistently achieves the best coverage rate exceeding 95%,peaking at 99.4400%when the number of base stations reaches 80.These results validate the optimization capability of the ECPPSO algorithm,proving its feasibility and effectiveness.Further ablative experiments and comparisons with other algorithms highlight the advantages of ECPPSO.
基金the National Science and Technology Major Project(2011ZX06901-003)。
文摘This study addresses a critical challenge in CFD-DEM simulations:the accurate assignment of drag force to fluid mesh cells when the cell size exceeds particle sizes.Traditional particle centroid method(PCM)approaches often lead to abrupt drag force variations as particles cross cell boundaries due to their discrete nature.To overcome this limitation,we propose a novel algorithm that computes an analytical solution for the effective projected area(EPA)of particles within computational cells,aligned with the relative velocity direction.The drag force is then proportionally scaled according to this EPA calculation.The paper presents a specific implementation case of our algorithm,focusing on scenarios where a cell vertex resides within a particle boundary.For EPA determination,we introduce an innovative classification approach based on face-windward surface relations.Extensive validation involved 100,000 test cases with varying cell-particle relative positions(all constrained by the vertex-in-particle condition),systematically classified into 18 types using our scheme.Results demonstrate that all computed EPA values remain within theoretical bounds,confirming the classification's comprehensiveness.Through 5 classic particle movement simulations,we show that our method maintains continuous EPA variation across time steps-a marked improvement over PCM's characteristic discontinuities.Implementation within the CFD-DEM framework for single-particle sedimentation yields terminal velocities that closely match experimental data while ensuring smooth drag force transitions between fluid cells.Compared to PCM,the present method reduces the relative error in terminal settling velocity by approximately 43%.Moreover,comparative studies of dual-particle sedimentation demonstrate our algorithm's superior performance relative to conventional PCM approaches.For Particle 1,the terminal vertical velocity predicted by the present method reduces the relative error by approximately 17%compared to PCM.These advances significantly enhance simulation fidelity for particle-fluid interaction problems where cell-particle size ratios challenge traditional methods.
文摘The long baseline （LBL） system is widely used to locate and track autonomous underwater vehicles （AUV） through acoustic communication. Three important issues are presented here in LBL system application with AUV. Those issues which regard the normal acoustic communication between LBL system and AUV are the depth of towed army, the length of beacon cable, and the effective area of the AUV. The first issue is the key of the LBL system, which ensures the normal communication between towed array and beacons. The second issue which impacts the normal communication from the AUV to beacons in available range should be considered after the first one has been settled. Then the last issue determines the safe work area of the AUV. The ordinary differential equations （ODE） algorithm of ray is deduced from Snell＇s law. The ODE algorithm is applied to obtain sound rays from sound source to receiver. These problems are solved by the judgment that whether rays pinging from a sound source arrives at a receiver. The sea trial shows that these methods have much validity and practicality.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10576012 and 60538010）.
文摘In this paper, a refractive index profile design enabling us to obtain a flat modal field around the fibre centre is investigated. The theoretical approach for designing such multilayer large flattened mode （LFM） optical fibres is presented. A comparison is made between the properties of a three-layer LFM structure and a standard step-index profile with the same core size. The obtained results indicate that the effective area of the LFM fibre is about twice as large as that of the standard step-index fibre, but the LFM fibre has less effective ability to filter out the higher order modes than the standard step-index fibre with the same bending radius.
文摘The high power holey fiber is an efficient supercontinuum light source by using picosecond pulse,which is a less expensive laser source compared with low power and expensive femtosecond laser sources. In this paper, a high power highly nonlinear holey fiber(HN-HF) with a low confinement loss is proposed for supercontinuum light sources. The finite difference method is used to calculate the different properties of the proposed HN-HF. High nonlinear coefficients are obtained at 1.06 μm, 1.31μm, and 1.55μm wavelengths with flattened chromatic dispersion and low confinement losses simultaneously. Moreover, numerical simulation results show that high power broad supercontinuum spectra with very short length of the proposed photonic crystal fiber are achieved.
基金Supported by Special Fund for National Weather Service Forecaster of China (CMAYBY2011-050)~~
文摘[Objective] This study aimed to analyze the cause of the generation of short-term heavy precipitations in a regional heavy rainstorm in Shannxi Province. [Method] Taking a heavy rainstorm covering most parts of Shaanxi Province in late July 2010 as an example, data of five Doppler weather radars in Shaanxi Province were employed for a detailed analysis of the evolution of the heavy rainstorm pro- cess. [Result] Besides the good large-scale weather background conditions, the de- velopment and evolution of some mesoscale and small-scale weather systems direct- ly led to short-term heavy precipitations during the heavy rainstorm process, involv- ing the intrusion of moderate IS-scale weak cold air and presence of small-scale wind shear, convergence and adverse wind area. In addition, small-scale convection echoes were arranged in lines and formed a ＂train effect＂, which would also con- tribute to the generation of short-term heavy precipitation. [Conclusion] This study provided basic information for more clear and in-depth analysis of the formation mechanism of short-term heavy precipitations.
基金supported by the National Natural Science Foundation of China(Nos.51975305,51905289,52105264)the Key Project of Shandong Province,China(No.ZR2020KE027)+1 种基金the Major Research Project of Shandong Province,China(Nos.2019GGX104040 and 2019GSF108236)the Natural Science Foundation of Shandong Province,China(No.ZR2021QE116).
文摘Too high grinding force will lead to a large increase in specific grinding energy, resulting in high temperature in grinding zone, especially for the aerospace difficult cutting metal materials,seriously affecting the surface quality and accuracy. At present, the theoretical models of grinding force are mostly based on the assumption of uniform or simplified morphological characteristics of grains, which is inconsistent with the actual grains. Especially for non-engineering grinding wheel,most geometric characteristics of grains are ignored, resulting in the calculation accuracy that cannot guide practical production. Based on this, an improved grinding force model based on random grain geometric characteristics is proposed in this paper. Firstly, the surface topography model of CBN grinding wheel is established, and the effective grain determination mechanism in grinding zone is revealed. Based on the known grinding force model and mechanical behavior of interaction between grains and workpiece in different stages, the concept of grain effective action area is proposed. The variation mechanism of effective action area under the influence of grain geometric and spatial characteristics is deeply analyzed, and the calculation method under random combination of five influencing parameters is obtained. The numerical simulation is carried out to reveal the dynamic variation process of grinding force in grinding zone. In order to verify the theoretical model, the experiments of dry grinding Ti-6Al-4 V are designed. The experimental results show that under different machining parameters, the results of numerical calculation and experimental measurement are in good agreement, and the minimum error value is only 2.1 %, which indicates that the calculation accuracy of grinding force model meets the requirements and is feasible. This study will provide a theoretical basis for optimizing the wheel structure, effectively controlling the grinding force range, adjusting the grinding zone temperature and improving the workpiece machining quality in the industrial grinding process.
基金the financial support from the National Natural Science Foundation of China (Nos. 11772022, 91860205 and 51475021)the experimental devices provided by Key Laboratory of Vibration and Control of Aero-Propulsion System, Ministry of Education, Northeastern University (VCAME201602)
文摘One test rig with three blades and two Under-Platform Dampers(UPDs) is established to better understand the dynamical behavior of blades with UPDs. A pre-loaded spring is used to simulate the centrifugal load acting on the damper, thereby achieving continuous adjustment of the pressing load. UPDs with different forms, sizes and materials are carefully designed as experimental control groups. Noncontact measurement via a laser Doppler velocimeter is employed and contact excitation which is performed by an electromagnetic exciter is adopted to directly obtain the magnitude of the excitation load by a force sensor mounted on the excitation rod. Particular attention is paid to the influence of the contact status of the contact surfaces, e.g. the pressure-sensitive paper is used to measure the effective contact area of the UPDs. The experimental variables are selected as the centrifugal force, the amplitude of the excitation force, the damper mass, the effective contact area, and the damper material. The Frequency Response Function(FRF) of the blade under different experimental parameters is obtained by slow frequency sweep under sinusoidal excitation to study the influence of each parameter on the dynamic characteristics of the blade and the mechanism analysis is carried out combined with the experimental results.
