The mound-making behavior of plateau zokors is one of the most important factors in remodeling meadow microtopography and causing soil erosion in the Yellow River source area of western China,but little is known about...The mound-making behavior of plateau zokors is one of the most important factors in remodeling meadow microtopography and causing soil erosion in the Yellow River source area of western China,but little is known about the effects of microtopography on particle size characteristics(PSC)of eroded sediments from the bare slopes of zokor mounds during different rainfall events.In this study,we analyzed the relationship of microtopographic features derived from laser point cloud data and PSC of eroded sediments at six simulated rainfall intensities(all lasting 60 min).The effects of microtopography on PSC of eroded sediments were studied via partial least squares regression(PLSR)and structural equation modeling(SEM).The results showed that:(1)15-20 minutes from the beginning of rainfall was the sensitive period of soil loss from the slopes,and the function relationship between the rate of sediment and runoff and rainfall intensity can better predict the development trend of soil erosion;(2)Intense erosion occurred mainly in the upper half of the zokor mound,while deposition was mainly limited to its lower half.It is suggested that diminished plateau zokor activity intensity can effectively prevent and control soil erosion;(3)The PSC of eroded sediment is dominated by silt,followed by sand,with clay being the least abundant,and the eroded sediments with a particle size of 10-20μm were sensitive and highly susceptible to rainfall erosion.This finding facilitates the understanding of the formation process of surface geomorphology and the mechanism of soil erosion;(4)The PLSR model indicates that microtopography has an extensive influence on eroded sediments during hydraulic erosion,and the SEM analysis results further confirm that the fractal dimension was the best parameter to represent the PSC of eroded sediments,whereas surface cutting degree was the dominant factor controlling the PSC of eroded sediments.These findings are crucial for predicting soil erosion in the Yellow River source area and provide a new perspective for understanding soil erosion mechanisms in alpine meadow ecosystems.展开更多
To determine the root cause of a bare-spot defect in a hot-dip galvanized boron-added steel sheet,we performed metallurgical characterizations using time-of-flight secondary ion mass spectrometry(ToF-SIMS)in addition ...To determine the root cause of a bare-spot defect in a hot-dip galvanized boron-added steel sheet,we performed metallurgical characterizations using time-of-flight secondary ion mass spectrometry(ToF-SIMS)in addition to glow discharge optical emission spectrometry,field-emission scanning electron microscopy(FE-SEM),and energy dispersive spectroscopy.Mn and B enrichments on the steel surface in the bare-spot area were detected through various methods.FE-SEM revealed external oxide nodules and zinc droplets,which indicated poor wettability.ToF-SIMS further revealed considerably more detailed lateral and depth distributions of Mn,B,and Al.The formation of external Mn-B compound oxides on the steel surface prior to hot dipping,which substantially deteriorated the wettability and prevented the formation of a Fe_(2)Al_(5)inhibition layer,resulted in the formation of a bare-spot defect.ToF-SIMS mapping of Al ion proved that a slight reaction still occurred between the dissolved Al in the molten zinc bath and steel substrate,although no evident Fe_(2)Al_(5)inhibition layer formed in the bare-spot area.展开更多
Microlysimeters of different sizes(5 cm 10 cm and 15 cm in length)were used extensively in the present study for the measurements of soil evapondion in site in an extremely arid area in southern Israel.All of the data...Microlysimeters of different sizes(5 cm 10 cm and 15 cm in length)were used extensively in the present study for the measurements of soil evapondion in site in an extremely arid area in southern Israel.All of the data obtained from the microlysimeters were used to evaluate two conventional eVaporation models developed by Black et al.and Ritchie,respectively.Our results indicated that the models could overestimate total cumulative evaporation by about 30% in the extremely arid environment.Reducing the power factor of the conventional model by a faCtor of 0.1 produced good agreement between the measured and simulated cumulative evaporation.Microlysimeter method proved to be a simple and accurate approach for the evaluation of soil evaporstion.展开更多
Understanding the impact of rock bareness on the transpiration in karst plants is essential to karst rocky desertification control and sustainable management of plantation in karst area.This study focused on the varia...Understanding the impact of rock bareness on the transpiration in karst plants is essential to karst rocky desertification control and sustainable management of plantation in karst area.This study focused on the variations in sap flow of Zenia insignis caused by different rock bareness rate,and the impact of climate factors,soil water content(SWC)and leaf area index(LAI) on transpiration in karst plants,by continuously measuring sap flux densities (Fcd)of 12 sample trees using thermal dissipation probes and monitoring micrometeorology and SwC on a typical karst hill in north Guangdong of China during the year of 2016.Results show that:(1)the maximum hourly sap flux density occurred at11:00-14:00 and the peak daily sap flux density occurred in September.(2)Sap flow density of Zenia insignis increased with rock bareness rate at all hourly,daily and monthly scales,with the sequence of extremely severe>severe>moderate>mild rock bareness.(3)The transpiration of Zenia insi.gnis is controlled by different factors at different temporalscales.At hourly scale,transpiration was highly(n=144,R^2>0.72)correlated to Solar radiation(Rs),Air temperature(Ta),relative humidity(RH),and water vapor pressure deficit(VPD).At daily scale,transpiration was greatly(n=366,R2>0.31)affected by Solar radiation(Rs),Air temperature(Ta),and water vapor pressure deficit (VPD).While at monthly scale,transpiration was mainly(n=12,R^2=0.85)controlled by LAI.Our study proved that Zenia insi.gnis has a good physiecological adaption to fragile karst environment,and Zenia insignis plantation has long-term sustainability even in extremely rocky landscapes.The results may provide scientific basis for plantation management and ecological restoration in karst area.展开更多
The dynamics of soil seed banks and seed movement was investigated in three bare alkali-saline patches in Songnen grassland, Northeast China, for exploring their potential role in the vegetation restoration of bare al...The dynamics of soil seed banks and seed movement was investigated in three bare alkali-saline patches in Songnen grassland, Northeast China, for exploring their potential role in the vegetation restoration of bare alkali-saline patches. The results showed that the seed banks and the seed movement in these patches were very similar to each other, and to some extent the seed movement was related to patch-side vegetation there. Seed movement across the soil surface of these bare alkali-saline patches was abundant and dominated by the seeds of pioneer species, such as Chloris virgata and Suaeda corniculata, which accounted for over 96% of these trapped seeds. In the contrast, soil seed banks of bare patches were extremely small, in different seasons, especially in May and June, even no any seed have been found, mainly due to lowest retaining capacity of surface soil to those abundant seed movement. Both soil seed banks and seed movement showed seasonal variation, and usually reached the maximum in October. Soil seed banks of bare alkali-saline patches, which were extremely small and difficult to recruit naturally, may inhibit speed of vegetation restoration. It is suggested that seed movement would be the potential seed source and play a potentially important role in the process of vegetation restoration of bare alkali-saline patches by enhancing the soft retaining capacity to seed movement.展开更多
Complete bearing spiral case has not been applied to large power stations in China so far. The proposal of applying complete bearing spiral case necessitates an analysis of the reliability of the spiral case structure...Complete bearing spiral case has not been applied to large power stations in China so far. The proposal of applying complete bearing spiral case necessitates an analysis of the reliability of the spiral case structure and the security of units under various working conditions. In combination with practice of a project, this paper presents a three-dimensional nonlinear finite element static analysis of the concrete using a concrete smeared crack model by means of the well-known finite element method （FEM） software ABAQUS. The stress distribution of the spiral case and reinforcing bars, the range of damages in surrounding concrete, and the displacement of structure are quantified. The computational results indicate that the embedment method ensures the structure＇s safety in strength. At the same time, the result shows that this embedment is a kind of preponderant method for embedment in aspects of economy and technique of construction, and the application of this embedment method to the hydropower station is feasible provided that some proper engineering measures are taken to constrain the width of the concrete in accord with the code＇s requirements. The paper proves the security and reliability of the structural design of spiral case in hydropower station accordingly.展开更多
Munitions contain casings that consume explosive energy.The blast load(e.g.,peak overpressure and maximum impulse)intensity generated by ammunition explosion will be lower than that generated by a bare charge with equ...Munitions contain casings that consume explosive energy.The blast load(e.g.,peak overpressure and maximum impulse)intensity generated by ammunition explosion will be lower than that generated by a bare charge with equal mass.To evaluate the blast load of a cased charge under different conditions,the equivalent bare mass needs to be calculated.However,the accuracy of existing correlations strongly depends on the empirical determination of relevant controlling parameters and lacks theoretical clarification.In this paper,new correlations are proposed based on a more rigorous theoretical derivation,considering both the mechanical behaviors of the casing’s material and the change of the polytropic exponent during the expansion process of the explosion products.The controlling parameters are attributed to the rupture radius ratio and the polytropic exponent of detonation products expansion to casing rupture state.The reasonability is validated by both comprehensive numerical simulations with dynamic mechanical constitutive model and theoretical derivations.The results calculated by the new correlation show better agreement with the experimental results than those calculated by previous correlations,and the results difference is explained in more consistency with the thermos-physical properties of the charge and mechanical behaviors of casing material.Furthermore,the correlation of the cased-to-bare impulse ratio is also theoretically improved,providing a more accurate theoretical basis for both the equivalent bare mass and impulse evaluation for a cased charge.展开更多
When the soil condition and depth to water table stay constant, climate condition will then be the only determinant of evaporation intensity of phreatic water from bare soil. Based on a series of long-term quality-con...When the soil condition and depth to water table stay constant, climate condition will then be the only determinant of evaporation intensity of phreatic water from bare soil. Based on a series of long-term quality-controlled data collected at the Wudaogou Hydrological Experiment Station in the Huaibei Plain, Anhui, China, the variation trends of the evaporation rate of phreatic water from bare soil were studied through the Mann-Kendall trend test and the linear regression trend test, followed by the study on the responses of evaporation to climate change. Results indicated that in the Huaibei Plain during 1991-2008, evaporation of phreatic water from bare soil tended to increase at a rate of 5% on monthly scale in March, June and July while in other months the increase was minor. On the seasonal basis, the evaporation saw significant increase in spring and summer. In addition, annual evaporation tended to grow evidently over time. When air temperature rises by 1 °C, the annual evaporation rate increases by 7.24–14.21%, while when the vapor pressure deficit rises by 10%, it changes from-0.09 to 5.40%. The study also provides references for further understanding of the trends and responses of regional evapotranspiration to climate change.展开更多
Objectives To evaluate the very long-term safety and effectiveness of drug-eluting stents （DES） compared to bare-metal stents （BMS） for patients with large coronary vessels. Methods From April 2004 to October 2006...Objectives To evaluate the very long-term safety and effectiveness of drug-eluting stents （DES） compared to bare-metal stents （BMS） for patients with large coronary vessels. Methods From April 2004 to October 2006, 2407 consecutive patients undergoing de novo lesion percutaneous coronary intervention with reference vessel diameter greater than or equal to 3.5 mm at Fu Wai Hospital in Beijing, China, were prospectively enrolled into this study. We obtained 9-year clinical outcomes including death, myocardial infarction （MI）, thrombosis, target lesion revascularization （TLR）, target vessel revascularization （TVR）, and major adverse cardiac events （MACE, the composite of death, MI, and TVR）. We performed Cox＇s proportional-hazards models to assess relative risks of all the outcome measures after propensity match. Results After propensity scoring, 514 DES-treated patients were matched to 514 BMS-treated patients. The patients treated with BMS were associated with higher risk ofTLR （HR： 2.55, 95%CI： 1.520-4.277, P = 0.0004） and TVR （HR： 1.889, 95%CI： 1.185-3.011, P = 0.0075）, but the rates of death/MI and MACE were not statistically different. All Academic Research Consortium definition stent thrombosis at 9-year were comparable in the two groups. Conclusions During long-term follow-up through nine years, use of DES in patients with large coronary arteries was still associated with significant reductions in the risks of TLR and TVR.展开更多
The Salp Swarm Algorithm(SSA)may have trouble in dropping into stagnation as a kind of swarm intelligence method.This paper developed an adaptive barebones salp swarm algorithm with quasi-oppositional-based learning t...The Salp Swarm Algorithm(SSA)may have trouble in dropping into stagnation as a kind of swarm intelligence method.This paper developed an adaptive barebones salp swarm algorithm with quasi-oppositional-based learning to compensate for the above weakness called QBSSA.In the proposed QBSSA,an adaptive barebones strategy can help to reach both accurate convergence speed and high solution quality;quasi-oppositional-based learning can make the population away from traping into local optimal and expand the search space.To estimate the performance of the presented method,a series of tests are performed.Firstly,CEC 2017 benchmark test suit is used to test the ability to solve the high dimensional and multimodal problems;then,based on QBSSA,an improved Kernel Extreme Learning Machine(KELM)model,named QBSSA–KELM,is built to handle medical disease diagnosis problems.All the test results and discussions state clearly that the QBSSA is superior to and very competitive to all the compared algorithms on both convergence speed and solutions accuracy.展开更多
A precise detection of the fault feature parameter of motor current is a new research hotspot in the broken rotor bar(BRB) fault diagnosis of induction motors. Discrete Fourier transform(DFT) is the most popular techn...A precise detection of the fault feature parameter of motor current is a new research hotspot in the broken rotor bar(BRB) fault diagnosis of induction motors. Discrete Fourier transform(DFT) is the most popular technique in this field, owing to low computation and easy realization. However, its accuracy is often limited by the data window length, spectral leakage, fence e ect, etc. Therefore, a new detection method based on a global optimization algorithm is proposed. First, a BRB fault current model and a residual error function are designed to transform the fault parameter detection problem into a nonlinear least-square problem. Because this optimization problem has a great number of local optima and needs to be resolved rapidly and accurately, a joint algorithm(called TR-MBPSO) based on a modified bare-bones particle swarm optimization(BPSO) and trust region(TR) is subsequently proposed. In the TR-MBPSO, a reinitialization strategy of inactive particle is introduced to the BPSO to enhance the swarm diversity and global search ability. Meanwhile, the TR is combined with the modified BPSO to improve convergence speed and accuracy. It also includes a global convergence analysis, whose result proves that the TR-MBPSO can converge to the global optimum with the probability of 1. Both simulations and experiments are conducted, and the results indicate that the proposed detection method not only has high accuracy of parameter estimation with short-time data window, e.g., the magnitude and frequency precision of the fault-related components reaches 10^(-4), but also overcomes the impacts of spectral leakage and non-integer-period sampling. The proposed research provides a new BRB detection method, which has enough precision to extract the parameters of the fault feature components.展开更多
BACKGROUND A transjugular intrahepatic portosystemic shunt(TIPS)is widely placed to treat portal hypertension.Because the Viatorr®stent(W.L.Gore and Associates,Flagstaff,AZ,United States)is not available in all h...BACKGROUND A transjugular intrahepatic portosystemic shunt(TIPS)is widely placed to treat portal hypertension.Because the Viatorr®stent(W.L.Gore and Associates,Flagstaff,AZ,United States)is not available in all hospitals in China,the bare metal stent(BMS)/stent-graft combination technique is still popular for TIPS construction.Stent fracture is a complication after TIPS placement using this technique,with limited available literature focusing on it.AIM To assess the incidence of stent fracture after TIPS placement using the BMS/stent-graft combination technique and to identify the risk factors for stent fracture.We proposed technique modifications to improve the clinical results of TIPS placement with the BMS/stent-graft combination technique.METHODS We retrospectively analyzed the computed tomography(CT)data of all patients with portal hypertension who underwent the TIPS procedure between June 2011 and December 2021 in a single center.Patients implanted with the BMS/stent graft and had follow-up imaging data available were included.We identified patients with stent fracture and analyzed their characteristics.Multivariable logistic regression was applied to identify the potential predictors of stent fracture.RESULTS Of the 68 included patients,stent fracture occurred in seven(10.3%)patients.Based on CT images,the stent fractures were categorized into three types.Our study consisted of four(57.1%)type I fractures,one(14.3%)type II fracture,one(14.3%)type IIIa fracture,and one(14.3%)type IIIb fracture.After adjusting for covariates,multivariable logistic regression revealed that the risk factors for stent fracture were the implantation of a greater number of stents[adjusted odds ratio(aOR)=22.2,95%confidence interval(CI):1.2-415.4,P=0.038]and a larger proximal sagittal stent bending angle(aOR=1.1,95%CI:1.0-1.3,P=0.020).CONCLUSION Stent fracture occurred in approximately 10%of patients with portal hypertension who underwent TIPS with the BMS/stent-graft combination technique.The number of implanted stents and stent bending angle at the inferior vena cava end were predictors of stent fracture,which suggests that the incidence of stent fracture could potentially be reduced by procedural modifications.展开更多
Based on ASTER （Advanced Spaceborne Thermal Emission and Reflection Radiometer） remote sensing data, bare soil evaporation was estimated with the Penman-Monteith model, the Priestley-Taylor model, and the aerodynami...Based on ASTER （Advanced Spaceborne Thermal Emission and Reflection Radiometer） remote sensing data, bare soil evaporation was estimated with the Penman-Monteith model, the Priestley-Taylor model, and the aerodynamics model. Evaporation estimated by each of the three models was compared with actual evaporation, and error sources of the three models were analyzed. The mean absolute relative error was 9% for the Penman-Monteith model, 14% for the Priestley-Taylor model, and 32% for the aerodynamics model; the Penman-Monteith model was the best of these three models for estimating bare soil evaporation. The error source of the Penman-Monteith model is the neglect of the advection estimation. The error source of the Priestley-Taylor model is the simplification of the component of aerodynamics as 0.72 times the net radiation. The error source of the aerodynamics model is the difference of vapor pressure and neglect of the radiometric component. The spatial distribution of bare soil evaporation is evident, and its main factors are soil water content and elevation.展开更多
In this paper, the formula for calculating the power consumption of a bare spindle(without bobbin) is introduced, which is suitable to all spindle of similar structure. The results of calculation for D1203 spindle agr...In this paper, the formula for calculating the power consumption of a bare spindle(without bobbin) is introduced, which is suitable to all spindle of similar structure. The results of calculation for D1203 spindle agrees closely with the results of measurement. The calculated results show that power is consumed by three main parts, and mostly by the part of spindle upper bearing. The way of reducing power consumption of bare spindle is also recommended in the paper.展开更多
Several bare zigzag phosphorene nanoribbons with odd number of atoms in the direction perpendicular to the extended line are investigated by using HSE06 density functional theory.These nanoribbons are as stable as tho...Several bare zigzag phosphorene nanoribbons with odd number of atoms in the direction perpendicular to the extended line are investigated by using HSE06 density functional theory.These nanoribbons are as stable as those with even number of atoms.Primitive cells of the nanoribbons are metals,while edge self-passivation and distortion in the supercell structures cause metal-semiconductor transition.The band gaps of semiconducting nanoribbons are around 0.4 eV,which is enough for high on/off ratio in device operation.Compared to the conduction bands,the valence bands have smaller deformation potential constants and larger band width.Thus,the hole mobilities of the nanoribbons（10 cm^2·V^（-1）·s^（-1）） are one order higher than the electron mobilities.Bare zigzag phosphorene nanoribbons with odd number of atoms can also be candidates for small-size high-speed electronic devices.展开更多
Soil moisture is an important parameter for agriculture, meteorological, and hydrological studies. This paper focuses on soil-moisture estimation methodology based on the multi-angle high-and low-incidence-angle mode ...Soil moisture is an important parameter for agriculture, meteorological, and hydrological studies. This paper focuses on soil-moisture estimation methodology based on the multi-angle high-and low-incidence-angle mode RADARSAT-2 data obtained over bare agricultural fields in an arid area. Backscattering of the high-and low-incidence angles is simulated by using AIEM(advanced integral equation model), with the surface-roughness estimation model built based on the simulated data. Combining the surface-roughness estimation model with the backscattering model of the low-incidence-angle mode, a soil-moisture estimation method is put forward. First, the natural logarithm(ln) of soil moisture was obtained and then the soil moisture calculated. Soil moisture of the study area in Dunhuang, Gansu Province, was obtained based on this method; a good agreement was observed between the estimated and measured soil moisture. The coefficient of determination was 0.85, and the estimation precision reached 4.02% in root mean square error(RMSE). The results illustrate the high potential of the approach developed and RADARSAT-2 data to monitor soil moisture.展开更多
基金financially supported by the Qinghai University Graduate Student Research and Practice Innovation Project(2025-GPKY-12)Basic Research Project of Qinghai Provincial Science and Technology Department(2021-ZJ-701)+1 种基金National Natural Science Foundation of China(U23A20159,42161068)the 111 Project of China(D18013)。
文摘The mound-making behavior of plateau zokors is one of the most important factors in remodeling meadow microtopography and causing soil erosion in the Yellow River source area of western China,but little is known about the effects of microtopography on particle size characteristics(PSC)of eroded sediments from the bare slopes of zokor mounds during different rainfall events.In this study,we analyzed the relationship of microtopographic features derived from laser point cloud data and PSC of eroded sediments at six simulated rainfall intensities(all lasting 60 min).The effects of microtopography on PSC of eroded sediments were studied via partial least squares regression(PLSR)and structural equation modeling(SEM).The results showed that:(1)15-20 minutes from the beginning of rainfall was the sensitive period of soil loss from the slopes,and the function relationship between the rate of sediment and runoff and rainfall intensity can better predict the development trend of soil erosion;(2)Intense erosion occurred mainly in the upper half of the zokor mound,while deposition was mainly limited to its lower half.It is suggested that diminished plateau zokor activity intensity can effectively prevent and control soil erosion;(3)The PSC of eroded sediment is dominated by silt,followed by sand,with clay being the least abundant,and the eroded sediments with a particle size of 10-20μm were sensitive and highly susceptible to rainfall erosion.This finding facilitates the understanding of the formation process of surface geomorphology and the mechanism of soil erosion;(4)The PLSR model indicates that microtopography has an extensive influence on eroded sediments during hydraulic erosion,and the SEM analysis results further confirm that the fractal dimension was the best parameter to represent the PSC of eroded sediments,whereas surface cutting degree was the dominant factor controlling the PSC of eroded sediments.These findings are crucial for predicting soil erosion in the Yellow River source area and provide a new perspective for understanding soil erosion mechanisms in alpine meadow ecosystems.
文摘To determine the root cause of a bare-spot defect in a hot-dip galvanized boron-added steel sheet,we performed metallurgical characterizations using time-of-flight secondary ion mass spectrometry(ToF-SIMS)in addition to glow discharge optical emission spectrometry,field-emission scanning electron microscopy(FE-SEM),and energy dispersive spectroscopy.Mn and B enrichments on the steel surface in the bare-spot area were detected through various methods.FE-SEM revealed external oxide nodules and zinc droplets,which indicated poor wettability.ToF-SIMS further revealed considerably more detailed lateral and depth distributions of Mn,B,and Al.The formation of external Mn-B compound oxides on the steel surface prior to hot dipping,which substantially deteriorated the wettability and prevented the formation of a Fe_(2)Al_(5)inhibition layer,resulted in the formation of a bare-spot defect.ToF-SIMS mapping of Al ion proved that a slight reaction still occurred between the dissolved Al in the molten zinc bath and steel substrate,although no evident Fe_(2)Al_(5)inhibition layer formed in the bare-spot area.
文摘Microlysimeters of different sizes(5 cm 10 cm and 15 cm in length)were used extensively in the present study for the measurements of soil evapondion in site in an extremely arid area in southern Israel.All of the data obtained from the microlysimeters were used to evaluate two conventional eVaporation models developed by Black et al.and Ritchie,respectively.Our results indicated that the models could overestimate total cumulative evaporation by about 30% in the extremely arid environment.Reducing the power factor of the conventional model by a faCtor of 0.1 produced good agreement between the measured and simulated cumulative evaporation.Microlysimeter method proved to be a simple and accurate approach for the evaluation of soil evaporstion.
基金supported by the project of the National Natural Science Foundation of China entitled ‘‘Impact of rocky desertification on stand transpiration of Zenia insignis plantation and the mechanism’’ (No. 41401108)the project of the National Natural Science Foundation of China entitled ‘‘The impact of development of soil cracks in collapsed walls on wall collapsing stability in granite red soil region of south China’’ (No. 41371041)
文摘Understanding the impact of rock bareness on the transpiration in karst plants is essential to karst rocky desertification control and sustainable management of plantation in karst area.This study focused on the variations in sap flow of Zenia insignis caused by different rock bareness rate,and the impact of climate factors,soil water content(SWC)and leaf area index(LAI) on transpiration in karst plants,by continuously measuring sap flux densities (Fcd)of 12 sample trees using thermal dissipation probes and monitoring micrometeorology and SwC on a typical karst hill in north Guangdong of China during the year of 2016.Results show that:(1)the maximum hourly sap flux density occurred at11:00-14:00 and the peak daily sap flux density occurred in September.(2)Sap flow density of Zenia insignis increased with rock bareness rate at all hourly,daily and monthly scales,with the sequence of extremely severe>severe>moderate>mild rock bareness.(3)The transpiration of Zenia insi.gnis is controlled by different factors at different temporalscales.At hourly scale,transpiration was highly(n=144,R^2>0.72)correlated to Solar radiation(Rs),Air temperature(Ta),relative humidity(RH),and water vapor pressure deficit(VPD).At daily scale,transpiration was greatly(n=366,R2>0.31)affected by Solar radiation(Rs),Air temperature(Ta),and water vapor pressure deficit (VPD).While at monthly scale,transpiration was mainly(n=12,R^2=0.85)controlled by LAI.Our study proved that Zenia insi.gnis has a good physiecological adaption to fragile karst environment,and Zenia insignis plantation has long-term sustainability even in extremely rocky landscapes.The results may provide scientific basis for plantation management and ecological restoration in karst area.
基金The study was supported by the State Basic Research and Development Plan of China (G2000018602)
文摘The dynamics of soil seed banks and seed movement was investigated in three bare alkali-saline patches in Songnen grassland, Northeast China, for exploring their potential role in the vegetation restoration of bare alkali-saline patches. The results showed that the seed banks and the seed movement in these patches were very similar to each other, and to some extent the seed movement was related to patch-side vegetation there. Seed movement across the soil surface of these bare alkali-saline patches was abundant and dominated by the seeds of pioneer species, such as Chloris virgata and Suaeda corniculata, which accounted for over 96% of these trapped seeds. In the contrast, soil seed banks of bare patches were extremely small, in different seasons, especially in May and June, even no any seed have been found, mainly due to lowest retaining capacity of surface soil to those abundant seed movement. Both soil seed banks and seed movement showed seasonal variation, and usually reached the maximum in October. Soil seed banks of bare alkali-saline patches, which were extremely small and difficult to recruit naturally, may inhibit speed of vegetation restoration. It is suggested that seed movement would be the potential seed source and play a potentially important role in the process of vegetation restoration of bare alkali-saline patches by enhancing the soft retaining capacity to seed movement.
基金Supported by the Sustentation Plan Projects for Out-standing Young Teachers of the Ministry of Education (20011879)
文摘Complete bearing spiral case has not been applied to large power stations in China so far. The proposal of applying complete bearing spiral case necessitates an analysis of the reliability of the spiral case structure and the security of units under various working conditions. In combination with practice of a project, this paper presents a three-dimensional nonlinear finite element static analysis of the concrete using a concrete smeared crack model by means of the well-known finite element method （FEM） software ABAQUS. The stress distribution of the spiral case and reinforcing bars, the range of damages in surrounding concrete, and the displacement of structure are quantified. The computational results indicate that the embedment method ensures the structure＇s safety in strength. At the same time, the result shows that this embedment is a kind of preponderant method for embedment in aspects of economy and technique of construction, and the application of this embedment method to the hydropower station is feasible provided that some proper engineering measures are taken to constrain the width of the concrete in accord with the code＇s requirements. The paper proves the security and reliability of the structural design of spiral case in hydropower station accordingly.
文摘Munitions contain casings that consume explosive energy.The blast load(e.g.,peak overpressure and maximum impulse)intensity generated by ammunition explosion will be lower than that generated by a bare charge with equal mass.To evaluate the blast load of a cased charge under different conditions,the equivalent bare mass needs to be calculated.However,the accuracy of existing correlations strongly depends on the empirical determination of relevant controlling parameters and lacks theoretical clarification.In this paper,new correlations are proposed based on a more rigorous theoretical derivation,considering both the mechanical behaviors of the casing’s material and the change of the polytropic exponent during the expansion process of the explosion products.The controlling parameters are attributed to the rupture radius ratio and the polytropic exponent of detonation products expansion to casing rupture state.The reasonability is validated by both comprehensive numerical simulations with dynamic mechanical constitutive model and theoretical derivations.The results calculated by the new correlation show better agreement with the experimental results than those calculated by previous correlations,and the results difference is explained in more consistency with the thermos-physical properties of the charge and mechanical behaviors of casing material.Furthermore,the correlation of the cased-to-bare impulse ratio is also theoretically improved,providing a more accurate theoretical basis for both the equivalent bare mass and impulse evaluation for a cased charge.
基金financially supported by“the Fundamental Research Funds for the Central Universities”of Hefei University of Technology(No.JZ2014HGBZ0040)the National Natural Science Foundation of China(No.51509064+2 种基金No.51309071No.51309155)the National Key Research and Development Programs of China(Grand 2016YFA0601601,2016YFA0601501)
文摘When the soil condition and depth to water table stay constant, climate condition will then be the only determinant of evaporation intensity of phreatic water from bare soil. Based on a series of long-term quality-controlled data collected at the Wudaogou Hydrological Experiment Station in the Huaibei Plain, Anhui, China, the variation trends of the evaporation rate of phreatic water from bare soil were studied through the Mann-Kendall trend test and the linear regression trend test, followed by the study on the responses of evaporation to climate change. Results indicated that in the Huaibei Plain during 1991-2008, evaporation of phreatic water from bare soil tended to increase at a rate of 5% on monthly scale in March, June and July while in other months the increase was minor. On the seasonal basis, the evaporation saw significant increase in spring and summer. In addition, annual evaporation tended to grow evidently over time. When air temperature rises by 1 °C, the annual evaporation rate increases by 7.24–14.21%, while when the vapor pressure deficit rises by 10%, it changes from-0.09 to 5.40%. The study also provides references for further understanding of the trends and responses of regional evapotranspiration to climate change.
文摘Objectives To evaluate the very long-term safety and effectiveness of drug-eluting stents （DES） compared to bare-metal stents （BMS） for patients with large coronary vessels. Methods From April 2004 to October 2006, 2407 consecutive patients undergoing de novo lesion percutaneous coronary intervention with reference vessel diameter greater than or equal to 3.5 mm at Fu Wai Hospital in Beijing, China, were prospectively enrolled into this study. We obtained 9-year clinical outcomes including death, myocardial infarction （MI）, thrombosis, target lesion revascularization （TLR）, target vessel revascularization （TVR）, and major adverse cardiac events （MACE, the composite of death, MI, and TVR）. We performed Cox＇s proportional-hazards models to assess relative risks of all the outcome measures after propensity match. Results After propensity scoring, 514 DES-treated patients were matched to 514 BMS-treated patients. The patients treated with BMS were associated with higher risk ofTLR （HR： 2.55, 95%CI： 1.520-4.277, P = 0.0004） and TVR （HR： 1.889, 95%CI： 1.185-3.011, P = 0.0075）, but the rates of death/MI and MACE were not statistically different. All Academic Research Consortium definition stent thrombosis at 9-year were comparable in the two groups. Conclusions During long-term follow-up through nine years, use of DES in patients with large coronary arteries was still associated with significant reductions in the risks of TLR and TVR.
基金supported by the National Natural Science Foundation of China(62076185,U1809209)supported by Zhejiang Provincial Natural Science Foundation of China(LY21F020030)+1 种基金Wenzhou Major Scientific and Technological Innovation Project(ZY2019019)Wenzhou Science and Technology Bureau(2018ZG016)。
文摘The Salp Swarm Algorithm(SSA)may have trouble in dropping into stagnation as a kind of swarm intelligence method.This paper developed an adaptive barebones salp swarm algorithm with quasi-oppositional-based learning to compensate for the above weakness called QBSSA.In the proposed QBSSA,an adaptive barebones strategy can help to reach both accurate convergence speed and high solution quality;quasi-oppositional-based learning can make the population away from traping into local optimal and expand the search space.To estimate the performance of the presented method,a series of tests are performed.Firstly,CEC 2017 benchmark test suit is used to test the ability to solve the high dimensional and multimodal problems;then,based on QBSSA,an improved Kernel Extreme Learning Machine(KELM)model,named QBSSA–KELM,is built to handle medical disease diagnosis problems.All the test results and discussions state clearly that the QBSSA is superior to and very competitive to all the compared algorithms on both convergence speed and solutions accuracy.
基金Supported by Fundamental Research Funds for the Central Universities(Grant No.2017XKQY032)
文摘A precise detection of the fault feature parameter of motor current is a new research hotspot in the broken rotor bar(BRB) fault diagnosis of induction motors. Discrete Fourier transform(DFT) is the most popular technique in this field, owing to low computation and easy realization. However, its accuracy is often limited by the data window length, spectral leakage, fence e ect, etc. Therefore, a new detection method based on a global optimization algorithm is proposed. First, a BRB fault current model and a residual error function are designed to transform the fault parameter detection problem into a nonlinear least-square problem. Because this optimization problem has a great number of local optima and needs to be resolved rapidly and accurately, a joint algorithm(called TR-MBPSO) based on a modified bare-bones particle swarm optimization(BPSO) and trust region(TR) is subsequently proposed. In the TR-MBPSO, a reinitialization strategy of inactive particle is introduced to the BPSO to enhance the swarm diversity and global search ability. Meanwhile, the TR is combined with the modified BPSO to improve convergence speed and accuracy. It also includes a global convergence analysis, whose result proves that the TR-MBPSO can converge to the global optimum with the probability of 1. Both simulations and experiments are conducted, and the results indicate that the proposed detection method not only has high accuracy of parameter estimation with short-time data window, e.g., the magnitude and frequency precision of the fault-related components reaches 10^(-4), but also overcomes the impacts of spectral leakage and non-integer-period sampling. The proposed research provides a new BRB detection method, which has enough precision to extract the parameters of the fault feature components.
文摘BACKGROUND A transjugular intrahepatic portosystemic shunt(TIPS)is widely placed to treat portal hypertension.Because the Viatorr®stent(W.L.Gore and Associates,Flagstaff,AZ,United States)is not available in all hospitals in China,the bare metal stent(BMS)/stent-graft combination technique is still popular for TIPS construction.Stent fracture is a complication after TIPS placement using this technique,with limited available literature focusing on it.AIM To assess the incidence of stent fracture after TIPS placement using the BMS/stent-graft combination technique and to identify the risk factors for stent fracture.We proposed technique modifications to improve the clinical results of TIPS placement with the BMS/stent-graft combination technique.METHODS We retrospectively analyzed the computed tomography(CT)data of all patients with portal hypertension who underwent the TIPS procedure between June 2011 and December 2021 in a single center.Patients implanted with the BMS/stent graft and had follow-up imaging data available were included.We identified patients with stent fracture and analyzed their characteristics.Multivariable logistic regression was applied to identify the potential predictors of stent fracture.RESULTS Of the 68 included patients,stent fracture occurred in seven(10.3%)patients.Based on CT images,the stent fractures were categorized into three types.Our study consisted of four(57.1%)type I fractures,one(14.3%)type II fracture,one(14.3%)type IIIa fracture,and one(14.3%)type IIIb fracture.After adjusting for covariates,multivariable logistic regression revealed that the risk factors for stent fracture were the implantation of a greater number of stents[adjusted odds ratio(aOR)=22.2,95%confidence interval(CI):1.2-415.4,P=0.038]and a larger proximal sagittal stent bending angle(aOR=1.1,95%CI:1.0-1.3,P=0.020).CONCLUSION Stent fracture occurred in approximately 10%of patients with portal hypertension who underwent TIPS with the BMS/stent-graft combination technique.The number of implanted stents and stent bending angle at the inferior vena cava end were predictors of stent fracture,which suggests that the incidence of stent fracture could potentially be reduced by procedural modifications.
基金supported by the Ministry of Water Resources (Grants No. 200701039 and 200801001)the National Technology Supporting Program (Grants No. 2006BAC05B02 and 2007BAC03A060301)
文摘Based on ASTER （Advanced Spaceborne Thermal Emission and Reflection Radiometer） remote sensing data, bare soil evaporation was estimated with the Penman-Monteith model, the Priestley-Taylor model, and the aerodynamics model. Evaporation estimated by each of the three models was compared with actual evaporation, and error sources of the three models were analyzed. The mean absolute relative error was 9% for the Penman-Monteith model, 14% for the Priestley-Taylor model, and 32% for the aerodynamics model; the Penman-Monteith model was the best of these three models for estimating bare soil evaporation. The error source of the Penman-Monteith model is the neglect of the advection estimation. The error source of the Priestley-Taylor model is the simplification of the component of aerodynamics as 0.72 times the net radiation. The error source of the aerodynamics model is the difference of vapor pressure and neglect of the radiometric component. The spatial distribution of bare soil evaporation is evident, and its main factors are soil water content and elevation.
文摘In this paper, the formula for calculating the power consumption of a bare spindle(without bobbin) is introduced, which is suitable to all spindle of similar structure. The results of calculation for D1203 spindle agrees closely with the results of measurement. The calculated results show that power is consumed by three main parts, and mostly by the part of spindle upper bearing. The way of reducing power consumption of bare spindle is also recommended in the paper.
基金supported by the National Natural Science Foundation of China(No.21203127)the Beijing Higher Education Young Elite Teacher Project(YETP1629)the Scientific Research Base Development Program of the Beijing Municipal Commission of Education
文摘Several bare zigzag phosphorene nanoribbons with odd number of atoms in the direction perpendicular to the extended line are investigated by using HSE06 density functional theory.These nanoribbons are as stable as those with even number of atoms.Primitive cells of the nanoribbons are metals,while edge self-passivation and distortion in the supercell structures cause metal-semiconductor transition.The band gaps of semiconducting nanoribbons are around 0.4 eV,which is enough for high on/off ratio in device operation.Compared to the conduction bands,the valence bands have smaller deformation potential constants and larger band width.Thus,the hole mobilities of the nanoribbons（10 cm^2·V^（-1）·s^（-1）） are one order higher than the electron mobilities.Bare zigzag phosphorene nanoribbons with odd number of atoms can also be candidates for small-size high-speed electronic devices.
基金supported by the National Natural Science Foundation of China(41401408 and41371027)the Opening Fund of Key Laboratory of Desert and Desertification,Chinese Academy of Sciences
文摘Soil moisture is an important parameter for agriculture, meteorological, and hydrological studies. This paper focuses on soil-moisture estimation methodology based on the multi-angle high-and low-incidence-angle mode RADARSAT-2 data obtained over bare agricultural fields in an arid area. Backscattering of the high-and low-incidence angles is simulated by using AIEM(advanced integral equation model), with the surface-roughness estimation model built based on the simulated data. Combining the surface-roughness estimation model with the backscattering model of the low-incidence-angle mode, a soil-moisture estimation method is put forward. First, the natural logarithm(ln) of soil moisture was obtained and then the soil moisture calculated. Soil moisture of the study area in Dunhuang, Gansu Province, was obtained based on this method; a good agreement was observed between the estimated and measured soil moisture. The coefficient of determination was 0.85, and the estimation precision reached 4.02% in root mean square error(RMSE). The results illustrate the high potential of the approach developed and RADARSAT-2 data to monitor soil moisture.
