A new method for the determination of effective flange width under uniform load on simply supported box girder bridges considering shear lag effect is proposed in this paper. Based on the Symplectic Elasticity method,...A new method for the determination of effective flange width under uniform load on simply supported box girder bridges considering shear lag effect is proposed in this paper. Based on the Symplectic Elasticity method, the flange slab of the box girder is simplified into a plane stress plate. Using equilibrium conditions of the plates, the Hamilton dual equations for top plate element is established. The analytical formulas of each plate element considering shear lag effect are derived. The closed polynomial effective width expression of flange slab under uniform load on the whole span length has been obtained. Through examples using the finite element method, the results obtained by the proposed method are examined and the accuracy of the proposed method is verified.展开更多
This paper presents a theoretical study of the pulse-width effects on the damage process of a typical bipolar transistor caused by high power microwaves（HPMs） through the injection approach.The dependences of the mi...This paper presents a theoretical study of the pulse-width effects on the damage process of a typical bipolar transistor caused by high power microwaves（HPMs） through the injection approach.The dependences of the microwave damage power,P,and the absorbed energy,E,required to cause the device failure on the pulse width τ are obtained in the nanosecond region by utilizing the curve fitting method.A comparison of the microwave pulse damage data and the existing dc pulse damage data for the same transistor is carried out.By means of a two-dimensional simulator,ISE-TCAD,the internal damage processes of the device caused by microwave voltage signals and dc pulse voltage signals are analyzed comparatively.The simulation results suggest that the temperature-rising positions of the device induced by the microwaves in the negative and positive half periods are different,while only one hot spot exists under the injection of dc pulses.The results demonstrate that the microwave damage power threshold and the absorbed energy must exceed the dc pulse power threshold and the absorbed energy,respectively.The dc pulse damage data may be useful as a lower bound for microwave pulse damage data.展开更多
The effect of the valence band tail width on the open circuit voltage of P3HT：PCBM bulk heterojunction solar cell is investigated by using the AMPS-1D computer program. An effective medium model with exponential vale...The effect of the valence band tail width on the open circuit voltage of P3HT：PCBM bulk heterojunction solar cell is investigated by using the AMPS-1D computer program. An effective medium model with exponential valence and conduction band tail states is used to simulate the photovoltaic cell. The simulation result shows that the open circuit voltage depends Iinearly on the logarithm of the generation rate and the slope depends on the width of the valence band tail. The open circuit voltage decreases with the increasing width of the band tail. The dark and light ideality factors increase with the width of the valence band tail.展开更多
Aerial spraying plays an important role in promoting agricultural production and protecting the biological environment due to its flexibility,high effectiveness,and large operational area per unit of time.In order to ...Aerial spraying plays an important role in promoting agricultural production and protecting the biological environment due to its flexibility,high effectiveness,and large operational area per unit of time.In order to evaluate the performance parameters of the spraying systems on two fixed wing airplanes M-18B and Thrush 510G,the effective swath width and uniformity of droplet deposition under headwind flight were tested while the planes operated at the altitudes of 5 m and 4 m.The results showed that although wind velocities varied from 0.9 m/s to 4.6 m/s,and the directions of the atomizer switched upward and downward in eight flights,the effective swath widths were kept approximately at 27 m and 15 m for the M-18B and Thrush 510G,respectively,and the latter was more stable.In addition,through analyzing the coefficients of variation(CVs)of droplet distribution,it was found that the CVs of the M-18B were 39.57%,33.54%,47.95%,and 59.04% at wind velocities of 0.9,1.1,1.4 and 4.6 m/s,respectively,gradually enhancing with the increasing of wind speed;the CVs of Thrush 510G were 79.12%,46.19%,14.90%,and 48.69% at wind velocities of 1.3,2.3,3.0 and 3.4 m/s,respectively,which displayed the irregularity maybe due to change of instantaneous wind direction.Moreover,in terms of the CVs and features of droplet distribution uniformity for both airplanes in the spray swath,choosing smaller CV(20%-45%)as the standard of estimation,it was found that the Thrush 510G had a better uniform droplet distribution than the M-18B.The results provide a research foundation for promoting the development of aerial spraying in China.展开更多
Based on the elastic-plastic, large-deformation finite element method, burst capacity of steel pipeline with longitudinal corrosion defect subjected to internal pressure is studied. The appropriate stress-based criter...Based on the elastic-plastic, large-deformation finite element method, burst capacity of steel pipeline with longitudinal corrosion defect subjected to internal pressure is studied. The appropriate stress-based criterion is used to predict the failure pressure of finite element model of corroded pipeline under internal pressure. By considering the pipe steel grades and geometries of corrosion defects, a series of finite element analyses is conducted. The effects of corrosion depth, length and width on burst capacity are also discussed. A specific failure pressure solution for the assessment of corrosion defects in moderate-to-high strength pipeline is proposed on the base of numerical results. The failure pressures predicted by the proposed method are in better agreement with the experimental results than the results by the other methods.展开更多
Based on the observation that both subthreshold and gate leakage depend on transistors width, this paper introduces a feasible method to fast estimate leakage current in buffers. In simulating of leakage current with ...Based on the observation that both subthreshold and gate leakage depend on transistors width, this paper introduces a feasible method to fast estimate leakage current in buffers. In simulating of leakage current with swept transistor width, we found that gate leakage is not always a linear function of the device geometry. Subsequently, this paper presented the theoretical analysis and experimental evidence of this exceptional gate leakage behavior and developed a design methodology to devise a low-leakage and high-performance buffer with no penalty in area using this deviation.展开更多
A novel slotted optical microdisk resonator, which significantly enhances light–matter interaction and provides a promising approach for increasing the sensitivity of sensors, is theoretically and numerically investi...A novel slotted optical microdisk resonator, which significantly enhances light–matter interaction and provides a promising approach for increasing the sensitivity of sensors, is theoretically and numerically investigated. In this slotted resonator, the mode splitting is generated due to reflection of the slot. Remarkably, effects of the slot width and angular position on the mode splitting are mainly studied. The results reveal that the mode splitting is a second function of the slot width, and the maximum mode splitting induced by the slot deformation is achieved with 2.7853 × 10~9Hz∕nm. Therefore, the slotted resonator is an excellent candidate for pressure and force sensing. Besides, the influence of the slot angular position on the mode splitting is a cosine curve with the highest sensitivity of 1.23 × 10^(11)Hz∕deg; thus, the optical characteristic demonstrates that the slotted resonator can be used for inertial measurements.展开更多
In steel-concrete composite twin-girder decks, wide concrete slab would undergo significant shear lag warping effect, including positive and negative. Some researchers have investigated the positive shear lag of compo...In steel-concrete composite twin-girder decks, wide concrete slab would undergo significant shear lag warping effect, including positive and negative. Some researchers have investigated the positive shear lag of composite decks by means of one-dimensional line model, while the studies on the negative shear lag have not yet been reported until now. In this study, a new one-dimensional analytical model of composite twin-girder decks is first proposed based on the model proposed by Dezi et al. Besides slab shear lag effect and partial connection at slab-girder interface which have been included in the model of Dezi et al., the particularity of the proposed model relies on its ability to account for variation characteristic of cross-section. Verification of the analytical model is later conducted through comparison of results from the analytical analysis and elaborate FE analysis for a simply supported composite deck with increasing depth and a two-span continuous one with decreasing depth. Finally, three kinds of structural forms of composite twin-girder decks, including cantilever, simply supported and continuous decks, are selected to carry out the analysis of positive and negative shear lag behaviors by means of the analytical model. The influences of cross-sectional variation characteristic and load type on positive and negative shear lag behaviors are mainly investigated. Additionally, a new definition on effective width for considering simultaneously positive and negative shear lag behaviors is proposed. The results from the proposed analytical model and EC4 specification are compared to provide suggestions for designers and checkers. In this study, the proposed analytical model can provide a powerful numerical tool for researchers to conduct the further investigation, and the analysis on shear lag and effective width can assist in design analysis of composite twin-girder decks.展开更多
This paper presents an experimental study investigating factors influencing the effective width of steel reinforced concrete (SRC) column-steel beam joints of building in order to calculate its resisting moment.Five 1...This paper presents an experimental study investigating factors influencing the effective width of steel reinforced concrete (SRC) column-steel beam joints of building in order to calculate its resisting moment.Five 1/2 scaled interior SRC column-steel beam joint specimens were made with considering parameters such as beam flange width,beam depth and SRC column width.One directional increasing moment was applied to the joint by acting forces to each ends of beam and the structural behavior of joint was studied.And previous design method suggested by Deierlein was reviewed and a modified equation was proposed from the analysis of test result.Test result indicated that the equation to calculate the effective width in Deierlein’s design method didn’t consider effectively the influence caused by the variation of beam depth so that a modified equation was suggested and the validation of it was confirmed in this paper.展开更多
The effective swath width(ESW)and the droplet penetration rate(DPR)directly affect the spraying quality,the spraying efficiency and the control effect of pests and diseases during the crop protection unmanned aircraft...The effective swath width(ESW)and the droplet penetration rate(DPR)directly affect the spraying quality,the spraying efficiency and the control effect of pests and diseases during the crop protection unmanned aircraft system(CPUAS)application.However,the ESW and DPR are not constant with the changes of the flight speed(FS)and the flight height(FH).In order to investigate the ESW and DPR of the CPUAS P20,four levels of FS(3 m/s,4 m/s,5 m/s and 6 m/s)and three levels of FH(1.5 m,2.0 m and 2.5 m)experiments were carried out according to the first industry standard of China for the CPUAS in the wheat field.The results demonstrated that the ESWs were negatively correlated with the FS and the FH.Most of the ESWs were over 2 m in the 12 treatments,in which the maximum one was 3.25 m(3 m/s,1.5 m).The DPRs were negatively correlated with the FH under the same FS,the average value of the DPRs was 48.37%,in which the maximum one was 78.34%(4 m/s,1.5 m)and the minimum one was 25.5%(6.0 m/s,2.5 m).The statistical analyses showed that the FS had significant impacts on the ESWs(0.01<p-value<0.05)while there were no significant differences among different FH treatments(p-value>0.05).The impacts of both FS and FH on the DPRs were extremely significant(p-value<0.01),and the interactive impacts were significant(0.01<p-value<0.05).Therefore,it is concluded that reducing the FS could increase the ESWs,and reducing the FH could increase the DRPs at the same FS.In conclusion,the maximum spraying efficiency of P20 was 4.342 hm2/h with 6 m/s FS and 1.5 m FH in case of satisfying the requirement of DPRs.This study provided scientific references for guiding the CPUAS spraying.展开更多
Unmanned agricultural aircraft system(UAAS)hasbeen widely employed as a low-cost and reliable method to apply agrochemicals to small agricultural fields in China.The performance of battery-poweredmultirotor UAAS has a...Unmanned agricultural aircraft system(UAAS)hasbeen widely employed as a low-cost and reliable method to apply agrochemicals to small agricultural fields in China.The performance of battery-poweredmultirotor UAAS has attracted considerable attention from manufacturers and researchers.The objective of this research was to design a UAAS equippingwith a data acquisition system,to characterize its chemical application performance based on droplet deposition data and optimize the operating parameters.Each test was repeated three times to assess the reliability of the spraying system.Various flight parameters were also evaluated.The optimal spray pressure for the XR8001 and XR8002(TeeJet,Wheaton,IL,USA)nozzles was found to be 300 kPa,and the latter nozzle had a higher droplet deposition rate and spray volume.Spray volume was not significantly affected by the flight speed or droplet density and was negatively correlated with the nozzle pressure.The results of this study provide a basis for improving the efficiency of UAAS chemicalapplication systems in terms of large-scale application.展开更多
基金supported by a grant from the Science and Technology Bureau of Jilin Province,China (No.20050531)
文摘A new method for the determination of effective flange width under uniform load on simply supported box girder bridges considering shear lag effect is proposed in this paper. Based on the Symplectic Elasticity method, the flange slab of the box girder is simplified into a plane stress plate. Using equilibrium conditions of the plates, the Hamilton dual equations for top plate element is established. The analytical formulas of each plate element considering shear lag effect are derived. The closed polynomial effective width expression of flange slab under uniform load on the whole span length has been obtained. Through examples using the finite element method, the results obtained by the proposed method are examined and the accuracy of the proposed method is verified.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60776034)
文摘This paper presents a theoretical study of the pulse-width effects on the damage process of a typical bipolar transistor caused by high power microwaves（HPMs） through the injection approach.The dependences of the microwave damage power,P,and the absorbed energy,E,required to cause the device failure on the pulse width τ are obtained in the nanosecond region by utilizing the curve fitting method.A comparison of the microwave pulse damage data and the existing dc pulse damage data for the same transistor is carried out.By means of a two-dimensional simulator,ISE-TCAD,the internal damage processes of the device caused by microwave voltage signals and dc pulse voltage signals are analyzed comparatively.The simulation results suggest that the temperature-rising positions of the device induced by the microwaves in the negative and positive half periods are different,while only one hot spot exists under the injection of dc pulses.The results demonstrate that the microwave damage power threshold and the absorbed energy must exceed the dc pulse power threshold and the absorbed energy,respectively.The dc pulse damage data may be useful as a lower bound for microwave pulse damage data.
文摘The effect of the valence band tail width on the open circuit voltage of P3HT：PCBM bulk heterojunction solar cell is investigated by using the AMPS-1D computer program. An effective medium model with exponential valence and conduction band tail states is used to simulate the photovoltaic cell. The simulation result shows that the open circuit voltage depends Iinearly on the logarithm of the generation rate and the slope depends on the width of the valence band tail. The open circuit voltage decreases with the increasing width of the band tail. The dark and light ideality factors increase with the width of the valence band tail.
基金funded by the 863 National High-Tech R&D Program of China(Grant No.2012AA101901)National Natural Science Foundation of China(Grant No.41301471)+1 种基金China Postdoctoral Special Foundation(Grant No.2013T60189)International Postdoctoral Exchange Fellowship Program(Grant No.20130043).
文摘Aerial spraying plays an important role in promoting agricultural production and protecting the biological environment due to its flexibility,high effectiveness,and large operational area per unit of time.In order to evaluate the performance parameters of the spraying systems on two fixed wing airplanes M-18B and Thrush 510G,the effective swath width and uniformity of droplet deposition under headwind flight were tested while the planes operated at the altitudes of 5 m and 4 m.The results showed that although wind velocities varied from 0.9 m/s to 4.6 m/s,and the directions of the atomizer switched upward and downward in eight flights,the effective swath widths were kept approximately at 27 m and 15 m for the M-18B and Thrush 510G,respectively,and the latter was more stable.In addition,through analyzing the coefficients of variation(CVs)of droplet distribution,it was found that the CVs of the M-18B were 39.57%,33.54%,47.95%,and 59.04% at wind velocities of 0.9,1.1,1.4 and 4.6 m/s,respectively,gradually enhancing with the increasing of wind speed;the CVs of Thrush 510G were 79.12%,46.19%,14.90%,and 48.69% at wind velocities of 1.3,2.3,3.0 and 3.4 m/s,respectively,which displayed the irregularity maybe due to change of instantaneous wind direction.Moreover,in terms of the CVs and features of droplet distribution uniformity for both airplanes in the spray swath,choosing smaller CV(20%-45%)as the standard of estimation,it was found that the Thrush 510G had a better uniform droplet distribution than the M-18B.The results provide a research foundation for promoting the development of aerial spraying in China.
基金financially supported by Ministry of Science and Technology of China(Grant No.2011CB013702)the Program for New Century Excellent Talents in University(Grant No.NCET-11-0051)
文摘Based on the elastic-plastic, large-deformation finite element method, burst capacity of steel pipeline with longitudinal corrosion defect subjected to internal pressure is studied. The appropriate stress-based criterion is used to predict the failure pressure of finite element model of corroded pipeline under internal pressure. By considering the pipe steel grades and geometries of corrosion defects, a series of finite element analyses is conducted. The effects of corrosion depth, length and width on burst capacity are also discussed. A specific failure pressure solution for the assessment of corrosion defects in moderate-to-high strength pipeline is proposed on the base of numerical results. The failure pressures predicted by the proposed method are in better agreement with the experimental results than the results by the other methods.
基金Supported by the National Natural Science Foundation of China(No.61271149)
文摘Based on the observation that both subthreshold and gate leakage depend on transistors width, this paper introduces a feasible method to fast estimate leakage current in buffers. In simulating of leakage current with swept transistor width, we found that gate leakage is not always a linear function of the device geometry. Subsequently, this paper presented the theoretical analysis and experimental evidence of this exceptional gate leakage behavior and developed a design methodology to devise a low-leakage and high-performance buffer with no penalty in area using this deviation.
基金National Natural Science Foundation of China(NSFC)(61575014)Natural Science Foundation of Beijing Municipality(4162038)
文摘A novel slotted optical microdisk resonator, which significantly enhances light–matter interaction and provides a promising approach for increasing the sensitivity of sensors, is theoretically and numerically investigated. In this slotted resonator, the mode splitting is generated due to reflection of the slot. Remarkably, effects of the slot width and angular position on the mode splitting are mainly studied. The results reveal that the mode splitting is a second function of the slot width, and the maximum mode splitting induced by the slot deformation is achieved with 2.7853 × 10~9Hz∕nm. Therefore, the slotted resonator is an excellent candidate for pressure and force sensing. Besides, the influence of the slot angular position on the mode splitting is a cosine curve with the highest sensitivity of 1.23 × 10^(11)Hz∕deg; thus, the optical characteristic demonstrates that the slotted resonator can be used for inertial measurements.
基金supported by the Fundamental Research Fund for the Central Universities(Grant No.2015JBM069)the Research Fund for Talented Scholars of Beijing Jiaotong University(Grant No.2016RC026)
文摘In steel-concrete composite twin-girder decks, wide concrete slab would undergo significant shear lag warping effect, including positive and negative. Some researchers have investigated the positive shear lag of composite decks by means of one-dimensional line model, while the studies on the negative shear lag have not yet been reported until now. In this study, a new one-dimensional analytical model of composite twin-girder decks is first proposed based on the model proposed by Dezi et al. Besides slab shear lag effect and partial connection at slab-girder interface which have been included in the model of Dezi et al., the particularity of the proposed model relies on its ability to account for variation characteristic of cross-section. Verification of the analytical model is later conducted through comparison of results from the analytical analysis and elaborate FE analysis for a simply supported composite deck with increasing depth and a two-span continuous one with decreasing depth. Finally, three kinds of structural forms of composite twin-girder decks, including cantilever, simply supported and continuous decks, are selected to carry out the analysis of positive and negative shear lag behaviors by means of the analytical model. The influences of cross-sectional variation characteristic and load type on positive and negative shear lag behaviors are mainly investigated. Additionally, a new definition on effective width for considering simultaneously positive and negative shear lag behaviors is proposed. The results from the proposed analytical model and EC4 specification are compared to provide suggestions for designers and checkers. In this study, the proposed analytical model can provide a powerful numerical tool for researchers to conduct the further investigation, and the analysis on shear lag and effective width can assist in design analysis of composite twin-girder decks.
基金supported by a grant from the Academic Research Program of Chungju National University in 2011
文摘This paper presents an experimental study investigating factors influencing the effective width of steel reinforced concrete (SRC) column-steel beam joints of building in order to calculate its resisting moment.Five 1/2 scaled interior SRC column-steel beam joint specimens were made with considering parameters such as beam flange width,beam depth and SRC column width.One directional increasing moment was applied to the joint by acting forces to each ends of beam and the structural behavior of joint was studied.And previous design method suggested by Deierlein was reviewed and a modified equation was proposed from the analysis of test result.Test result indicated that the equation to calculate the effective width in Deierlein’s design method didn’t consider effectively the influence caused by the variation of beam depth so that a modified equation was suggested and the validation of it was confirmed in this paper.
基金This research was supported by the National Key Research and Development Program of China(Grant No.2017YFD0701000)the National Natural Science Foundation of China(No.31701327)+1 种基金Jiangsu Agriculture Science and Technology Innovation Fund(CX(17)1002)Collaborative Innovation Plan of Scientific and Technological Innovation Project(Grant No.CAAS-XTCX2016006).
文摘The effective swath width(ESW)and the droplet penetration rate(DPR)directly affect the spraying quality,the spraying efficiency and the control effect of pests and diseases during the crop protection unmanned aircraft system(CPUAS)application.However,the ESW and DPR are not constant with the changes of the flight speed(FS)and the flight height(FH).In order to investigate the ESW and DPR of the CPUAS P20,four levels of FS(3 m/s,4 m/s,5 m/s and 6 m/s)and three levels of FH(1.5 m,2.0 m and 2.5 m)experiments were carried out according to the first industry standard of China for the CPUAS in the wheat field.The results demonstrated that the ESWs were negatively correlated with the FS and the FH.Most of the ESWs were over 2 m in the 12 treatments,in which the maximum one was 3.25 m(3 m/s,1.5 m).The DPRs were negatively correlated with the FH under the same FS,the average value of the DPRs was 48.37%,in which the maximum one was 78.34%(4 m/s,1.5 m)and the minimum one was 25.5%(6.0 m/s,2.5 m).The statistical analyses showed that the FS had significant impacts on the ESWs(0.01<p-value<0.05)while there were no significant differences among different FH treatments(p-value>0.05).The impacts of both FS and FH on the DPRs were extremely significant(p-value<0.01),and the interactive impacts were significant(0.01<p-value<0.05).Therefore,it is concluded that reducing the FS could increase the ESWs,and reducing the FH could increase the DRPs at the same FS.In conclusion,the maximum spraying efficiency of P20 was 4.342 hm2/h with 6 m/s FS and 1.5 m FH in case of satisfying the requirement of DPRs.This study provided scientific references for guiding the CPUAS spraying.
基金This work was partially financially supported by the National Key Research and Development Program of China(Grant No.2016YFD0200701).
文摘Unmanned agricultural aircraft system(UAAS)hasbeen widely employed as a low-cost and reliable method to apply agrochemicals to small agricultural fields in China.The performance of battery-poweredmultirotor UAAS has attracted considerable attention from manufacturers and researchers.The objective of this research was to design a UAAS equippingwith a data acquisition system,to characterize its chemical application performance based on droplet deposition data and optimize the operating parameters.Each test was repeated three times to assess the reliability of the spraying system.Various flight parameters were also evaluated.The optimal spray pressure for the XR8001 and XR8002(TeeJet,Wheaton,IL,USA)nozzles was found to be 300 kPa,and the latter nozzle had a higher droplet deposition rate and spray volume.Spray volume was not significantly affected by the flight speed or droplet density and was negatively correlated with the nozzle pressure.The results of this study provide a basis for improving the efficiency of UAAS chemicalapplication systems in terms of large-scale application.
