In the 1990s, several major earthquakes occurred throughout the world, with a common observation that near fault ground motion （NFGM） characteristics had a distinct impact on causing damage to civil engineering stru...In the 1990s, several major earthquakes occurred throughout the world, with a common observation that near fault ground motion （NFGM） characteristics had a distinct impact on causing damage to civil engineering structures that could not be predicted by using far field ground motions. Since then, seismic responses of structures under NFGMs have been extensively examined, with most of the studies focusing on structures with relatively short fundamental periods, where the traveling wave effect does not need to be considered. However, for long span bridges, especially arch bridges, the traveling wave （only time delay considered） effect may be very distinct and is therefore important. In this paper, the results from a case study on the seismic response of a steel arch bridge under selected NFGMs is presented by considering the traveling wave effect with variable apparent velocities. The effects of fling step and long period pulses of NFGMs on the seismic responses of the arch bridge are also discussed.展开更多
Wing-Wing Interaction （WWI）, such as the Clap and Fling Motion （CFM）, occurs when two wings are flapping close together, improving performance. We intend to design a hovering Flapping Micro Aerial Vehicle （FMAV）...Wing-Wing Interaction （WWI）, such as the Clap and Fling Motion （CFM）, occurs when two wings are flapping close together, improving performance. We intend to design a hovering Flapping Micro Aerial Vehicle （FMAV） which makes use of WWI. We investigate the effects of flexibility, kinematic motions, and two- to six-wing flapping configurations on the FMAV through numerical simulations. Results show that a rigid spanwise and flexible chordwise wing produces the highest lift with minimum power. The smoothly varying sinusoidal motion, which is visually similar to the CFM, produces similar lift in comparison to the CFM, while having lower peak power requirement. Lastly, lift produced by each wing of the two-, four-, six-wing configurations is approximately equal. Hence more wings generate higher total lift force, but at the expense of higher drag and power requirement. These results will be beneficial in the understanding of the underlying aerodynamics of WWI, and in improving the performance of our FMAV.展开更多
This paper presents a technique to reproduce compatible seismogran3s involving permanent displacen3ent effects at sites close to the fault source. A multi-objective evolutionary algorithm is used to minimize the diffe...This paper presents a technique to reproduce compatible seismogran3s involving permanent displacen3ent effects at sites close to the fault source. A multi-objective evolutionary algorithm is used to minimize the differences between the response spectra and multi-tapered power spectral delsilies corresponding to the recorded and simulated wavelbrms. The multi-taper method is used to reduce the spectral leakage that is inherent in the Fourier rams formed form ofwavelbrms, ieading to a reduction of variance in power spectral amplitudes, thus permitting the calibration of the two sets of data. The technique is implemented using the 1998-Fandoqa （lran） earthquake data and the results are compared with the actual observed data. Additionally, a comparison is made with a SAR interfcrometry study leading to fair agreement with the reported dislocation along the main fault. The simulation procedure and results are discussed and assessed concluding that, although the technique may be associated with uncertainties, it can still be used to reproduce wavelbnns at near source sites that include permanent dislocation, and can be used for seismic pertbrmance evaluation of structures in the region under study.展开更多
Several filter techniques were available for the GPS position estimation problem of maneuvering vehicle ranging from using different process noises to Interactive Multiple Model (IMM). The limitation of using standard...Several filter techniques were available for the GPS position estimation problem of maneuvering vehicle ranging from using different process noises to Interactive Multiple Model (IMM). The limitation of using standard Kalman filters is listed.The performance of proposed adaptive filter is compared with that of the standard ones,two types of dynamic modeling of the maneuvering vehicle are used.The simulation is based on the almanac data of the GPS satellites to compute its feasibility during the simulation time and position on shape 8 track with continuous vehicle maneuvering. The goal is to obtain computationally efficient filter with reasonable accuracy for vehicle in maneuvering situation. The filter proposed is an alternative to the filter proposed in Ref. [1] with low computational burden.展开更多
Compared with single agronomic practices management during grain formation, knowledge about integrated agronomic practices management on grain-filling characteristics and physiological function of endogenous hormones ...Compared with single agronomic practices management during grain formation, knowledge about integrated agronomic practices management on grain-filling characteristics and physiological function of endogenous hormones was limited. In order to clarify this issue, two field experiments, integrated agronomic practices management(IAPM), T1(local conventional cultivation practices), T2(an optimized combination of cropping systems and fertilizer treatment), T3(treatment based on high-yield studies), and T4(further optimized combination of cropping systems and fertilizer treatment), and nitrogen rate testing(NAT)(four nitrogen rates, 0, 129.0, 184.5, and 300.0 kg N ha–1) were performed with summer maize hybrid Zhengdan 958(ZD958). Results showed that with increased nitrogen rate, the endogenous hormone balance was promoted and the grain-filling characteristics were improved sufficiently to resulting in a significant increase in grain yield. However, the grain-filling characteristics deteriorated and yield was reduced with excessive nitrogen fertilization. However, IAPM could promote hormone balance and improve grain filling characteristic. The indole-3-acetic acid(IAA), zeatin riboside(ZR), and gibberellin(GA3) contents under T2 and T4 treatments were higher and the abscisic acid(ABA) content was lower, and the ZR and GA3 contents under T3 were higher than those under T1. Those resulted in the maximum grain-filling rate(Wmax) and the active grain-filling period(P) under T2, T3 and T4 were significantly increased than those under T1, and hence promoted kernel weight and grain yield. So IAPM promoted hormone balance by improving tillage model, optimizing fertilizer rate and fertilization period, appropriately increasing planting density and delaying harvest, which promoted grain filling rate and lengthened active grain-filling period, finally increased grain yield.展开更多
Hovering ability is one of the most desired features in Flapping-Wing Micro Air Vehicles （FW-MAVs）. This paper presents a hybrid design of flapping wing and fixed wing, which combines two flapping wings and two fixe...Hovering ability is one of the most desired features in Flapping-Wing Micro Air Vehicles （FW-MAVs）. This paper presents a hybrid design of flapping wing and fixed wing, which combines two flapping wings and two fixed wings to take advantage of the double wing clap-and-fling effect for high thrust production, and utilizes the fixed wings as the stabilizing surfaces for inherently stable hovering flight. Force measurement shows that the effect of wing clap-and-fling significantly enhances the cycle-averaged vertical thrust up to 44.82% at 12.4 Hz. The effect of ventral wing clap-and-fling due to presence of fixed wings produces about 11% increase of thrust-to-power ratio, and the insect-inspired FW-MAV can produce enough cycle-averaged vertical thrust of 14.76 g for lift-offat 10 Hz, and 24 g at maximum frequency of 12.4 Hz. Power measurement indicates that the power consumed for aerodynamic forces and wing inertia, and power loss due to gearbox friction and mechanism inertia was about 80% and 20% of the total input power, respectively. The proposed insect-inspired FW-MAV could endure three-minute flight, and demonstrate a good flight performance in terms of vertical take-off, hovering, and control with an onboard 3.7 V-70 mAh LiPo battery and control system.展开更多
基金Federal Highway Administration(FHWA) Under Grant No.DTFH41-98900094
文摘In the 1990s, several major earthquakes occurred throughout the world, with a common observation that near fault ground motion （NFGM） characteristics had a distinct impact on causing damage to civil engineering structures that could not be predicted by using far field ground motions. Since then, seismic responses of structures under NFGMs have been extensively examined, with most of the studies focusing on structures with relatively short fundamental periods, where the traveling wave effect does not need to be considered. However, for long span bridges, especially arch bridges, the traveling wave （only time delay considered） effect may be very distinct and is therefore important. In this paper, the results from a case study on the seismic response of a steel arch bridge under selected NFGMs is presented by considering the traveling wave effect with variable apparent velocities. The effects of fling step and long period pulses of NFGMs on the seismic responses of the arch bridge are also discussed.
文摘Wing-Wing Interaction （WWI）, such as the Clap and Fling Motion （CFM）, occurs when two wings are flapping close together, improving performance. We intend to design a hovering Flapping Micro Aerial Vehicle （FMAV） which makes use of WWI. We investigate the effects of flexibility, kinematic motions, and two- to six-wing flapping configurations on the FMAV through numerical simulations. Results show that a rigid spanwise and flexible chordwise wing produces the highest lift with minimum power. The smoothly varying sinusoidal motion, which is visually similar to the CFM, produces similar lift in comparison to the CFM, while having lower peak power requirement. Lastly, lift produced by each wing of the two-, four-, six-wing configurations is approximately equal. Hence more wings generate higher total lift force, but at the expense of higher drag and power requirement. These results will be beneficial in the understanding of the underlying aerodynamics of WWI, and in improving the performance of our FMAV.
文摘This paper presents a technique to reproduce compatible seismogran3s involving permanent displacen3ent effects at sites close to the fault source. A multi-objective evolutionary algorithm is used to minimize the differences between the response spectra and multi-tapered power spectral delsilies corresponding to the recorded and simulated wavelbrms. The multi-taper method is used to reduce the spectral leakage that is inherent in the Fourier rams formed form ofwavelbrms, ieading to a reduction of variance in power spectral amplitudes, thus permitting the calibration of the two sets of data. The technique is implemented using the 1998-Fandoqa （lran） earthquake data and the results are compared with the actual observed data. Additionally, a comparison is made with a SAR interfcrometry study leading to fair agreement with the reported dislocation along the main fault. The simulation procedure and results are discussed and assessed concluding that, although the technique may be associated with uncertainties, it can still be used to reproduce wavelbnns at near source sites that include permanent dislocation, and can be used for seismic pertbrmance evaluation of structures in the region under study.
文摘Several filter techniques were available for the GPS position estimation problem of maneuvering vehicle ranging from using different process noises to Interactive Multiple Model (IMM). The limitation of using standard Kalman filters is listed.The performance of proposed adaptive filter is compared with that of the standard ones,two types of dynamic modeling of the maneuvering vehicle are used.The simulation is based on the almanac data of the GPS satellites to compute its feasibility during the simulation time and position on shape 8 track with continuous vehicle maneuvering. The goal is to obtain computationally efficient filter with reasonable accuracy for vehicle in maneuvering situation. The filter proposed is an alternative to the filter proposed in Ref. [1] with low computational burden.
基金We are grateful for grants from the National Basic Research Program of China(2015 CB 150404)the earmarked fund for China Agriculture Research System(CARS-02-18)the Funds of Shandong“Double Tops”Program,China(SYL2017YSTD02).
文摘Compared with single agronomic practices management during grain formation, knowledge about integrated agronomic practices management on grain-filling characteristics and physiological function of endogenous hormones was limited. In order to clarify this issue, two field experiments, integrated agronomic practices management(IAPM), T1(local conventional cultivation practices), T2(an optimized combination of cropping systems and fertilizer treatment), T3(treatment based on high-yield studies), and T4(further optimized combination of cropping systems and fertilizer treatment), and nitrogen rate testing(NAT)(four nitrogen rates, 0, 129.0, 184.5, and 300.0 kg N ha–1) were performed with summer maize hybrid Zhengdan 958(ZD958). Results showed that with increased nitrogen rate, the endogenous hormone balance was promoted and the grain-filling characteristics were improved sufficiently to resulting in a significant increase in grain yield. However, the grain-filling characteristics deteriorated and yield was reduced with excessive nitrogen fertilization. However, IAPM could promote hormone balance and improve grain filling characteristic. The indole-3-acetic acid(IAA), zeatin riboside(ZR), and gibberellin(GA3) contents under T2 and T4 treatments were higher and the abscisic acid(ABA) content was lower, and the ZR and GA3 contents under T3 were higher than those under T1. Those resulted in the maximum grain-filling rate(Wmax) and the active grain-filling period(P) under T2, T3 and T4 were significantly increased than those under T1, and hence promoted kernel weight and grain yield. So IAPM promoted hormone balance by improving tillage model, optimizing fertilizer rate and fertilization period, appropriately increasing planting density and delaying harvest, which promoted grain filling rate and lengthened active grain-filling period, finally increased grain yield.
文摘Hovering ability is one of the most desired features in Flapping-Wing Micro Air Vehicles （FW-MAVs）. This paper presents a hybrid design of flapping wing and fixed wing, which combines two flapping wings and two fixed wings to take advantage of the double wing clap-and-fling effect for high thrust production, and utilizes the fixed wings as the stabilizing surfaces for inherently stable hovering flight. Force measurement shows that the effect of wing clap-and-fling significantly enhances the cycle-averaged vertical thrust up to 44.82% at 12.4 Hz. The effect of ventral wing clap-and-fling due to presence of fixed wings produces about 11% increase of thrust-to-power ratio, and the insect-inspired FW-MAV can produce enough cycle-averaged vertical thrust of 14.76 g for lift-offat 10 Hz, and 24 g at maximum frequency of 12.4 Hz. Power measurement indicates that the power consumed for aerodynamic forces and wing inertia, and power loss due to gearbox friction and mechanism inertia was about 80% and 20% of the total input power, respectively. The proposed insect-inspired FW-MAV could endure three-minute flight, and demonstrate a good flight performance in terms of vertical take-off, hovering, and control with an onboard 3.7 V-70 mAh LiPo battery and control system.
