Abstract:It is well known that unmanned aerial vehicle (UAV) is more and more widely applied in military and civil areas. In order to play the better role of UAV, it is needed to utilize multi UAVs cooperative formation to accomplish cooperative reconnaissance, combat, defense and spraying pesticides and other tasks. The multi UAVs cooperative formation control technology mainly contains the following key techniques: data fusion technology, sensing technology, task allocation technology, path planning technology, formation control technology, communication network technology and virtual/physical verification platform technology. Firstly, summarize the research and development of key technologies worldwide. Then, the classification for multi UAVs formation control methods is mainly investigated, and the problems about formation design and adjustment, formation reconfiguration are summarized. Finally, the challenges and future development for multi UAV cooperative formation are prospected. Research shows: at present, the theory of multi UAV formation flight has acquired fruitful results, while the real cooperative formation flight test can only be implemented in the simple communication environment. The real time performance for task allocation and path planning is not high. The robustness of control methods to cope with the unexpected situation is low. The cooperative sensing ability for multi UAV with multi sensor is insufficient. The simulation of the entity is lacked. Breaking through the above key technologies, carrying out the cooperative formation flight of multi UAV in complex sensing constraints and complex communication environment, putting forward more effective control method and carrying out the UAV physical formation flying test so that the UAV can finish the task better may be the future research directions.

Abstract:For the start-up process of the LOX/CH₄ expander cycle engine, containing unobserved events and unobserved states, the existing fault diagnosis methods are still not accurate enough, so we present a diagnosis method with partially observed Petri nets. Firstly, the system observation sequences are decomposed into elementary observation sequence of length 1 and linear matrix inequalities are used to compute the firing sequences consistent with each elementary observation sequence. Then, using the forward-backward algorithm extends the diagnosis range and using the parameter K limits the length of fault diagnosis sequence. Analyzing the unobserved transitions of the fire sequences, fired or not, so as to determine whether the faults are contained among the observed sequence. Finally, the LOX/CH₄ expander cycle engine start-up process is diagnosed by the fault diagnosis system of partially observed Petri nets. The experimental results show that the proposed algorithm can reduce the computational complexity as the original h_o^-1·e^h_o-K. It avoids the state space explosion problem because of the increasing of state space complexity. Meanwhile, it can be real-time tracking and online fault diagnosis which diagnosis accuracy can be reached 99.134%.

Abstract:To overcome the higher order nonlinearity and parameters variability in the model of electric dynamic load simulator system using permanent magnet synchronous motor, a fast terminal sliding mode control approach based backstepping scheme is proposed to design a load tracking control. A whole state space model of electric dynamic load simulator system using permanent magnet synchronous motor is developed whose model uncertainties are considered as unknown external disturbances. Based on backstepping method, the model is divided into three subsystems, the fast terminal sliding-mode control law is designed to make the load tracking error converge to zero within a finite time. Through Lyapunov stability analysis, it is shown that the control strategy guarantees the asymptotic stability and a finite time convergence of the closed-loop system. Finally, Experimental results are provided to illustrate the effectiveness of the proposed control scheme. Compared with compensation control with PI and feedforward, the proposed method is more effective to eliminate the extra torque of electric dynamic load simulator. Also, the robustness and accuracy are improved obviously.

Abstract:A GPU-based spectrum reconstruction algorithm is proposed and realized aiming to meet the need for real-time spectral data processing. By analyzing the working principle and data property of snapshot Fourier transform imaging spectrometer and combining with CUDA data Parallel Processing Architecture, the article optimizes the reconstruction algorithm, including paralleling the reconstruction algorithm and optimizing the memory accessing, and implements parallel spectrum reconstruction algorithm. As a consequence, the spectrum reconstruction rate is extremely increased. The experimental results indicate that, compared with CPU serial algorithm, the GPU-based parallel spectrum reconstruction algorithm proposed in this article achieves the same reconstruction accuracy but around 25 times in computational efficiency. By taking advantage of GPU parallel computing, spectrum reconstruction efficiency is extremely improved which lays the foundation for the implementation of snapshot imaging spectrometer in real-time measurement.

Abstract:To improve conventional sensitivity factor analysis for load flow calculation that only considers three bus types: PQ, PV and Vθ, this paper proposes a sensitivity factor analysis method for bus type extended load flow calculation. By considering PQV, Qθ, QV, PQVθ extended bus types, this paper derives the sensitivity factor calculation formulas based on the correct equations of bus type extended load flow. Numerical tests given in this paper show that, when new bus types are involved in a load flow calculation, the precision of conventional sensitivity analysis method reduces obviously, whereas the proposed method can still obtain a better result. It also demonstrates the effectiveness of the derived sensitivity analysis method. By applying the proposed method, it can increase the accuracy in large-scale networks and better simulate the change of load flow.

Abstract:In order to coordinate the generator resources in longer time scales, a monthly unit commitment model of power system with integrated wind power is created. The balanced dispatch mode which can ensure medium-long electric quantity executed smoothly and the energy-saving dispatch mode which can save energy, reduce pollution has been analyzed first, then a unit commitment model coordinating electricity market and energy-saving has been build. In the model, the "pay as bell" and "benchmark price" electricity pricing mechanism has been considered. The model is based on the differential electric quantity which transfers from balanced energy, loaded generators by using the energy-saving priority list, simulated wind power scenarios considering tail-dependence and rank correlation from the previous wind power correlation analysis, and chooses the calculation resolution by thermal generator hot start & warm start characteristic. The calculated example indicates that the model can coordinate the electricity purchase cost and coal consumption under reducing the start-off times of thermal generators.

Abstract:Aiming at the time-varying fading characteristics of radio waves in coal mining face, a clustering protocol based on cross-layer is proposed. Number of active sensor nodes is recorded initially and sliding window is set up to keep optimal number of stable cluster heads in each round. The channel efficiency between nodes and base stations is calculated by probe frame, and surplus energy information is combined as a selection criterion of cluster head, to design a clustering protocol adapting to wireless signal time-varying fading. In addition, the sending power in different phases of the nodes is regulated by certain fade margin method. Simulation experiments show that compared with other three similar algorithms (LEACH, ALEACH and LEACH-SWDN), LEACH-CL protocol features stable network topology and strong adaptability under signal fading, thus effectively prolonging the network lifetime and reducing the network packet loss rate, hence it is more suitable for complex and changeable coal mining face.

Abstract:Focused on the problem that the common cyclostationary beamformer converges slowly, the robust cycliststionary beamformer based on the diagonal loading method with an adaptive shrinkage factor is proposed. The proposed method first utilizes the shrinkage factor to modify the sampling covariance matrix and naturally obtain the estimation of the covariance matrix. Then the shrinkage factor can be calculated by solving the optimal problem about the minimum mean square error between the real covariance matrix and the estimated covariance matrix. Finally using the cyclic adaptive beamforming (CAB) algorithm to achieve the weighting value of the array. Simulation results show that the proposed method converges faster compared with the traditional cyclostationary beamforming algorithm when it comes to high power of interferences or low power of interferences, and outputs higher SINR under the case of low snapshot.

Abstract:In order to improve the dynamic and robust performance of the medium frequency power supply, the robust controller is applied to the medium frequency power supply control. Based on the mathematical model of the control object, at the same time, the load and the filter inductance parameters are taken as uncertain factors, a robust controller is designed based on the μ analysis and synthesis method. Simulation and experimental results show that the dynamic response speed is improved by one times than that of the intermediate medium power supply controlled with double loop quasi PR controller, and the fluctuation of voltage in the dynamic process is reduced by nearly 40%. The medium frequency power supply controlled with robust controller not only can achieve the tracking and asymptotic stability, but also has good robust performance and strong anti-interference to the load disturbance.

Abstract:Concrete pavement is widely used due to its long service life, low maintenance requirements, low energy consumption and simple construction. However, the driving comfort of concrete pavement is normally lower than that of asphalt pavement due to the existence of cutting joints. Meanwhile, the cutting joints may reduce the durability of concrete pavement that in turn increases the maintenance cost as well. In order to solve these problems, this paper presents a novel construction technique of concrete pavement, called jointless concrete pavement. By setting low shrinkage engineered fiber reinforced cementitious composite (LSECC) strips at the place of cutting joints of conventional concrete pavement, it is possible to localize the fine cracks into the LSECC strip instead of cracking in adjacent concrete slabs. The design methods for length of the ductile strip and the parameters of anchoring bars were proposed. The concept and design method of jointless concrete pavement was successfully used in practice.

Abstract:Due to the limitations of assessment on the state of long-span bridges based on of the existing highway bridge evaluation standards, the comprehensive evaluation method of cable-stayed bridges was conducted. On the basis of the current standards for technical condition evaluation of highway bridges, a new comprehensive evaluation index system was established by introducing of some special components and long-term monitoring data. Considering the traditional weighted calculation method is easy to cover the situations of the big differences among of the indexes, a comprehensive assessment model with multi-index evidences fusion was proposed based on the credibility. In this model, a piecewise linear criterion of the evaluation index was used in underlying layer firstly. The basic confidence was determined by the membership and weight, and the fuzzy membership was calculated by the ridge type distribution function. Secondly, the confidence of the upper layer was composed by an improved Dempster combination rule. A large span cable-stayed bridge in Jiangsu Province was taken as an example, and the standard method and the improved method were analyzed based on the periodic inspection reports during 10 years. The results show that the conclusions using the advanced method agree well with the actual defects and maintenance conditions. The evaluation category is more reasonable, and the confidence set could present the state of the structure more comprehensively compared to a single value.

Abstract:To improve effects of congestion pricing, an impedance function and a traffic assignment model were introduced to explore the traffic redistribution on road network. Yingtian Street in Nanjing city was selected as the virtual charged fee example. The index differences of trip distribution, travel mode split rate, service level and travel speed pre-and-post implementing the pricing measure were used for evaluation. The results show congestion pricing could effectively lead the traffic into redistribution, and improve the traffic efficiency and service level of the network, which point out the valid effect of congestion pricing on traffic improvement. However, the results also show the improvement is not in directly proportional to the charging rate, and could get the best improvement effect when the rate is 5 yuan per time in this virtual pricing measure.

Abstract:To identify the aeroelastic effects on bridge decks during vortex-induced vibration (VIV), a new method is proposed. The procedure of instantaneous identification of the VIV system is firstly proposed. Based on this procedure, the method for extracting the aeroelastic damping and stiffness from the total damping and stiffness of the VIV system is establised. Data of wind tunnel experiments on an open-section bridge deck undergoing vortex-induced resonance is involved for validation and for studying the features of aeroelastic effects on this deck during VIV. The zero-contour of the total damping for the VIV system compares well with the experimental VIV responses, which confirms the accuracy of this method. Based on the results, aeroelastic effects at different wind velocities and amplitudes on this open-section bridge deck are studied in detail, which can offer some valuable information for the subsequent study on mathematical modeling of this phenomenon.

Abstract:In order to improve prediction accuracy of wind speed of extreme value type I distribution, the wind speed prediction model was proposed based on Jeffreys criterion and the Lindley approximation method of Bayesian theory. Monte Carl method was used to generate the pseudo wind speed samples, and the maximum likelihood parameter estimation method and Bayes statistical theory were used to estimate the wind prediction value of the extreme value type I distribution, then the prediction value was compared with the theoretical extreme value. The result indicates that the wind speed prediction model of extreme value type I distribution is more accurate than the maximum likelihood estimation. The accuracy increases with the increasing of pseudo wind speed sample numbers, but is not affected by the numbers of prior samples and prior variance for location parameter.

Abstract:To investigate the crosswind environment and flutter performances of bridge deck with different wind barriers, a single-box-girder suspension bridge with the main span of 918 m was modeled by using the CFD. The wind speed profiles and crosswind reduction factors with types of wind barriers were compared. Then, the critical flutter wind speeds and three-component force coefficients with and without the superior wind barrier (elliptic-shaped) were tested in sectional model wind tunnel tests. The diverging mechanism for two kinds of sections was studied based on 2d-3DOF method. Results show that wind barriers could effectively change crosswind environment at the range of driving height by decreasing the mean speed. The rectangular wind barrier is the best choice to reduce crosswind speed, while the elliptic wind barrier performs acceptable effects and presents a smaller drag coefficient. According to the wind tunnel test, the elliptic-shaped wind barrier could make the drag coefficient much larger than the initial section, and the critical flutter wind speed increases mildly. The analysis results by 2d-3DOF method indicate that the diverging mechanism changes quite noticeably.

Abstract:In order to investigate the load transfer mechanism of composite joint for tower of cable-stayed bridge, a segment model test with a scale of 1:3 was carried out, and the strain distribution of composite joint and the relative slippage between steel and concrete structure were obtained. A three-dimensional finite element model was established based on the test model, the structural performance of shear connectors and the effects of main parameters of composite were further investigated. The analysis results show that the stress components are at a lower level. There is a small relative slippage between steel and concrete, and both of them can bear the force collaboratively. The bearing-plate and shear connectors are main load transfer components, and could share 40% and 60% of the load respectively. Vertical shear force is at a lower level within 0.6 times length of composite joint of bearing-plate, while the vertical shear force increases gradually within 0.6-1.0 times length. The length of composite joint and the distance of shear connector have a great influence on the shear force of connector, while the diameter of the hole and the thickness of bearing-plate display a less effect.

Abstract:In order to assess the working condition of concrete box-girder bridges during operation period, an assessment method was proposed combined the structural health monitoring data and the reliability theory. The normal use limit state equation was established by considering the resistance and load effects. In this equation, the concrete tensile strength standard value was taken as the resistance while and the vehicle load response and the vertical temperature gradient load response were taken as the load effects. For comprehensive strain responses acquiring from the bridge health monitoring system, a trend term extraction method based on empirical mode decomposition was proposed. Probability density distribution fitting of the vehicle load responses and the vertical temperature gradient load responses was conducted. Then, the equivalent normalization method was used for the load effect unsatisfying the normal distribution to calculating failure probability under the most unfavorable load combinations. Results show that the monitored vehicle load responses and the vertical temperature gradient load responses are not satisfy normal distribution, and the generalized extreme value distribution could get better fitting result. Moreover, the failure probabilities of the top plate and the bottom plate of the mid-span were less than 1%, and the risk of cracking of bottom plates significantly increases under the coupling of vehicle load and vertical temperature gradient load.

Abstract:To determine permanent deformation and its accumulation characteristics of subgrade induced by long-term traffic loading in seasonally frozen regions, a calculation method is proposed based on the accumulative strain empirical of subgrade soil under cyclic loading. Then, a finite element model of base-subgrade-foundation was built, and the effects of truck type, rear-axial loading, running speed and the depth of subgrade on the stress ratio and permanent deformation in the normal and spring-thawed period are analyzed. The calculated results show that: the stress ratio decreases with the increasing of depth in the normal period, and the stress ratio in thawed soil is greater than frozen soil and normal soil. Six-axis truck could produce more permanent deformation than other four types truck. The stress ratio and permanent deformation increases with the increasing of the rear-axis loading and the thickness affected by freeze-thaw action. Stress ratio and permanent deformation decreases with the increasing of running speed. Furthermore, a prediction formulation of subgrade permanent deformation is proposed based on the above calculation results.

Abstract:To investigate the rationality of zirconium tungstate (ZT) with hydrophilia property as the filler of asphalt mixture, the surface energy parameters and work of adhesion for different fillers and binders were investigated based on the surface energy and adhesive work theory. A moisture conditioning test method applied to asphalt mastic was proposed, and then the variations of surface energy and pull-off strength of asphalt mastics were studied. Test results indicate that ZT has larger Lewis basic component and Lifshitz van der Waals component, and 70# asphalt has larger Lewis basic and acid component and Lifshitz van der Waals component when compares to SBS asphalt. ZT presents stronger adhesive bond to asphalt at dry condition than mineral filler. However, water may be easier to enter into the interface between ZT and asphalt, and replace the asphalt film on the surface of filler. Asphalt mastic made with ZT shows the worse moisture damage resistance when compares with asphalt mastic made with normal mineral filler.

Abstract:To analyze the influencing mechanism between traffic performance index (TPI) and emission factors, the speed distribution was taken as the connection variable.Firstly, a method for calculating speed distributions on different TPIs was established, and the relationship between the speed and emission factors was analyzed.Secondly, a method to calculate emission factors on road network was developed based on different TPIs, and a quantification method was analyzed to estimate the uncertainties.Thirdly, traffic emission factors on different TPIs were calculated for Beijing city.Results show that when the TPI is between 2 and 8, CO₂ emission factor increases monotonously with the increase of TPI.However, when TPI is between 0.6 and 2 or between 8 and 9.4, CO₂ emission factor increases rapidly.Finally, the average deviation rates of emission factors under different clustering results were calculated.It was concluded that by classifying the data from 4 aspects, workday, weekend, AM, and PM, the deviation rate of emission factors CO₂, CO, HC, NOx decreased from 3.48%, 6.67%, 6.08%, 6.68% to 2.65%, 5.35%, 5.20%, 5.36% respectively.

Abstract:To investigate the nondimensionalized ultimate strength and ductility behavior of stiffened steel pipe-section bridge piers subjected to a constant vertical load and cyclic lateral loads, the modified two-surface constitutive model and its finite element modeling were verified by comparing with the test results, and the effects of radius-thickness ratio, pier's slenderness ratio, stiffener's slenderness ratio and axial load ratio of the piers with eight stiffeners were investigated on the nondimensionalized ultimate strength and ductility.Some formulas based on the parametric analytical results were proposed to predict the nondimensionalized ultimate strength and ductility of piers.Numerical simulation results show that the nondimensionalized ultimate strength and ductility behaviors of the steel bridge piers could be notably improved when decreasing of radius-thickness ratio, pier's slenderness ratio, stiffener's slenderness ratio and axial load ratio.

Abstract:In order to improve the prediction accuracy of short-term traffic flow effectively, a short-term traffic flow local prediction method based on a combined kernel function relevance vector machine (CKF-RVM) model was proposed.Firstly, the C-C method was used to realize phase space reconstruction.Secondly, the number of neighboring points was determined by use of Hannan-Quinn criteria.Then, the CKF-RVM model was constructed based on particle swarm optimization algorithm.Finally, validation and comparative analysis was carried out using inductive loop data measured from the north-south viaduct in Shanghai.The experimental results demonstrate that the prediction error and the equal coefficient of the proposed method are both superior to the contrastive method.The MAPEs of the proposed method are 29.2%, 47.5% and 59.5% lower than GKF-RVM model, GKF-SVM model and weighted first-order local prediction model, which can further improve the prediction accuracy of short-term traffic flow.

Abstract:To improve the disaster prevention capacity of high speed railway, and ensure the economy and rationality of rescue sites, the constrained optimal method was used to solve the location decision-making of rescue sites on long bridges. Three constraint conditions, including the rescue sites spacing, the risk grading and the rescue time, were researched and analyzed. Least rescue time that relief vehicles reach the rescue sites from the local rescue departments was taken as optimal object, the location decision-making model of rescue sites on long bridge was established, and an example was applied to validate the model. The results show that the rescue site should set at interval of 6 km to 10 km when the bridge length is longer than 10 km. The Bayesian network theory is a feasible method to evaluate the risk grading of the alternative rescue sites, and the Dijkstra algorithm is a good way to determine the optimal path between the local rescue departments and the rescue sites. The present model is simple and reliable, and it could solve the problem of locating rescue sites on long bridges well.

Abstract:To quickly identify whether seismic high-locality landslides could threaten the line project at high-intensity mountains, potential disaster prediction of seismic high-locality landslide is proposed. According to hydrogeology condition, slope units are divided by GIS technology. Discriminant model of seismic high-locality slopes threatening line project is established. The model contains energy and path conditions. Both of two conditions are met, it can be ensured that seismic high-locality slope threatening the line project after losing stabilities. Zoning map of the seismic high-locality slopes threatening line project in study area can be obtained. Case analysis results indicate that this model approach can identify quickly which seismic high-locality landslides could threaten the line project under complex slope conditions, and provide a decision basis for location design and reconstruction of existing lines project at high-intensity mountains, and can also be used to guide designers to complete sketchy space alignment and multi-objective decision quickly in mountain.

Abstract:An analytical solution method was proposed to solve the problem of shear lag. A new shear lag warping function for the shear distribution of different cosine was constructed based on the solution of the governing equations. The trigonometric series were used to expand the shear distribution function under any given external loads, and the normal stress corresponding to each shear component was obtained separately. Finally, the superposition of normal stress was obtained and the distributions of shear lag were calculated. The energy variation method was used to derive the solution formulas based on the arbitrary warping displacement functions of shear lag effect, and a general solution procedure was developed. A rectangular simply supported box beam without cantilever plate under concentrated load and a box beam with cantilever plate under distributed load were analyzed. The calculation results show that the solution method proposed in this study could adapt well with different types of loads compared with the existing methods, and it could be effectively used for shear lag analysis of box beams subjected to arbitrary loads.

Abstract:In order to obtain reasonable aerodynamic shape of П shaped bridge decks, the buffeting performances comparison of a cable-stayed bridge was conducted based on wind tunnel tests. Firstly, three different types of П shaped bridge decks were designed based on one real cable-stayed bridge with a main span of 300 m. Secondly, force balance and vibration sectional model wind tunnel tests were carried out to obtain aerodynamic parameters under different wind attack angles. The aerodynamic parameters include three-component static wind loading coefficients, flutter derivatives, etc. Finally, three types of П shaped bridge decks' buffeting performances were compared and analyzed by considering the aeroelastic and buffeting forces. The results show that buffeting responses of the bridge with different П shaped decks are different from each other. Buffeting responses in any one freedom could be changed when changing bridge deck shape. However, the optimal influences in vertical, lateral and torsional directions could not be achieved at the same condition. Reasonable aerodynamic shape selection of П shaped bridge decks should consider the mechanical characteristics and the performances of flutter, vortex and buffeting.

Abstract:In order to obtain the relative optimal opening rate of the open-cut tunnel portal, the three-carriage high-speed train running through the hood with different opening ratios (20%-84%) at different speeds (250, 300 and 350 km/h) was modeled by using sliding mesh method, and the three-dimensional unsteady compressible Reynolds-averaged N-S equation and standard κ-ε equation turbulence formula were employed in this numerical model. Then the initial compression wave and micro pressure wave were simulated and analyzed. The results indicate that the numerical results show a well agreement with the dynamic model test, and the deviation between them is no more than 6%. The amplitude of initial compression wave increases when the hood with holes, and it increases at first stage and then decreases with the increasing of opening ratios, and reaches the maximum value when the opening ratios is 60%. The pressure gradient of initial compression wave is significantly affected by the opening rate. It decreases with increasing of the opening rate, and the amplitude shows a small change when opening rate is greater than 40%. Similarly, the effects of opening rate micro pressure wave show the same rules as the pressure gradient.

Abstract:To determine the acceleration and deceleration rate for the operating speed prediction model, the continuously driving tests of passenger car, bus, and heavy trucks were carried out on two-lane roads in a mountainous area. Longitudinal acceleration of vehicles was collected, and the cumulative frequency curves of peak acceleration and deceleration rate were analyzed. The statistical distribution and the eigenvalues of acceleration (a_x) and deceleration (a_b) were obtained, and the models of a_x and a_b with road geometry parameters as independent variables were established. The results show that: due to that the magnitude of a_b of passenger cars is about twice higher than a_x, the a_x and a_b could not be simplified to a same fixed value. Slope breakpoint of cumulative frequency curve of a_x and a_b does not appears on the 85^th percentile but near the 95^th percentile. The a_x and a_b of large buses display very close amplitude, and a_b of heavy-duty trucks is significantly greater than a_x. a_x and a_b of heavy-duty trucks are lower than large buses'. There is a negative correlation between longitudinal acceleration of passenger car and curve radius, and a positive correlation with curve deflection angle.