Abstract:To understand the disaster-causing mechanism of fault slip rockburst and reduce incidence of rockburst during mining process, the research progress and achievements of the rockburst are summarized and analyzed by combing literatures at home and abroad. Firstly, severe situations and some cases of the rockburst are presented and analyzed. Secondly, the disaster-causing mechanism of the rockburst is analyzed from the mechanism and criteria of fault reactivation, fault slip rockburst theories, produced conditions and generation process of the rockburst. Thirdly, the monitoring and early warning methods of the rockburst are summarized, and the monitoring and controlling technology system of the rockburst, BMS-Ⅱ type microseismic monitoring system, multi-parameter monitoring and early warning system, and deep borehole strain observation technology are presented. Fourthly, the preventing and controlling technologies for the rockburst are summarized, including regional defense measures and local relief measures. Finally, some shortcomings of the current research on the rockburst are pointed out, and the development tendencies of future research on the rockburst are prospected in many aspects.

Abstract:To investigate the dynamic behavior of lightweight aggregate concrete under uniaxial compression, the displacement controlled uniaxial compression experiments were carried out together by considering five loading rates and four loading areas, and the stress-strain curves of lightweight aggregate concrete were obtained. The effects of loading rates and loading areas on the peak stress, peak strain and elastic modulus were analyzed and discussed. The constitutive model of viscoelastic and plastic damage of concrete was developed by correcting the model parameters, and the rationality of proposed model was verified through experimental data. Results show that loading rates and loading areas have a significant effect on stress-strain curves of the concrete. Loading areas exhibit greater effects on elastic modulus, peak stress and peak strain of the lightweight aggregate concrete. The proposed model can accurately describe the strain rate effect and nonlinear behavior of the lightweight aggregate concrete under dynamic loading.

Abstract:To obtain the transfer information of passengers' public transit behavior, a public transit transfer recognition method is designed based on multi-class support vector machine (multi-class SVM). GPS data and intelligent card data are fused to get sufficient samples, then the Multi-class support vector machine model is used to train the samples. The best sample size could be acquired by accuracy control, and the Grid-Search method combined with Particle Swarm Optimization method is employed to determine the parameter for gaining the optimal SVM model. Finally, a case study with GPS data and intelligent card data in Foshan city is conducted to verify the algorithm, this method can acquire transfer characteristics including transfer flow and transfer proportion etc. Results show that the proposed method could complete public transit transfer recognition with high classification accuracy even if the size of training sample is rather small. Especially, it is useful for transfer recognition in large cities with complex public transit networks, which provides a basis for public transit lines planning and pub selection.

Abstract:To research the adhesive properties of polyurethane sealant under shear fatigue loading, a test method for evaluating the adhesive properties of sealants was developed based on the in-situ working condition. Direct tension tests at low temperature were conducted on the samples subjected to various shear fatigue cycles, the effects of various sealants on the maximum tensile force, failure displacement and force-displacement curves were analyzed and compared between experienced and un-experienced shear fatigue loading. The results show that the isocyanate index R of the samples un-experienced shear fatigue loading presents the positive correlation with bonding strength, and negative correlation with deformation resistivity. However, the R value presents a negative correlation with fatigue resistivity of sealants for the samples experienced shear fatigue loading. The adhesive properties and discreteness of sealants were improved due to chain orientation within sealants at the initial period of fatigue cycles. During the fatigue cycles, the stability of maximum force index is superior to the failure displacement due to the discontinuous medium of sealant body. As the increase of fatigue cycles, the accumulation of damage breaks the integrality of the bonding interface, which leads to the change of failure mode from brittle failure to ductile failure. Based on the test results, the sealants with R values between 1.7~2.5 could present better shear fatigue resistance performances.

Abstract:To reduce the workload of air traffic operators in airport surface operation, curtail the cost of taxi-out and the pollutant emission, a new gate-hold penalty-based departure pushback control strategy was proposed based on the traditional N-control strategy. The algorithm could search the optimal threshold for taxiway queuing system, and require the pushback rate changes with the real-time taxiway queue length. Taken the pushback operational cost as objective function, the control strategy model and its two various forms were carried out, and an iterative Markov chain-based optimization algorithm was developed to solve the model. Simulation results with PEK airport data indicate that the proposed pushback strategy could transfer taxiway waiting time into gate-hold time to minimize the total operational cost. The strategy could save 2 995 minutes per day on total taxi-out time and 44.04% fuel burn cost than situation of without pushback strategies, also reduce departure operational cost effectively.

Abstract:To improve calculation efficiency of the coupled vibration between random traffic flow and bridge, an innovative time domain analysis method is proposed. The traffic-bridge coupled vibration equation is established by combing the modal synthesis technology and global analysis method. The dimension of motion equation for random vehicles and bridge system is updated constantly based on the progress evaluation for the running vehicles on the bridge, and the algorithm of dynamic storage and extraction for procedural computing data is proposed. The whole framework and detailed implementation steps also are introduced for the proposed traffic-bridge coupled vibration analysis method. Numerical results indicate that the computing cost of the proposed method is 14.5% of the traditional integral method, and it is similar with the separated iterative method when relative errors are less than 3.5%. The proposed method has a good computing efficiency and accuracy, and can be used to the random traffic load and bridge coupled vibration analysis.

Abstract:To investigate the performances of reinforced concrete columns under rockfall impact, a damage state analysis method for RC columns is proposed by considering the strain rate effect of dynamic shear capacity. Firstly, the accuracy and predicting capacity of proposed FE model are validated with a drop weight test, and then a FE model of the substructure of Chediguan Bridge is established regarding the interaction between piles and soil layers. Secondly, the static shear capacity of RC columns is considered by the equations presented by Priestley, and the strain rate effect of the concrete is described by K&C model. Then, a series of cases are conducted to obtain the damage degree of RC columns subjected to varying impact conditions. Finally, the effect of sectional area of columns, transverse reinforcement ratio, concrete strength and the slenderness ratio on the shear damage degree of the columns are examined through a parametric analysis. Results show that the global average method exhibits a disadvantage since the descent stage of rockfall impact force-time history has a longer duration, it would lead to a low equivalent static load under high impact strength. The proposed analysis approach can more accurately evaluate the damage state of RC columns subject to rockfall impact by considering dynamic shear capacity. The parametric analysis results show that the increasing of the sectional area and transverse reinforcement ratio inordinately reduce the damage level of RC columns.

Abstract:To investigate the seismic behaviors of partially encased composite girder with corrugated steel web and composite girder with stiffened corrugated steel web, the pseudo static models tests with shear span ratio of 1.67 were conducted. The basic seismic performances including failure features, hysteretic curves, load-carrying capacity, ductility, strength and stiffness degradation, energy dissipation and deformation recovery ability were analyzed. The results indicate that the partially encased specimen presented bending-shear failure with local buckling of the corrugated steel web, while the stiffened one was failed by shearing and overall buckling of the web. In addition, the inclined cracks appeared at the end of fixed part for all tested bodies. Compared with the stiffened girder, the partially encased one exhibited a higher load-carrying capacity, ductility and energy dissipation ability. These two kinds of webs can improve the stability of the corrugated steel web, the hysteretic curves are relatively plump and the strength degradation coefficients are greater than 0.9, the viscous damping coefficients are more than 0.2, and the residual deformation ratios are less than 0.61. All of these data indicate that the proposed webs have the smaller strength degradation, and greater energy dissipation and deformation recovery ability.

Abstract:To investigate the relationship of strain between the high strain-hardening UHPC and the reinforcement when the flexural failure of beams occurred, one-third loading experiments were carried out on five girder specimens. During the tests, the change parameters of the specimens are the reinforcement percentage and the type of reinforcement. Firstly, the load-deflection curves of reinforcement and high strain strengthening UHPC indicate that T-beam failure process could be divided into three stages: the elastic stage, the fracture development stage and the load-to-failure stage. Secondly, the cooperation between reinforcement and UHPC was discussed based on the load-strain curves of reinforcement and high strain-strengthening UHPC. Finally, the loading process was divided into four stages according to the stress-strain curves of reinforcement and high strain-strengthening UHPC. The results show that the reinforcement rebar and the UHPC present reliable cohesiveness and could keep the strain consistent before the reinforcement reaches the yield strain. The resistance of high strain-hardening UHPC tensile strength plays more important proportion than reinforcement rebar during the flexural process, and it could be bigger at a low percentage of reinforcement. It is suggested that the tensile strength of UHPC should be taken into account when calculating the bearing capacity of high strain-hardening UHPC, and ensure the accuracy of the calculation method of bearing capacity.

Abstract:To improve signal timing and traffic flow operation at the intersection with contraflow left-turn lane, the application condition for the contraflow left-turn lane was developed. The arrival and discharge pattern of left-turn vehicles were divided into 8 groups and the calculation method for left-turn vehicle delay under each group was carried out. The average intersection vehicle delay minimum was taken as the objective, cycle length, green times of main and pre-signal phases, and the lengths of contraflow left-turn lanes were taken as optimization variables, and then the signal control plan optimization model was developed. The genetic algorithm was used to solve this model. A case study was conducted to validate the optimization method, which was also compared with the traditional control method. Results show that the optimization method can increase the capacity of left-turn vehicles, decrease the required green time and then reduce the intersection cycle length. The decrease in the green time of left-turn phases would result in the decrease in the red time of through phases and then the decrease in intersection average delay. In peak hour, average vehicle delay can be decreased by 23.8%.

Abstract:To improve the prediction accuracy of intersection short-term traffic flow, a new CEEMDAN-PE-OSELM model is developed based on the complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN), permutation entropy(PE) and online sequential extreme learning machine(OSELM). Firstly, traffic flow historical time series are decomposed by CEEMDAN algorithm. Secondly, PE algorithm is used to recombine the IMF components obtained by CEEMDAN, and a series of restructured subsequences can be obtained, which have a significant difference in terms of complexity. Then, the OSELM prediction models are proposed for each restructured subsequence respectively, and the final results are got by adding the prediction results. Finally, a typical intersection is verified the effect and performance of the hybrid prediction model. Results show that the values of MAE, MAPE and MSE of CEEMDAN-PE-OSELM prediction model are lower than other models, and get a minimal error. The EC value of the improved model is 0.963, which is higher than that of ARIMA model (0.898) and the most close to 1. The CEEMDAN-PE-OSELM prediction model has the highest precision and best stability, and the errors decrease obviously.

Abstract:Due to the aerial camera CCD (charge coupled device) existing limited dynamic range, it cannot reveal all the details in a high-dynamic range scene. To solve this problem, this paper presents a multi-exposure fusion method based on illumination estimation in complex wavelet domain. First, a set of multi-exposure images are obtained by multiple expose in the same scene, and register these images using the fast small-area registration strategy based on SURF (speeded up robust feature). Then the illumination of these images is estimated. In complex wavelet domain, weights according to the illumination are assigned to the low component for fusion; and weighted regional energy based fusion rule is adopted for high component fusing. Finally, fused image is acquired by subjecting the low and high component to inverse DT-CWT. The results obtained by this method are performing well in spatial frequency, figure definition, average gradient and edge preservation information. Experiments demonstrate that images obtained by this paper have appropriate brightness and preserve the details and edges effectively. It is suitable for varied high dynamic range scenes and conforms to the requirements of aviation investigation.

Abstract:To detect the depth, area and volume of potholes automatically, three test bodies with different sizes were scanned by 3D line laser technology. TIN plane interpolation method was employed to reconstruct the 3D laser-point cloud data model, and a combination of contour line pick-up algorithm was used to calculate multi-dimension indexes of potholes. The ASTM experimental criteria was adopted to verify the validity of index calculating method, and the error rules of depth, area and volume indexes of potholes in different sizes were analyzed. Results show that the maximum relative errors of depth, area and volume of potholes were 4.60%, 3.87% and 10.82%, respectively, and the relative errors of depth and area decrease with increasing of potholes sizes. Accurate detection of multi-dimension index of potholes could be achieved with utilization of line laser technology, and this proposed method could provide the basis for fast and accurate judgement of severity of potholes, determination of damage level and estimation of repair materials.

Abstract:To obtain the best classification results of logistics park, the qualitative division of logistics park traffic zones is carried out, then the weighted fuzzy similar matrix is constructed, and the adjacency matrix is used to amend the weighted fuzzy similar matrix. The improved fuzzy clustering method is employed to the clustering of merger of logistics park traffic zones. In addition, the F index is constructed to determine the optimal number of class based on the distance in the class and the distance between the class. The results show that the improved fuzzy clustering method could greatly reduce the amount of logistics park traffic zones, and it can quickly get the better logistics park traffic zones classification and avoid dividing logistics park traffic zones which are in the non-adjacent geographical position into the same class.

Abstract:To overcome shortcomings and improve calculation accuracy of the common seismic fragility analysis method, the kernel density estimation method (KDE) is introduced and used to analysis the seismic fragility of bridge structures. A typical four span railway rigid frame-continuous beam bridge with high pier was taken as engineering case, and the fragility analysis of this bridge was carried out. The calculation result by using of KDE method was validated by using of Monte Carlo method, and then was compared with traditional methods (cloud method, maximum likelihood estimation method). Result shows that the KDE method could overcome the shortcomings of common fragility analysis methods of bridge and presents a good stability, and also improves the computational efficiency of seismic fragility analysis method on the premise of ensuring the accuracy. The calculation accuracy of cloud method is the lowest among of the using methods, and the KDE method was suggested to use for seismic vulnerability analysis of bridge. The seismic fragility curves could be applied to evaluate the performances of bridge seismic.

Abstract:To explore the potential evaluating methods of regional sponge city under the context of urban flood, this paper establishes the potential indicator system of sponge city from the perspectives of rainfall, water pollution, flood disaster and ecological green land. Because these four elements are closely related with sponge city. Taking the national-level Tianfu District as an example, the regional index system is studied comprehensively by using the methods of mathematical statistics, fuzzy neural network, fuzzy synthetic evaluation and satellite image recognition; besides, the construction potential of Tianfu District sponge city is evaluated with the methods of gray correlation analysis quantitatively; moreover, the potential index ranking of every sponge city in every district and county is given. Finally, a new drainage system is developed according to flood disaster. The results show that it is relatively objective to evaluate the sponge city potential from the above four aspects, namely, rainfall, water pollution, flood disaster and ecological green land; also, the indicator vector of Shuangliu Area has the minimum correlation with the ideal indicator vector, which means this area is the most proper and potential place to carry out the sponge city construction in Tianfu District; furthermore, the developed underground drainage system can alleviate problems of city waterlogging, water quality and pipe network pressure and so on. The mentioned evaluating methods of the potential of sponge city and the developed underground drainage system can provide references for promoting the construction of sponge city.

Abstract:To investigate the effects of sustained load on bonding properties of CFRP (Carbon Fiber Reinforced Polymer)-concrete interface, the ultimate debonding load of interface P_u was determined by three double shear specimens, and twenty-four double shear tests were performed under four load levels and four duration days of 5, 10, 15, 30, 60 and 90 for each load level. Results indicated that the interfacial slip s₀ corresponding to the peak interfacial shear stress τ_max was reduced under sustained load, but reduction magnitude shows an un-notable correlation with the duration and amplitude of load. The slip s₀ reduces by about 50% after the load duration for ninety days. When the load is greater than 0.5P_u, the peak shear stress τ_max closed to loading position ranging of 15 mm decrease with the increase of load level and duration, but exhibit un-notable changes in other position. Finally, the bond slip constitutive model of CFRP-concrete interface under sustained load was proposed based on these test data. The failure test showed that there was no significant effect of sustained load on the ultimate debonding load when the bonding length is greater than the effective bonding length, but the peeling load P_db of interface during the first stripping in the debonding process was reduced due to the sustained load. When the loads of 0.5 P_u, 0.7 P_u, 0.9 P_u last for 90 days, the peeling loads P_db reduce by 42%, 54%, 66% respectively.

Abstract:To investigate mechanical properties of active layer in permafrost due to the freeze-thaw cycles, a series of the unconsolidated and undrained triaxial shear tests were conducted by considering the factors of different freezing temperatures, degree of compaction, numbers of freeze-thaw cycles, moisture content and confining pressures. The stress-strain curve, failure strength, elastic modulus and shear strength parameters of sandy silt were determined and analyzed, and significance analysis of the five factors and interactions among of them were carried out. Results show that with the increase of freeze-thaw cycles, the failure strength and elastic modulus, measured at the confining pressures of 300 kPa and at the freezing temperatures of -5 ℃, increase at the first three freeze-thaw cycles and then attain a stable status. Cohesion force decreases gradually and tends to be stable at the freezing temperatures of -5 ℃, and increase firstly and then drop, finally attain a stable status at the freezing temperatures of -10 ℃ and -15 ℃. All factors have a significant influence on the mechanical properties except freezing temperature. Interactions between degree of compaction and moisture content, confining pressure and number of freeze-thaw cycles exhibit a significant effect on failure strength. Significant analysis indicates that interactions of factors should be considered in the test design.

Abstract:To detect the fault of the main transformer windings for AC locomotive without changing the original structure of the locomotive system, a non-invasive on-line winding fault diagnosis method for the main transformer is proposed. Proved by the mathematical theory, the relationship between ΔV-i₁ is a diagonal ellipse whose center is located at the origin of rectangular coordinate system. The related parameters of the ellipse vary with the change of the winding faults. Then, the feasibility and effectiveness of the proposed method are verified by experiment through dSPACE simulations. The results show that with the increase of short circuit percentage, the area of ellipse increases and the centrifugal rate decreases. When the axial displacement is increased, the centrifugal rate increases, while the elliptical length, short axis and its area decrease. When short-disk occurs, the elliptical short axis decreases and the inclination angle changes obviously. By comparing the ΔV-i₁ trajectory under normal and fault condition, the fault type and fault level can be determined.

Abstract:To satisfy the comfortable demand for passengers during peak period in a low service level, the on-bus service level is divided into four grades with a standard of standing-passenger density based on the theory of computer visual simulation. An improved on-bus perceived value model of different service is proposed with the introduction of passengers' income, and the average of perceived value for different service level under different income of passengers is obtained. Furthermore, the model of departure interval considering passengers' perceived cost is formulated. The model was applied to the 649 bus route in Tianjin City, and the optimal departure time in peak period is derived based on MATLAB. Results show that it is necessary to consider passenger's perceived cost when the on-bus perceived value is 38%-69% in total during peak period. Passenger's perceived cost is cut down sharply while bus company basic interests be guaranteed. It reflects people-based service concept and may provide important scientific support with promoting the attraction of bus systems.

Abstract:To optimize the hazardous materials (hazmat) transportation paths in dynamic road networks and make a decision on path selection for carriers, the stochastic time dependent (STD) characteristics of transport networks were analyzed, the travel time and the number of people affected around each link were fitted in piece-wise continuous time interval. The 0-1 integer programming model was formulated by taking the arrival time window as a constraint, and taking the stochastic attribute values of travel time and transport risk as optimization criteria. A two-stage multi-dimensional label correcting algorithm was designed with First-In-First-Out property of the STD road networks, and the non-dominated paths were generated at different departure time to meet the time window constraint with predetermined confidence level. The criterion-weight and threshold-dominate methods were proposed to balance computational efficiency and accuracy. Research results indicate that the travel time and transport risk of hazmat in STD road networks are related to the setting of arrival time window and the selection of departure time. The non-dominated path depends on the departure time and the choice of carrier's preference, and the amount of non-dominated paths depends on the dominated threshold value. Different types of carriers can choose the optimal combination of departure time and transportation path according to the confidence level of arriving on time.

Abstract:The variation of synchronous grouting pressure has a significant effect on the internal force distribution of adjacent segments. To control grouting pressure accurately and keep safety during shield driving, the grout pressure distributions in space-time domain were investigated. By considering of time-variation behavior of grout viscosity and permeability, the process of grout filling, diffusion and dissipation during shield backfilled grouting were united. Then, the theoretical formulas of grouting pressure distribution along the circular and longitudinal direction of segments were built. Finally, a grout rheological test and numerical models were conducted based on the engineering case, and the time-space distribution law of grout pressure acting on tunnel segments were obtained and analyzed. The results show that the grout consolidation and pressure dissipation during synchronous grouting have notable influence on distribution of grouting pressure along segments. The increase of grout viscosity and decrease of grout liquidity and permeability of soil layers affect the extent of grouting pressure dissipation, and then affect the distribution of internal force of tunnel segments. The mechanical features of segments calculated from numerical models are closer to field measured data when considering the time-varying effect of grout viscosity. The research results provide a guideline for fine analysis of segment mechanics during construction.

Abstract:To avoid the ship collision automatically, the domain concept of navigation obstruction and the theory of dynamic boundary are employed to establish the ship domain model and dynamic static obstacles model. Then, the ship collision risk quantification model is deduced by considering the factors of shallow bottom, quay, wind and current. Observing from the ship, the ship automatic collision avoidance in restricted waters is modeled based on the operating performance of the ship and the collision risk of the static obstacles and dynamic target, and the current environmental factors, and combining the potential field theory and the theory of ship collision avoidance, ship domain bound theory. Numerical simulation results show that the ship controlled by the automatic collision avoidance model could sail safely in restricted waters regions, and the limitations of traditional potential field model were solved.

Abstract:Aiming at the problem that the navigation accuracy of strapdown inertial navigation system (SINS) is severely affected by oscillation errors, an external damping strapdown inertial navigation algorithm based on double filters is presented. Two serial filters are designed for the algorithm. First filter uses the external velocity as the reference input to estimate errors of strapdown inertial navigation system and the external velocity is smoothed at the same time. Employing the high-precision external velocity smoothed by first filter as the input, second filter conducts error state estimation process and eliminates the influence of velocity constant error on the system. At last, information fusion algorithm is designed to give consideration to advantages of both filters. Simulation results show that, in the presence of external velocity constant error, this algorithm has higher steady-state precision and reduces the convergence time of system errors, which effectively improves the navigation accuracy of strapdown inertial navigation system. Compared with the second filter, the convergence speed of Earth oscillation error is obviously faster after information fusion, and the short-term accuracy is significantly improved. Compared with the first filter, the steady-state navigation accuracy is significantly improved after information fusion.

Abstract:Rain weather will affect the quality of the outdoor images and blur and cover the image information. To improve the clarity of outdoor images affected by rain streaks, restore image feature information and improve the accuracy of many computer vision algorithms under rain weather condition, a single image rain streaks removal method based on the multi-scale convolutional neural network is proposed. Firstly, the structure of the multi-scale convolutional neural network is established and the method extracts information of images by multi-scale convolution. The information is utilized to remove the rain streaks and reconstruct images. Then, the method combines the features of rain which include low saturation and high intensity to train the network. The optimal parameters can be obtained in this way. Finally the convolutional neural network can remove the rain streaks in single images effectively. Experimental results show that the proposed method compared with the existing methods has better performance about rain streaks removal. It can better maintain the original information of the image and avoid blurring of the image. Meanwhile, using multiscale convolution to extract feature information can enrich the feature information and it is beneficial to improve the rain removal ability of the convolution neural network.

Abstract:To solve the problem of performance evaluation and improvement when the Spark tasks are performed, this paper proposes a Spark performance evaluation and an analysis method based on the heuristic algorithm and support vector machine regression model. A heuristic performance evaluation algorithm is proposed, which uses Ganglia to collect and process the consumption data of cluster resource when performing the Spark tasks. According to the k-means algorithm, the task type is determined and the evaluation index and the initial weight of the heuristic performance evaluation algorithm are determined according to the task type. The task efficiency data is collected and processed from the Spark history server, and it is regarded as the state data of the Spark run-time task along with the cluster resource consumption data. The final weight of the heuristic performance evaluation algorithm is determined according to the state data iteration process, and then the Spark Performance Evaluation Regression Model is established. A Spark performance analysis method based on support vector machine SVM regression algorithm (SVR) is proposed subsequently. This method establishes a regression model for the Spark configuration parameter and the overall performance, and then analyzes the sensitivity of the regression model to find important parameters that affect the performance of Spark. The experimental results show that the heuristic performance evaluation algorithm can quantify the performance of Spark task resource consumption and operation efficiency, and can comprehensively evaluate the overall performance of the task. The SVR-based performance analysis method can be applied to the actual analysis of Spark task effectively, which can form the initial tuning advice about the Spark mission performance.