A field survey is conducted to explore the distribution characteristics of through vehicles' trajectories with and without protected left?turn phase at three cross sections under non?strict priority. A driver′s decision process is presented to avoid opposing left?turning vehicles with respect to operational performance. Then the trajectory model of through vehicle with an unprotected left?turn phase is proposed considering three constraints: intersection geometry, velocity of a through vehicle when entering an intersection, and the minimum safe distance between a through vehicle and an opposing left?turning vehicle. At last, the model is validated by actually measured data. The study can provide a better understanding of crossing through maneuver with an unprotected left?turn phase under non?strict priority, and offer the theoretical basis for microscopic traffic simulation.

Pedestrian tracking is the base for pedestrian behavior analysis and driving decision?making. There exist several problems such as the fast scale change of pedestrian caused by rapid movement of vehicle, the pedestrian occlusion, etc, which make the traditional tracking algorithm difficult to track pedestrians accurately, and it is more difficult to analyze pedestrian movement. To overcome the problems, a new pedestrian tracking method is presented in the paper. In the method, scale estimation and selective updating strategy were used to deal with fast scale change of pedestrian and occluded in the framework of background?aware correlation filter. First, a background?aware correlation filter was trained online for the pedestrian to be tracked. Secondl an one?dimensional scale correlation filter was trained to search the scale of pedestrians carefully, so that the algorithm is more adaptable to fast scale change in the case of vehicle driving. Finally, a selective updating mechanism of the correlation filters was set up by using the peak sidelobe ratio to evaluate the pedestrian status. In experiments, the proposed method was compared with Kalman filter pedestrian tracking algorithm on JLU?PDS, Daimler Pedestrian Benchmark Data Set and some video sequences from Object Tracking Benchmark. The results show that the proposed method has better scale adaptation and anti occlusion performance, and it is more adaptable to the autonomous driving.

To make pedestrians flow simulation model more comprehensive, and explore the effects of slipstreaming behavior on pedestrians crossing, a modified social force model is proposed to investigate pedestrians crossing process considering the slipstreaming behavior and conflict avoidance at signalized intersections. In the modified model, slipstreaming model, physical forces acting on pedestrians by signal control and crosswalk boundaries and conflict avoidance force are combined to simulate pedestrians at crosswalk. Based on the simulation results, the variations of crossing speed and potential accidents were analyzed. It is found that slipstreaming behavior can increase the crossing speed and reduce crossing time of bidirectional pedestrians; the conflict avoidance force can efficiently reduce potential accidents.

In heterogeneous traffic conditions, the designs of signal timings were based on motor traffic flows in most traditional signal control methods, which may reduce the motor vehicles′ operating efficiencies and hinder the traffic engineers from finding the optimal signal timings. Therefore, a traffic signal actuated control method for heterogeneous traffic was proposed, which targets on motor and non?motorized vehicle traffic flows at isolated intersections. This method combined an optimization algorithm and an actuated control logic. The basic green time of each phase was optimized according to the real?time data obtained from the heat?imaging traffic detectors. Then, the initial green time and the maximum green time of each phase, the key parameters of the actuated control, were formulated as the expansions of the basic green time. The method was evaluated using field data, and the rationality analysis shows that the non?motorized vehicles in heterogeneous traffic have an influence on the traffic flows. In addition, an offline verification was designed, and the results show that the average vehicle delay is reduced by 7.69% when considering the non?motor vehicles in the optimization algorithm, while the proportion of oversaturated cycles is decreased by 80.77% under the actuated control.

Considering the limitation of insufficient accuracy and poor stability of multi?sensor traffic data fusion algorithm, a mind evolutionary data fusion algorithm based on BP neural network is presented. Based on the introduction of the basic principle, the calculation steps of the proposed fusion algorithm for optimizing the initial weight and threshold of network are designed by using the “convergence” and “alienation” operations. This makes it possible to find out the best fusion model. The empirical analysis using the interval velocity indicates that the proposed fusion algorithm shows better convergence and has better accuracy and stability than the BP neural network algorithm, which are improved by 9.38% and 31.44% respectively. Time sensitivity analysis shows that the proposed fusion algorithm also has good transportability.

In order to examine the influence of built environment and parking availability on commuting mode choice, the integrated path analysis?discrete choice model (PAM?DCM) is proposed. In this model the car ownership and commuting distance are considered as the mediating variables. The data from Changchun household travel survey is used to estimate model parameters using Mplus software. The results indicate that the model considering parking availability performs better than the model ignoring the parking availability. Also, the influence of parking availability on car use for commuting is significantly positive. Meanwhile, built environment in residence and workplace has significant effects on car use for commuting. Moreover, it is found that the influence of residential built environment is greater than that in workplace.

Due to the uncertainty in transportation system, the travel time of paths varies within a certain range. For stochastic transportation network, travelers have different risk attitudes which can be divided into three categories including risk?averse, risk?neutral and risk?seeking attitudes. The normal distribution was used to describe the randomness of travel time of links, and models of travel time budget, mean?extra travel time and mean?below travel time were considered to study travelers′ path selection behavior, in addition, travelers with multi?Point of Interests (POIs) were also considered. A label?correcting algorithm was proposed to solve this problem, setting α=0.75 and α=0.25 respectively. The results of shortest path selection of travelers with different risk attitudes were analyzed. The computational performance of the algorithm was tested in different scale of networks. The results show that the average operation time of the label?correcting algorithm is about 100 ms in the network with 10 000 nodes, which is about 42% slower than the classic algorithm of dijkstra in the deterministic network. Comparative analysis shows that the algorithm is fast and can meet the requirements of practical application.

Unstructured roads usually do not have leading lines such as lanes, and the road boundary is vague and there exist many interference factors around the roads. Therefore it is not reliable to use the lane keeping system for autopilot and driver assistance system in this kind of roads. By generating the entropy image from original image the minimum difference of histogram of the entropy image is computed, and the difference is used as the segmental threshold to preliminarily segment the image. Then, the improved region growing method is used to extract the lane from the preliminarily segmented image. The real?time quadratic curve is used to establish the lane model, and the improved least square fitting method is applied to effectively avoid noisy points on the edges of lane region and promote the fitting speed. The experimental results show that the improved methods can be used to rapidly extract the lane from road image and fit out the lane line, therefore it helps to achieve visual based lane keeping on unstructured road for autopilot and driver assistance system.

In order to solve the problem of highway traffic safety in the mountainous area, vehicle transient aerodynamic feature and its laws in bridge and tunnel connecting segment affected by the wind environment are studied. With the help of Carsim software, the vehicle model and the road model are built to simulate the feature of the vehicle and road in bridge and tunnel connecting segment. The measured varying wind speed of Xihan Expressway is input to simulate the average wind and fluctuating wind of the natural wind load, and the influence of wind angle on the vehicles is researched. Firstly, after simulation, the parameters, such as vehicle longitudinal speed, lateral acceleration, aerodynamic force(drag force, side force and lift force) and aerodynamic slip angle are analyzed. Then, the influences of the vehicle aerodynamic forces of different vehicle speeds, wind speeds and wind directions on the driving stability are analyzed. Finally, the critical vehicle speed and critical wind speed of safe and stable driving in the side wind environment are investigated. Research results show that, when the vehicle speed is increased from 60 km/h to 80 km/h, the drag force, side force and lift force are increased by 160%, 53% and 89% respectively. Under the snow and ice surface with wind speed of 80km/h, a large offset of more than one meter occurs. When the maximum wind speed of Xihan Expressway was 31.5 m/s (about 113 km/h), the vehicle will obviously overturn and it will be a risk to driving safety.

A significant approach to save energy of the middle?to?high speed maglev is to optimize the trajectory planning. This paper establishes a model based on dynamic programming with mutative spacing after analyzing the kinetic equations of the middle?to?high speed maglev and the effect of the assistant?stop area. The model firstly uses the crossover point of double protected curve as the foundation of partition. Then, model further divides the partition into small sub?stages with different spacing and formulates the equation of energy and time respectively. Finally, the model is solved by reversing push method under certain constraints. The established model is compared the conventional dynamic programming method through the numerical examples. The results indicate the advantage of the proposed model in energy saving and computational efficiency.

To investigate vehicle braking performance on wet asphalt pavement, a method was developed to simulate the vehicle braking process on rainy days considering rubber?pavement friction and water film hydrodynamic force. Firstly, the pavement surface fractal friction theory was applied to calculate the rubber?pavement kinetic friction coefficient based on pavement surface power spectrum and rubber complex modulus. Secondly, a finite element tire hydroplaning model was constructed to determine the tire?water film?pavement interaction force with different vehicle velocity and water film thickness. Based on these, a full vehicle dynamic model was constructed to evaluate the vehicle braking performance on wet straight road and curved road, and vehicle anti?lock braking mechanism was analyzed. Research results show that the rubber?pavement kinetic friction coefficient declines by 13%~34% when pavement becomes wet. In the tire hydroplaning process, tire-pavement contact force rises and water uplifting force drops with the increase in vehicle velocity and water film thickness. The lower vehicle velocity, the smaller water film thickness and the equipment of anti-lock braking system are useful in reducing vehicle braking distance. Compared with critical tire hydroplaning speed, the full vehicle model is superior in coinciding with the actual situation in evaluating vehicle driving performance on wet pavement.

In order to reveal the variation law of the macro?mechanics properties of the subgrade soil from the mineral composition and the mineral content level, the primary and secondary chemical component measurements of the different plastic index subgrade soils were carried out. The rock mineral composition and clay mineral relative content are determined. Based on the gray relational theory, the correlation between the mineral content and the shear strength and cohesion and the internal friction angle were analyzed. The results show that among the chemical components, FeO, K₂O and SiO₂ have greatest relational degree with soil shear strength, and the relational degree is greater than 0.9; P₂O₅ has the greatest relational degree with the cohesion, it is greater than 0.85; Na₂O, SiO₂, K₂O, FeO have greatest relational degree with the internal friction angle, relational degree of Na₂O, SiO₂ is greater than 0.9, and relational degree of K₂O, FeO is greater than 0.8. According to the mineral composition of the whole rock, f_s and Q have great relational degree with the shear strength, the cohesion and the internal friction angle. The relational degree is greater than 0.9. While Pl has little relation degree with the macro?mechanics properties, and its effect on shear strength and parameters can be ignored. According to relative content of clay minerals, I/S has the greatest relation degree with the shear strength and cohesion and the internal friction angle. Whereas I has greater relation degree with soil cohesion. K has little relation degree with the shear strength and parameters, so it can be ignored when soil macro?mechanics properties are analyzed.

To solve the problem of excessive number of sensors and to optimize the measuring points in damage assessment of bridge structures, a method of multi?stage subregion mobile test was presented based on the displacement coordination condition of continuum and state stochastic space theory. This method can be used to identify the mode shape of overall structure by sub?region.The diagnosis method based on modal flexibility coefficient for angle element as damage index is proposed. The analysis results show that the new approach can exactly and efficiently obtain complete structural dynamic response data with less equipment conditions, and gain more precise outcome.

To study the influence of uneven settlement on the structure of inclined shaft segment caused by the drainage of overlying water?bearing sandstone after coal mining, a similar simulation test was carried out on the area where inclined shaft crossed the boundary between coarse?grained sandstone and sandy mudstone. The settlement rule of water?bearing sandstone and longitudinal and hoop stress?strain distribution of inclined shaft segment was simulated by model test in different formation pressure, pore pressure and drainage rate. The distribution rule and influencing factors of additional stress in the inclined shaft segment were analysed. At the same time, according to the model test, the influence of additional stress, surrounding rock pressure and pore?water pressure caused by uneven settlement on the inclined shaft segment was put forward.

To investigate the characteristics of Linear Generator/Engine System, the numerical simulation model of the system was set up. The accuracy of the simulation model was validated by a prototype. The disturbance during stable operation of the system was analyzed. under the extreme conditions of misfire, knocking and large variable load, an integrated control strategy was proposed based on mid?point velocity detection and trajectory tracking. The electromagnetic force control was applied during the whole stroke, and ignition control was applied around the top dead center. Results show that the system can return to stable operation within three strokes under this control after disturbance happens.

In view of EGR performance evaluation of turbocharged diesel engine, especially the optimal EGR rate under ‘small sample’, an optimization evaluation and decision?making method is proposed. First, the major test parameters including in?cylinder burst pressure, fuel consumption rate, NO_x, CO and smoke are selected based onTBD234V12 type turbocharged diesel engine with a high?pressure exhaust gas recirculation system to establish the optimal correlation analysis model for the preliminary evaluation of different EGR schemes. Second, according to different speed conditions of diesel engine, a comprehensive evaluation model is established using optimized objective evaluation method. Finally, a simulation optimization platform for comprehensive performance evaluation and optimal decision?making of EGR is designed and established using MATLAB GUIDE. The results show that When diesel engine is in low?speed conditions, low EGR rate corresponds to a higher comprehensive assessment value, so a smaller EGR rate should be adopted. When diesel engine is in high?speed conditions, the comprehensive assessment value corresponding to the lower EGR rate is lower, and the higher EGR rate obtains a higher assessment value. However, the evaluation value of overly high EGR rate decreases. This result is basically consistent with the current control principle of EGR; The simulation optimization platform can quickly and easily solve the EGR performance evaluation and optimal decision?making of turbocharged diesel engine.

The correlation between metal surface morphology and metal?plastic direct adhesion strength was studied. First, the oxide film on the metal surface was removed by acid and alkali solution. Then, the metal surface was treated by fiber laser, and the hot pressing connection between metal and plastic was completed by plate vulcanizing machine. Third, the effects of different laser power and different scanning density on the direct bonding strength of metal?plastic were investigated. Finally, the correlation between the surface characteristics of metals and the direct connection strength of metal?plastic direct adhesion was analyzed based on the microstructure morphology and Scanning electron microscope (SEM). The results show that the direct connection strength of metal?plastic increases first and then decreases with the increase in laser power. With the increase in scanning density, the strength of direct connection between metal?plastic increases.

In order to study the effect of hygrothermal environment on the tensile properties of Sikaflex?265 adhesive for vehicle, the tensile failure strength of Sikaflex?265 adhesive was obtained under the quasi?static tensile test of aluminum alloy butt joint in 20 kinds of hygrothermal environment. With Matlab software, the test data were fitted by quadratic polynomial function and exponential function. The quadratic polynomial function was found to be more accurate to reflect the variation trend of Sikaflex?265 adhesive tensile failure strength with temperature and humidity. With Matlab software, regression analysis was made to establish the prediction model of Sikaflex?265 adhesive tensile failure strength under arbitrary hygrothermal conditions. Comparison with the experimental result shows that the proposed model has good prediction precision.

Continuum Damage Mechanics (CDM) was introduced into the finite element analysis of scratch resistance of coatings. Firstly, a damage mechanics based on the material model was created. Secondly, this material model was implemented into ABAQUS solver through user defined subroutine VUMAT. Finally, a series of analyses were carried out to analyze the mechanical behavior of coatings. The material model could be used not only to capture the stress distribution of coatings, but also to predict the damage evolution of coatings under scratch loading. In addition, it is found that the loading speed and coating thickness have certain effects on scratch resistance, but the properties and thickness of substrate have little effect on it. The theoretical support was provided for the optimal design of the coating material.

In this paper, the thermal cycle curves of different processes of 4 mm 6082?T6 aluminum alloy bobbin?tool friction stir welding were detected using thermocouples measurement technology. Then the distribution characteristics of temperature field in the test area were analyzed. The results show that the maximum temperature of each measuring points at the retreating side of the welding is always higher than the advancing side, and the maximum temperature difference is about 20 ℃. When the HAZ temperature exceeds 250 ℃, the β'' begins to dissolve and the hardness begins to decrease. When the welding speed is constant, the heat input increases first and then decreases with the increase in the spindle speed. At 1000 r/min, the measuring point reaches the maximum temperature value, and then decreases at 1200 r/min. When the spindle speed is constant and the welding speed increases, the heat input of unit time decreases，and the difference of peak temperature increases between the advancing side and retreating side, the width of 250 ℃ isotherm is reduced considerably.

To solve the problem of the poor corrosion resistance of 6061?T6 aluminum alloy under various extreme working condition, experiments for 6061?T6 aluminum alloy were carried out using laser shock peening with different coverage layers. Then the effect of laser shock peening on the corrosion resistance of 6061?t6 aluminum alloy was analyzed by measuring the residual stress and surface roughness, observing the microstructure and electrochemical corrosion test. The results suggest that the residual stress and surface hardness increase with the increase of the laser shock coverage layer. The alloy grains are refined obviously in the impacting area, and the scale of grain refinement layer extends with the increase of laser shock coverage layer. The surface roughness decreases with the increase of laser shock coverage layer. After laser shock peening, the corrosion resistance of 6061?T6 aluminum alloy is obviously improved, the electro?chemical corrosion current decreases and the impedance radius increases, the growth of surface pitting pits is obviously inhibited. The combining effects of increased residual stress, microstructure refinement and decreased surface roughness improve the corrosion resistance of 6061?T6 aluminum alloy.

Effects of Laser Shock Peening (LSP) with different coverage layers on Corrosion Fatigue (CF) resistance of 2Cr13 stainless steel were investigated by residual stress measuring, CF testing and fatigue fracture morphology observing. The results show that LSP can induce high compressive residual stress on the surface of 2Cr13 stainless steel, and the value of surface compressive residual stress increases with the LSP coverage layer. The CF life of LSP specimens is much larger than that of as?machined specimens, and it increases with the LSP coverage layers. The CF crack growth rate of LSP specimens decreases compared with that of as?machined specimens, and it decreases with the LSP coverage layers. After the analysis, we can conclude that the fatigue fracture surface of as?machined specimens is flat and contains few secondary cracks. However, for LSP specimens, due to high surface compressive residual stress induced by laser shock peening, the growth of CF crack is effectively restrained, resulting in a river pattern morphology.

The tensile properties of 45 steel after reciprocating torsion are tested by self?made in?situ tension?torsion?nanoindentation mechanical testing device.In this study, the mechanical properties curve of 45 steel after reciprocating torsion and the changes of its elastic modulus, hardness, yield strength and strain hardening exponent are obtained by Nano indentation test. The feasibility of calculating the mechanical properties of 45 steel by Nano indentation test is confirmed by in?situ tensile test. The mechanical parameters obtained by tensile test and indentation test are in good agreement. The damage mechanism of materials under reciprocating torsional loads is further analyzed by in?situ images, and the correctness of the experimental results is confirmed. The experimental basis is provided for obtaining the mechanical properties of materials by nanoindentation test in service.

In order to investigate the inherent link between the linear compressibility properties and the geometrical parameters, the 3D hinging octahedron structure was analyzed by a finite element method. With constant geometry size, different finite element models were established by changing the rod length ratio of l₁/l₂ and angle θ₁ between the two rods. The effects of these two structure parameters on the magnitude as well as the range of negative linear compressibility (i.e. NLC) of this structure were analyzed and discussed. It is shown that through carefully choosing the geometry parameters, NLC can be exhibited in this model along the three?axis directions. More specifically, the sign of the linear compressibility is determined by the angle θ₁ while the magnitude and range of NLC are determined by the l₁/l₂ ratio.

A multi?functional auxiliary station type wheelchair mechanical structure is designed. Through the linear linkage design of variable rod length and variable rod position, the functions of supporting rod type seat lifting inside and outside the system and assistant sitting down in waiting mode are realized. The vertical displacement of external support rod fixed point is accurately controlled by adding an armrest device, so that the mechanism can assist the patient to fit the normal standing track of healthy human body in the course of operation for sitting down and standing down. The standard healthy human body station and sitting trajectory were normalized after normalization in Matlab software. The structure simulation using Catia software shows that the structure can complete the effect of sitting?assisted motion of the healthy human body. The function of automatic toilet movement or wheelchair movement can be realized by adding the toilet seat and moving wheel. Using finite element software, the minimum quality is the goal, the constraints are set, and the quality of the consumables is greatly reduced under the premise of ensuring the mechanical properties of the mechanical structure.

An actuator based on the structure of servo motor and rack and pinion is designed. The two components of actuator damping force are analyzed theoretically, which are mechanical friction damping force and inertia force, and their calculation methods are given respectively. Compared with the traditional passive damping force, the influence of the inertial mass on the damping characteristics of the actuator is analyzed through typical sinusoidal excitation, and further verified by bench test. The test results show that the calculation method of damping force is reasonable, can match the actual damping force of the actuator well. However, it is also found that the inertial mass of the actuator results in the rise of the maximum damping force and the nonlinear characteristic which goes against its active control. Moreover, the idle stroke of the structure leads to obvious fluctuation of the damping force in the process of high frequency reversing. So, in the process of actuator structure design, it should be considered to reduce the inertial mass and idle stroke by optimal design.

A numerical model was developed to investigate the mixed lubrication performance of herringbone grooved journal bearing when axial reciprocating motion and journal misalignment were considered. The oil film pressure considering the roughness effect can be obtained by transient average Reynolds equation. The elastic deformation can be obtained through influence function method, and the contact pressure can be simulated by Lee?Ren asperity contact model. The variation of oil?film force, contact load ratio, and friction coefficient with time were investigated by numerical simulation, and the effect of axial movement amplitude and misalignment angle on mixed lubrication performance were also studied. The research suggests that the oil?film force is corresponding over axial velocity, and the contact pressure shows inverse variation with axial velocity. Besides, the increase of axial movement amplitude in negative movement state will result in a significant reduction in load capacity and lubrication performance of journal bearing. The research also shows that the load capacity and lubrication performance of journal bearing decrease with the increase in misalignment angle.

The clamshell was used as the research object, and three types of clamshells under different water conditions were carried out by mechanical testing machine,including of the fresh, soaked and dry shells.Based on the experimental data of bearing pressure and the crack characteristics and microstructure of shell, the whole bearing pressure characteristics and fracture law of clamshell surface were analyzed. The results showed that the pressure performance of the shell surface is the best in the fresh body. The mechanical properties in soaked bodies decreased because of the loss of the organic matter after the soaking. The compression capacity declined sharply when the shell was dry.The reason was that the water lost in the shell body and the organic matter dried up. the shell crack propagation and shell crack change were different in the three states. This study will provide important reference value for the study of mechanical properties and biomimetic application of shell surfaces.

To reduce the interaction force and power consumption between the blade and soil in the grassland, and also to optimize the matching relationship between the rotation speed of the forward speed, the study investigated the effect of five velocity ratio(the ratio of the line velocity of the blade point to the forward speed) of five levels(16.9、20.7、24.5、28.2、32.0) on the torque, specific work(power consumption per volume), and the total power though the soil bin test. At each velocity ratio, there were three different combines of the forward speed (0.5, 1, 1.4 m/s) and different rotation speed calculated by the ratio and the forward speed. The results showed that the torque coefficient of variation were just 2.4%, 5.2%, 1.7%, 7.5%, 3.9% respectively, the specific work coefficient of variation were just 1.0%, 3.4%, 8.8%, 2.7%, 2.7% respectively when the velocity ratio was constant, demonstrating that the torque and the specific work were independent of the combines of the forward speed and the rotation speed, it was just determined by the velocity ratio. So the relationship between the velocity ratio and the torque, the relationship between the velocity ratio and the specific work, and the relationship among the total power, the rotary speed, and the velocity ratio were built. What’s more, to explain the relationships above, the relationship between the torque and the bite length, and the relationship between the specific work and the bite length were built. According to the relationships built above, the minimum torque was 90.79 Nm when the velocity ratio was 27.41, the minimum specific work was 6369 kJ/m³ when the velocity ratio was 26.31, the total power was 2362 W when the velocity ratio was 28 and the lowest rotation speed was 200 r·min^－1. When the value of the velocity ratio was around 26.31 at which the specific work was minimal, the torque and the total power were both close to the minimum(with the difference of 1.2% and 4.2% from the minimum respectively), so that value was the most suitable velocity ratio for root?cutting in the grassland.

In order to alleviate the false positive problem in distant supervision for relation extraction and improve the precision and recall rate, this paper presents a distant supervision model with weak constraints of entity pairs for relation extraction. This approach first gains constraint information of entity pairs from knowledge base and plain text, which contains key words of entity pairs and entity types. Then the model can obtain features of constraint information automatically by training neural networks. Then these features are used as weak constraints during relation prediction in company with the features of sentences. In contrast experiments, the model with weak constraints of entity pairs achieves higher precision and recall rate. Results show that weak constraints of entity pairs can effectively alleviate the false positive problem and enhance relation extraction.

With the rapid growth of the location?based social networks, Point of Interest (POI) recommen?dation has become an important research topic in the field of data mining. Existing approaches for POI recommendation task do not reasonably utilize the time sensitivity of POI recommendations and have not taken full account of the user's behavior preferences at different time periods, causing the POI recommendation performance is poor. Firstly, this paper studies the POI recommendation problem of time sensitivity and proposes a time dynamic partition algorithm based on hierarchical clustering. Through partition the fine grain of time, the result of the experiment is more reasonable and effective than the previous experiments which partition time is evenly given by experience. Secondly, by combining the time?aware recommendation with the influence of the user's direct friendship and potential friendship, the paper expands the scope of user's social influence, and then further improves the POI recommendation performance. Lastly, using the method of randomly selecting POIs by the frequency distribution of check?ins, it improves the classic BPR method. Experimental results on the two datasets indicate that the TPR?TF model is superior to the current mainstream POI recommendation models, in terms of precision and recall.

In order to improve the handling stability of active four?wheel steering vehicle based on the Steer by Wire technology, a nonlinear triple?step method is adopted to the linear active four?wheel steering systems so as to track the output of the ideal reference model. The proposed scheme consists of three parts: steady?state?like control, feedforward control considering the variation of the reference signal, and state?dependent error feedback control. The method guarantees that the actual sideslip angle and yaw rate can track the ideal sideslip angle and the ideal yaw rate by the control of the front wheel angle and rear wheel angle of active four wheel systems. A nonlinear eight DOF vehicle model is used to verify the effectiveness of the proposed scheme. Simulation results show that the designed controller can track the output of ideal reference model and improve the handling stability of the active four?wheel steering system.

For the purpose of reproducing human mandibular movement, and improving the bio?imitability of masticatory robot, a redundantly actuated parallel masticatory robot with point contact Higher Kinematic Pair (HKP) is introduced. The medical measurement method for analysis of Temporomandibular Joint (TMJ) structure is utilized and the bionic design of point contact higher kinematic pair of the masticatory robot is achieved. The bilateral correlated movement of the TMJ is analyzed and kinematic model is established based on the higher kinematic pair constraints. The trajectories, maximum velocities, frequencies of mandibular opening?closing movement are obtained by measuring several experimental subjects. The opening?closing movement experiment and force experiment are carried out on the masticatory robot prototype. The results show that the robot is able to achieve functionality of mandible movements and chewing forces which are required by denture wear fatigue behavior analysis.

In?situ observation of hadal fish has been widely implemented for scientific research, usually on serial time or fixed time interval observation mode. However, the observation efficiency is extremely low since pre?programmed method cannot perceive the interested targets in camera view. A novel autonomous observation method combined with computer vision technology is proposed, where observation strategy could be dynamically adjusted according to the result of fish recognition. Moving targets are rapidly segmented from video frames based on improved background difference method. Invariant moment, eccentricity and roundness characteristics are extracted subsequently, and Fisher discriminant function is used for feature reduction. Fish target prediction model is then established with PSO?SVM algorism. The effectiveness of proposed autonomous observation method is validated through simulation experiment using in?situ observation video data of hadal trench expedition.

To enhance the search and rescue capacity, this paper represents an optimal algorithm of searching route for large amphibious aircraft to complete its search tasks within minimum time based on the flight characteristics of aircraft. The search route planning problem is transformed into a discrete programming problem considering the indexes of both missing search rate and duplicate search rate. The optimal route planning algorithm applied the route backdate indexes to satisfy the duplicate search rate. Meanwhile, the planned routes satisfy all constraints, such as the maximum overload, no?flying zone and so on. The numerical simulation results indicate that the performance indexes of the optimal routes calculated by the optimal route planning algorithm are better than the ones obtained by the traditional search route planning methods.

In order to effectively solve the star sensor layout problem with higher efficient, the particle swarm optimization algorithm is applied. Firstly, the spherical projection method is utilized to select the points which can effectively avoid the ground light as the particle population. Secondly, the error from angle between the star sensor optical vector and the sun vector to the sun exclusion angle of the star sensor is selected as population evaluation function, and the best layout of the star sensor is found through the particle swarm searching of the global optimal solution. The effectiveness of star sensor layout scheme selected by the proposed method in this paper is proved by the experiments.

Low computational rate and poor performance in real?time signal processing are the main problems for the median filtering algorithm in the practical applications. This paper proposed a high?speed parallel median filtering algorithm based on Graphics Processing Unit (GPU). The algorithm uses Compute Unified Device Architecture (CUDA) to optimize large?scale data processing and it is implemented on NVIDIA GPUs to improved its computational efficiency. The GPU′s dynamic memory space is allocated by constructing GPU?scalable dynamic array and optimization of multidimensional index linearization methods. Experiment results show that, the 5×5 median filtering based on TITAN X GPU is approximately 438x faster than CPU algorithm for processing of 4096×4096 pixel images. The GPU based median filtering can greatly improve the computing performance of algorithm under the same computing conditions.

To solve the problem of source detection in the case that the number of signals is larger than that of physical elements, a new method based on source number estimation of coprime array is proposed. First, the coprime array is used to exploit the degrees of freedom offered by the difference sets. Then, by applying the properties of the coprime array, the unknown parameters are estimated, which are critical to the probability density function of the vectorized outer?product of the array output. Finally, by using the likelihood function and MDL criterion of the parametric probability model, the function of the algorithm is realized. Simulation results show that the proposed method has good performance even at low signal?to?noise ratio when the number of snapshots is large enough.

This paper presents the Nonlinear Frequency Modulation (NLFM)?Costas hybrid signal with the complex methods of interpulse Costas frequency coded modulation and intrapulse Nonlinear Frequency Modulation (NLFM). The signal construction is analyzed in theory and four critical parameters are obtained, such as Power Spectrum Density (PSD), ambiguity function, Peak Sidelobe Level (PSL) and Integral Sidelobe Level (ISL). The experimental results show that the NLFM?Costas hybrid signal has the “thumbtack” ambiguity function and better autocorrelation property. The NLFM?Costas signal can achieve better RF stealth performance than NLFM signal or Costas signal or LFM?Costas hybrid signal and it has good application prospects in modern battlefield environment.

Aiming at the complex electromagnetic environment in modern battlefield, the accuracy of traditional radar modulation signal recognition method based on conventional five?parameter feature is low under low signal?to?noise ratio (-6 dB). In this paper, AlexNet convolution neural network model in deep learning is used to automatically extract various feature details of image, which can replace the huge Feature Engineering designed by hand to realize signal recognition under low signal?to?noise ratio. Firstly, the time?frequency image of radar modulation signal is generated by smoothing pseudo?Wigner?Ville time?frequency analysis in time?frequency domain; then, the time?frequency image is preprocessed by median and mean filtering combined with denoising; finally, the AlexNet model is trained by using image processor GPU under the deep learning framework Tensor flow, and CW, LFM, E are trained. Seven kinds of radar signals, QFM, DLFM, BFSK, BPSK and QPSK, are automatically extracted and selected to realize automatic recognition of radar signals. The simulation results show that the overall recognition rate of the other six radar signals, except QPSK signal, is more than 90% at the signal?to?noise ratio -6 dB, which is better than that of the non?deep learning and LeNet5 convolution neural network, thus verifying the validity of the method for radar signal recognition at low signal?to?noise ratio.

Fast equivalent cable bundle model is an approximate to traditional equivalent cable bundle method (ECBM), which the electromagnetic behavior of the cable bundle can be equivalent to only one cable if observed from a certain distance away. Compared with ECBM, cable grouping process is greatly simplified therefore could further save computation time and memory. In this paper, the effectiveness of fast equivalent method in full wave analysis is further investigated, and then the fast method is applied to vehicle cables to test its applicability using CST software. The influence of conductivity of ground plane and the height of irregular ground are considered according to real applications under high intensity electromagnetic pulse illumination. Finally the fast method is applied to typical locations of vehicle model and fairly good equivalent precision are achieved to show its practicability.