Reflective crack is one of the primary pavement distresses leading to the failure of composite pavement. To study the fatigue life of asphalt overlay controlled by reflective crack induced by large aircraft, composite stress intensity factor was firstly taken as the mechanical index to establish the fatigue life prediction model of the asphalt overlay based on propagation law of reflective crack. The distribution of stress on the asphalt overlay under the critical locations of gear loads with different interface conditions was then simulated by finite element method.
Then, the regular pattern of the composite stress intensity factor was also obtained and applied to establish a formula between the fatigue life and the mechanical & geometrical parameters of different overlay structures. Finally, the formula was applied to optimize the asphalt overlay structure of the runway in a civil hub airport and the result turned out to be 6 cm SMA(stone mastic asphalt) + 9 cm AC(asphalt concrete).
Airport terminal is a large public building, it can easily cause smoke accumulation and make evacuation difficult once a fire occurs. Traditional fire fighting facilities are difficult to meet the fire fighting needs of such buildings.
In this paper, the evolution mechanism of coupled fire facilities is studied. Firstly, the building information modeling (BIM) of terminal hall is established, and the fire simulation of terminal in different scenarios is carried out through fire dynamics simulator (FDS). Then the data of sprinkler operation, smoke layer height, visibility and heat release rate in different regions and different scenarios are obtained. The fire evolution mechanism is analyzed according to the changing process. The results show that there is a significant difference in the fire evolution mechanism between the coupled fire fighting facilities and the non-start-up fire fighting facilities for the special public building such as airport terminal. At the same time, the simulation results can provide ideas for the optimization of fire fighting design and the formulation of emergency evacuation plan of airport terminal.
Aiming at the problem that the existing deep neural network based code defect detection methods cannot analyze the defect characteristics and output relevant review suggestions, a code defect detection method based on LSTM-Seq2Seq model with large perception is proposed. Firstly, the long short-term memory network (LSTM) is applied to obtain the coding characteristics of defective code and establish a defect identification model.
Secondly, aiming at the mismatch between model and dataset, the code segment length coefficient is introduced into the sequence to sequence (Seq2Seq) model to improve the model applicability to the code review task. To realize the review output function, the code analysis model is constructed by establishing the mapping relationship between the features of code defect and the review recommendation. Finally, the method is verified by the open data set of SARD. The results show that the accuracy rate, recall rate and F1 vale of the proposed method are 92.50%, 87.20% and 87.60% respectively, and the similarity between the output review of typical code defect and the expert review is 85.99%, which can effectively reduce the dependence on expert experience in the review process
Aiming at the gate assignment problem that there was large time execution deviation in actual operation, the feasibility that reduce time execution deviation using total airspace and airport modeller (TAAM) was discussed.
A model was established with the boarding time of passengers, unbalanced gate occupation, and balance of average taxiing distance of airlines as targets. First, TAAM tool was used to simulate and optimize scheduled gate operation time, and got initial solution of gate assignment. And then entropy-weight method was applied to transform multi-objective into single objective problem. Finally, Tabu algorithm was used to solve the proposed model. The simulation results of verifying the time execution deviation before and after the optimization of gate operation showed that after the optimization, time execution deviation was significantly improved, and the efficiency of gate operation was effectively increased.
A flight simulation system was designed taking an unmanned helicopter as the simulation object, which consisted of four parts: flight simulation module, cockpit simulation module, visual simulation module and console module.
The flight simulation module built the dynamic models of rotor, tail rotor, fuselage, horizontal tail and vertical tail, and the Simulink module was written by S function. The photo-level flight instrument was designed by GL Studio software for real-time display of flight data. The visual simulation module was redeveloped based on Vega Prime simulation platform. The basic simulation framework was built and the console interface was designed by multithread method based on MFC (microsoft foundation classes), which was used for real-time interaction with users.
Finally, the feasibility of the system was verified by simulation.
The D2 navigation data broadcast by the BeiDou geostationary earth orbit (GEO) satellite may change every 2 ms.In weak signal environment, the usual acquisition algorithm cannot effectively capture the signal. To solve this problem, a weak signal acquisition method based on navigation data estimation is proposed. The capture strategy of this method can be adjusted according to the signal quality, by quickly and accurately estimating the navigation data, thus the impact of navigation data jump on capture sensitivity is reduced. The simulation results show that, for the BeiDou GEO signal with length of 60 ms and signal-to-noise ratio of -34 dB, the acquisition success rate of this method is 80%, and the acquisition time is equivalent to that of the full-bit method.
To identify the prone airspace of complex terrain-induced low-level windshear at Hong Kong International Air port(HKIA), large eddy simulation(LES) method was used to simulate the wind field of the airport and its surrounding terrain. The wind speed changes at the take off and landing paths of three runways under the background of east, southeast, south and southwest wind were compared combined with wind speed cloud map, and the causal relationship between the terrain and the wind field distribution was analyzed. By comparing the results with the control test without terrain, the F-factor (headwind) and 7-knot standard (crosswind) were employed to identify the prone regions of low-level windshear at the airport runway. The results showed that the east wind was easy to cause the temporal and spatial variation of the headwind speed at the take off and landing paths of the aircraft.
The southwest wind affected the headwind speed at the landing path on the east side of the runway, but had little effect on the take-off path on the west side of the runway. Under the background of southeast wind and the south wind, the crosswind in the low altitude section at the approach-departure paths of the three runways were signifi cantly affected by the terrain. According to prone airspace of the low-level windshear at take off and landing paths of three runways, the influence range of topographic factors on low-level windshear of HKIA was obtained, which can provide active avoidance measures and suggestions for airport windshear risk prevention and control.
