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In this paper, a data-driven framework aimed at investigating how weather factors affect the spatio-temporal patterns of air traffic flow in the terminal maneuvering area (TMA) is presented. The framework mainly consists of three core modules, namely, trajectory structure characterization, flow pattern recognition, and association rule mining. To fully characterize trajectory structure, abnormal trajectories and typical operations are sequentially extracted based on a deep autoencoder network with two specially designed loss functions. Then, using these extracted elements as basic components to further construct and cluster per-hour-level descriptions of airspace structure, the spatio-temporal patterns of air traffic flow can be recognized. Finally, the association rule mining technique is applied to find sets of weather factors that often appear together with each flow pattern. Experimental analysis is demonstrated on two months of arrival flight trajectories at Hong Kong International Airport (HKIA). The results clearly show that the proposed framework effectively captures spatial anomalies, fine-grained trajectory structures, and representative flow patterns. More importantly, it also reveals that those flow patterns with non-conforming behaviors result from complex interactions of various weather factors. The findings provide valuable insights into the causal relationships between weather factors and changes in flow patterns, greatly enhancing the situational awareness of TMA.

A series of experiments were performed aiming at controlling milling force-induced surface errors in the robot-assisted milling process, for the sub-area of the multi-stiffener reinforced inner wall of complex cylindrical thin-walled casting parts, to investigate the relationship between surface errors, milling forces, and robot-assisted milling parameters. Firstly, based on the design of experiments (DoE) method, milling forces and surface errors were investigated based on a series of experiments with different groups of milling parameters. Secondly, the modeling of milling forces, surface errors, and milling parameters was realized by means of response surface methodology (RSM), then the parametric expression was obtained of the robot-assisted milling process. Finally, the parameters of the milling process toward the surface error were obtained based on an evolutionary algorithm. The results show that the surface errors are different for the different milling styles of down milling and up milling. In up milling processes, the surface errors are positive, and the actual material removal amounts are generally higher than the nominal ones, while negative in down milling processes. The surface errors induced by milling forces can be effectively controlled and reduced using process optimization in the robot-assisted milling process, while maintaining relatively high milling forces and high machining efficiency. This provides theoretical support for industry applications.

In this paper, the stress relaxation behavior of Q235 with the initial tensile stress of 70, 85 and 100 MPa were investigated at different temperature. Based on the thermal activation theory, the stress relaxation model of Q235 steel was established, and the physical mechanism and deformation process in the stress relaxation process were revealed. The results shows that with the increase of temperature or initial stress, the nominal activation volume decreases, but the strain rate and the strain rate sensitivity coefficient increase. The repeated stress relaxation test shows that the stress release amount decreases with the increase of the number of cycles, and the higher the temperature, the smaller the effect of the number of cycles. Under the action of temperature and stress, the dislocation starts to move from the disordered bending shape in the original sample to the flat shape gradually. Moreover, the dislocation density decreases to less than 47.8% of the initial sample as the temperature increases and the initial stress decreases. It can be concluded that the dislocation motion is the core mechanism of stress relaxation of Q235 steel.

To adapt to the intelligent management of traffic flow in modern aviation, this study improves the algorithm according to the data exercise method and establishes the mathematical model and vector model of intelligent motion coordinates. Moreover, according to the simulation test method, this study analyzes the six-degree-of-freedom equation of motion in the coordinate system of the civil aviation aircraft and uses the simulation method to regard the civil aviation as a rigid body with a certain mass and mass distribution. In addition, this study builds an intelligent model based on the demand analysis, and according to the actual demand, this study combines the simulation method to analyze the structure of the intelligent management model of air traffic flow. Finally, this study uses the experimental analysis method to verify the effect of the model proposed in this study and combines the experimental research to verify that the model proposed in this study has a certain effect.

In order to promote the application and development of civil aviation safety (CAS) in the field of safety and enrich the theoretical system of CAS research, the methodology of CAS was studied. The definition of CAS was reconstructed, its connotation was explained from four aspects, and its research object was clarified. This paper discussed the mechanism of CAS, that is, to maintain system security through the establishment of safety prevention and control system (SPCS), and explained the research content of CAS from theory and technology application. Five principles and applicable methods for CAS research were summarized. In addition, it put forward the general procedure of CAS research, explained the specific content and implementation method or basis of each step. The research results show that the methodology of CAS is a systematic theoretical system with certain guiding significance, combined with the mechanism, research content, research principles and methods, and research procedures of CAS. [ABSTRACT FROM AUTHOR]

A few years ago, a kind of dielectric scanning imaging logging instrument emerged in the foreign markets. That instrument scanned the earth at different frequency electromagnetic wave. It can measure the dielectric constant at different frequencies of the layer. There is not any similar instrument developed at home. Xi'an Shiyou University has launched a project to develop a comparable instrument. This paper introduces the basic principle of dielectric dispersion logging. A general layout is given for the dielectric dispersion logging. The time delay module is simulated and synthesized based on FPGA. This laid the foundation for the development of comparable instruments gradually. [ABSTRACT FROM AUTHOR]

Free-space optical communication receiver aperture is usually a single circular aperture. When the aperture size is large, its cost will be high. This paper proposes a new receiver aperture structure: equidistant dual-aperture receiver. The authors analyze its performance. Aperture Averaging Weight Factors of the two kinds of receiver structures are compared. The analysis results show that: Equidistant dual-aperture receiver can obviously decrease the Aperture Averaging Weight Factor, and reduce the optical scintillation. [ABSTRACT FROM AUTHOR]

Aiming at the operation processes of air traffic control, which analyses unsafe segments existing in the operation of ATC (air traffic control) from more than 60 civil aviation accidents and errors related to controllers, and expresses these unsafe segments from ATC in the form of the event tree, according to the accident case library evaluates severity of various events, and sums up the ATC factors that impact the unsafe segments; then transforms these human factors into Bayesian networks and counts the probability value of human factors through the field survey and statistics, which uses probabilistic safety assessment methods to determine the likelihood of various events; finally, assessment software simple and quickly applied in ATC operation, verified by practical applications, this method improves the efficiency and accuracy of safety assessment, can reach the targeted prevention ATC error, so as to make the right decisions for the operational risk control. [ABSTRACT FROM AUTHOR]

Free-space optical communication is a focus in recent research. Because of the influence of weather conditions, the transmission channel of free-space optical communication dramatically changes. This paper describes the design of a new adaptive rate-controlled optical communication system. The rate adaptively changes through the estimation of the received signal strength. Usually estimate the channel conditions with a low rate of radio frequency feedback. Previously the author used a new technique to design an adaptive rate-controlled optical communication system. It used beacon calibration instead of radio frequency feedback. In this paper an outdoor experiment is performed along a 186 meters horizontal path. On-off Keying modulation is used. The preliminary results with adaptive rate control are compared with that of without adaptive rate control. It appears to be at least an order of magnitude decrease of the bit-error rate. [ABSTRACT FROM AUTHOR]

In this paper, a new kind of method is developed to analyse the bit-error rate for a free-space optical communication system, which is based on the three most important parameters of scintillation statistics, i.e. fraction of time of fade and surge, mean frequency of level crossings, and mean duration of fade and surge. By using this method, the relationship between the bit-error rate and scintillation is clearly identified. The tip-tilt error deteriorates the performance of a free-space optical communication system. Fine tracking ability of adaptive optics (through tip-tilt compensation) can overcome this difficulty. The fade and surge statistical parameters with tip-tilt compensation are evaluated for the plane wave model. The bit-error rate as a function of the scintillation statistical parameters (with tip-tilt compensation) is developed. The results show that the bit-error rate is reduced notably through tip-tilt compensation for free-space optical communication. [ABSTRACT FROM AUTHOR]

Trend technology's theoretical model for atmospheric optical scintillation is establishes in this paper. For many years, people have always thought that atmospheric optics is completely random. In the previous paper, the author has used several experiments to over- turn the traditional view. In this paper, the author will put forward a model to explain the author's point of view theoretically. It will demonstrate the process how does the optical scintillation evolve according to the trend. In this paper, the author will give the second batch of the experimental data to verify the theory model. [ABSTRACT FROM AUTHOR]

Femtosecond frequency comb is a great invention in the field of metrology at the end of the last century. It can simply and effectively synchronize the phases for optical signals of different wavelengths or RF signals. Erbium doped fiber optical comb has many advantages. The National Time Service Center of Chinese Academy of Sciences has launched a project on the new type erbium-doped fiber femtosecond optical comb research. This paper introduces the signal source which is designed for this project. DDS chip AD9854 is used as the signal source. The signal source output has a wideband from 1-80 MHz. Test result for the signal source is discussed. [ABSTRACT FROM AUTHOR]

Horizontal docking assembly is a fundamental process in the aerospace assembly, where intelligent measurement and adjustable support systems are urgently needed to achieve higher automation and precision. Thus, a laser scanning approach is employed to obtain the point cloud from a laser scanning sensor. And a method of section profile fitting is put forward to solve the pose parameters from the data cloud acquired by the laser scanning sensor. Firstly, the data is segmented into planar profiles by a series of parallel planes, and ellipse fitting is employed to estimate each center of the section profiles. Secondly, the pose of the part can be obtained through a spatial straight line fitting with these profile centers. However, there may be some interference features on the surface of the parts in the practical assembly process, which will cause negative effects to the measurement. Aiming at the interferences, a robust method improved from M-estimation and RANSAC is proposed to enhance the measurement robustness. The proportion of the inner points in a whole profile point set is set as a judgment criterion to validate each planar profile. Finally, a prototype is fabricated, a series of experiments have been conducted to verify the proposed method.