Automatic interval management for aircraft based on dynamic fuzzy speed control considering uncertainty

A novel real-time autonomous Interval Management System(IMS) is proposed to automate interval management, which considers the effect of wind uncertainty using the Dynamic Fuzzy Velocity Decision(DFVD) algorithm. The membership function can be generated dynamically based on the True Air Speed(TAS) limitation changes in real time and the interval criterion of the adjacent aircraft, and combined with human cognition to formulate fuzzy rules for speed adjusting decision-making. Three groups of exper...     

A deep learning approach for velocity field prediction in a scramjet isolator from Schlieren images

Accurate measurements of physical parameters in a scramjet isolator are very important to promote the design and optimization of the isolator and even the scramjet. In a ground experiment, limited by the inherent characteristics of measurement technology and equipment, it is a big challenge to obtain the velocity field inside an isolator. In this study, a deep learning approach was introduced to combine data obtained from ground experiments and numerical simulations, and a velocity field predict...     

Concurrent multi-task pre-processing method for LEO mega-constellation based on dynamic spatio-temporal grids

The Low Earth Orbit(LEO) remote sensing satellite mega-constellation has the characteristics of large quantity and various types which make it have unique superiority in the realization of concurrent multiple tasks. However, the complexity of resource allocation is increased because of the large number of tasks and satellites. Therefore, the primary problem of implementing concurrent multiple tasks via LEO mega-constellation is to pre-process tasks and observation re-sources.To address the chall...     

Measurement method and results of divergence angle of laser-controlled solid propellants used in space propulsion

The plume divergence angle is an important reference index for evaluating the thrust efficiency and propellant utilization of space propulsion systems. However, the characteristics of the dynamic variation of plume divergence angle over time cannot be measured using current methods.This paper utilizes high-speed photography and image processing methods to develop a strategy that can give a quick, non-destructive and real-time detection of the divergence angle. Effectiveness of the strategy is ve...     

Research on Residual Stress Measurement of Magnesium Alloy Cabin Castings

Owing to the nonuniform wall thickness and complex internal structure, the measurement of the residual stress on magnesium alloy cabin castings is complex and difficult extremely, and thus seldom research has focused on the residual stress of magnesium alloy castings. In this paper, the blind-hole method, the X-ray diffraction (XRD) method, and the contour method are used to conduct comprehensive and systematic residual stress tests for a magnesium alloy cabin casting. The results show that the residual stress on the surface of the casting obtained by the blind-hole method is between -20.03 MPa and -71.03 MPa, the residual stress obtained by the XRD method is between -26.01 MPa and -87.11 MPa, while the residual stress obtained by the contour method is between -45.89 MPa and 76.87 MPa. The study can lay a basis for the subsequent research of magnesium alloy cabin castings, and provide a reference for the residual stress test of magnesium alloy castings.     

Kinematic calibration method with high measurement efficiency and robust identification for hybrid machine tools

Geometric error is the main factor affecting the machining accuracy of hybrid machine tools. Kinematic calibration is an effective way to improve the geometric accuracy of hybrid machine tools. The necessity to measure both position and orientation at each pose, as well as the instability of identification in case of incomplete measurements, severely affects the application of traditional calibration methods. In this study, a kinematic calibration method with high measurement efficiency and robu...     

Density-based ship detection in SAR images:Extension to a self-similarity perspective

Nonlocal self-similarity is an important property of Synthetic Aperture Radar(SAR)images to characterize the repetitiveness of features embodied by SAR images within nonlocal areas and has been used for enhancement of SAR images. Existing SAR ship detectors often independently handle small sub-images cropped from a large marine SAR image and do not exploit the nonlocal self-similarity therein. In this paper, we propose a new ship detector from the perspective of nonlocal self-similarity in SAR i...     

A Novel Approach for the Effective Thermal Conductivity of Porous Ceramics

A new approach in combination of the effective medium theory with the equivalent unit in numerical simulation was developed to study the effective thermal conductivity of porous ceramics. The finite element method was used to simulate the heat transfer process which enables to acquire accurate results through highly complicated modeling and intensive computation. An alternative approach to mesh the material into small cells was also presented. The effective medium theory accounts for the effective thermal conductivity of cells while the equivalent unit is subsequently applied in numerical simulation to analyze the effective thermal conductivity of the porous ceramics. A new expression for the effective thermal conductivity, allowing for some structure factors such as volume fraction of pores and thermal conductivity, was put forward, and the results of its application was proved to be close to those of the mathematical simula-tion.     

Probe design for measuring total temperature of combustor outlet based on water cooling

To obtain the outlet temperature of combustor, a kind of high-temperature and water cooling thermocouple was designed. The main factors affecting the results of thermocouple measurement were analyzed after numerical simulation. Results showed that the high-temperature water cooling thermocouple can achieve high temperature measurement under the condition of 2400K. With the increase of the distance between the water cooling structure and the stagnation cover, the temperature measurement result was more accurate, and the increase in the area ratio of the inlet and outlet of the stagnation cover within a reasonable range can make the measurement results more accurate. The surface emissivity of the measuring point had a great influence on the radiation error. The pressure and flow rate of cooling water can be effectively reduced after adding zirconia coating onto the surface of the rake body.      

Deformation Behavior of Medium-strength TA18 High-pressure Tubes During NC Bending with Different Bending Radii

To improve the forming quality and forming limit of the numerical control (NC) bending of high-pressure titanium alloy tubes, in this study, using three-dimensional (3D) finite element method, deformation behavior of medium-strength TA18 high-pressure tubes during NC bending with different bending radii is investigated. The results show that the cross-sectional deformation and the wall thickness variation during NC bending of TA18 tubes using a small bending radius (less than 2 times of tube outside diameter) are clearly different from that using a normal bending radius (between 2 and 4 times of tube outside diameter). For bending with a normal bending radius, with or without a mandrel, the distribution of the flattening in the bending area resembles a platform and an asymmetric parabola, respectively. For bending with a small bending radius, with or without a mandrel, the flattening both distributes like a parabola, but the former has a stable peak which deflects toward the initial bending section, and the latter has a more pronounced peak with a bending angle and deflects slightly toward the bending section. The wall thickness variations with a normal bending radius, with and without a mandrel, both resemble a platform when the bending angle exceeds a certain angle. For the bending with a small radius, the distribution of the wall thickness variation without a mandrel follows an approximate parabola which increases in value as the bending angle increases. If a mandrel is used, the thickening ratio increases from the initial bending section to the bending section.