Mega-Constellations Based TT&C Resource Sharing: Keep Reliable Aeronautical Communication in an Emergency

With the development of the transportation industry, the effective guidance of aircraft in an emergency to prevent catastrophic accidents remains one of the top safety concerns. Undoubtedly, operational status data of the aircraft play an important role in the judgment and command of the Operational Control Center(OCC). However, how to transmit various operational status data from abnormal aircraft back to the OCC in an emergency is still an open problem. In this paper, we propose a novel Telemetry, Tracking,and Command(TT&C) architecture named Collaborative TT&C(CoTT&C) based on mega-constellation to solve such a problem. CoTT&C allows each satellite to help the abnormal aircraft by sharing TT&C resources when needed, realizing real-time and reliable aeronautical communication in an emergency. Specifically, we design a dynamic resource sharing mechanism for CoTT&C and model the mechanism as a single-leader-multi-follower Stackelberg game. Further, we give an unique Nash Equilibrium(NE) of the game as a closed form. Simulation results demonstrate that the proposed resource sharing mechanism is effective, incentive compatible, fair, and reciprocal. We hope that our findings can shed some light for future research on aeronautical communications in an emergency.

Maximizing the probability an aerial anti-submarine torpedo detects its target

As a result of the high speed of anti-submarine patrol aircraft as well as their wide range, high efficiency and other characteristics, aerial torpedoes released by anti-submarine patrol aircraft have become the key anti submarine tool. In order to improve operational efficiency, a deep study was made of the target detection probabilities for aerial torpedoes released by anti-submarine patrol aircraft. The operational modes of aerial torpedoes were analyzed and mathematical-simulation models were then established. The detection probabilities of three attacking modes were then calculated. Measures were developed for improving low probabilities of detection when attacking a probable target position. This study provides an important frame of reference for the operation of aerial torpedo released by anti-submarine patrol aircraft.

Topological Optimization Method for Aeronautical Thin-Walled Component Fixture Locating Layout

Fixture locating layout has a direct and influential impact on aeronautical thin-walled component(ATWC)manufacturing quality.The purpose is to develop a topological optimization method for ATWC fixture locating layout to minimize the manufacturing deformation.Firstly,a topological optimization model that takes the stiffness of ATWC as the objective function and the volume of the locating structure as the constraint is established.Secondly,ATWC and the locating structure are regarded as an integrated entity,and the variable-density method based topological optimization approach is adopted for the optimization of the locating structure using ABAQUS topology optimization module(ATOM).Thirdly,through a subsequent model reconstruction referring to the obtained topological structure,the optimal fixture locating layout is achieved.Finally,a case study is conducted to verify the proposed method and the comparison results with firefly algorithm(FA)coupled with finite element analysis(FEA)indicate that the number and positions of the locators for ATWC can be optimized simultaneously and successfully by the proposed topological optimization model.

A Novel Onboard-gateway-based Mechanism to Improve TCP Performance in Aeronautical Satellite Networks

The IP-based networks on aircraft serve to support Intemet services via satellites. However, in aeronautical satellite hybrid networks, the TCP protocol performance often deteriorates due to improper decreases and slow recovery of the congestion window. This paper proposes a window size determination and notification mechanism, onboard-gateway-based mechanism （OGBM）, which is based on the onboard gateway in the networks on aircraft. A cross-layer approach is adopted by the onboard gateway to obtain the satellite link bandwidth information. And then, by the gateway, through changing the receiver＇s advertised window field in ACK packets, TCP sources are notified of the window size of each TCP source calculated on the ground of bandwidth delay product and flow numbers. The mechanism is able to avoid improper changes of TCP window and serve multiple users. Simulation results show that the mechanism with the fairness index close to l improves TCP performance in aeronautical satellite networks.

Relay movement control for maintaining connectivity in aeronautical ad hoc networks

As a new sort of mobile ad hoc network(MANET), aeronautical ad hoc network(AANET) has fleet-moving airborne nodes(ANs) and suffers from frequent network partitioning due to the rapid-changing topology. In this work, the additional relay nodes(RNs) is employed to repair the network and maintain connectivity in AANET. As ANs move, RNs need to move as well in order to re-establish the topology as quickly as possible. The network model and problem definition are firstly given, and then an online approach for RNs' movement control is presented to make ANs achieve certain connectivity requirement during run time. By defining the minimum cost feasible moving matrix(MCFM), a fast algorithm is proposed for RNs' movement control problem. Simulations demonstrate that the proposed algorithm outperforms other control approaches in the highly-dynamic environment and is of great potential to be applied in AANET.

Analysis and design of over-current limit control strategies applied in aeronautical power supplies

Some Over-Current Limit Control strategies are analyzed and designed to meet the demands of high reliability and rapid dynamic response in the aeronautical power supply applications. The control schemes are both effective in DC-DC converters and DC-AC converters. Controller models are set up, and the over-current limit operation principles of analogy and digital control are analyzed too. An 800VA aeronautical power supply bas been constructed to verify the performance of the proposed control strategy in various cases such as the sudden load change and the constant load. The analysis and experiments confirm the advantages of the proposed over-current limit strategies as follows： simple,effective and reliable.

ICI Cancellation Algorithm for OFDM Based Aeronautical Communication Systems and Its Performance Analysis

The aeronautical en-route communication channel is modeled as a two-ray double-selective channel. Based on the channel model, a low-eomplexity iteration self-cancellation algorithm is proposed to cancel the inter-carrier interference （ICI） of orthogonal frequency division multiplexing （OFDM） system in aeronautical communications. ICI can be completely suppressed by the proposed algorithm if channel parameters are estimated ideally. We analyzed the SNR loss with variant iteration times theoretically, and pointed out how to choose the optimum iteration times. The algorithm is especially useful to the situation with high aviation veloc- ity, as less iteration is sufficient to separate the interference with larger Doppler shift, and less noise will he introduced. We carried out Monte Carlo simulation with typical aeronautical en-route channel, and the simulation results are in agreement with the deduced theoretical performance expressions and validate the effect of our cancellation algorithm.

Route Optimization for Network Mobility Based Aeronautical Network Using Correspondent Router

The future aeronautical network will be based on IPv6 and the services over the aeronautical network will be classified into 3 domains: Air Traffic Services (ATS), Airline Operational Services (AOS) and Passenger Information and Entertainment Services (PIES), among which the ATS and AOS domains are important for aircraft safety and airline business operation. Some schemes have been proposed to provide IP mobility support for aeronautical network, and Network Mobility (NEMO) scheme is the most promising one. However, using NEMO technology will lead to sub-optimal routing, so route optimization technology is highly desired for NEMO. A route optimization scheme is proposed for the ATS and AOS domains, which introduces the Correspondent Routers to realize the optimal routing and employs an improved procedure to reduce the handoff delay. The route optimization for the PIES domain is also discussed to provide better performance for some special scenarios.

ANALYSIS ON CHARACTERISTICS OF AERONAUTICAL WIRELESS CHANNELS

In aeronautical mobile communication systems,wireless channels characteristics are dif-ferent in scenarios of Parking,En-Route,Taxi,and Arrival/Take-off.By considering fading types,power spectrum density and delay characterization of aeronautical wireless channels,typical parame-ters of aeronautical wireless channels model are investigated to analyze characteristics of aeronautical wireless channels.

AEROELASTIC TAILORING OF AERONAUTICAL COMPOSITE WING STRUCTURES

This paper deals with the aeroelastic tailoring of aeronautical composite wing surfaces. The objective function is structural weight. Multi constraints, such as displacements, flutter speed and gauge requirements, are taken into consideration. Finite element method is used to the static analysis. Natural vibration modes are obtained by the spectral transformation Lanczos method. Subsonic doublet lattice method is used to obtain the unsteady aerodynamics.The critical flutter speed is generated by V-g method.The optimal problem is solved by the feasible direction method.The thickness of the composite wing skin is simulated by bicubic polynomials, whose coefficients combined with the cross-sectional areas or thicknesses of other finite elements are the design variables. The scale of the problem is reduced by variable linkage. Derivative analysis is performed analytically.Two composite wing boxes and a swept-back composite wing are optimized at the end of the paper.

Development Trend of NC Machining Accuracy Control Technology for Aeronautical Structural Parts

High-performance five-axis computer numerical control machine tools are widely used in the processing of Aeronautical Structural parts. With the increase of service life, the precision of CNC machine tools equipped by aeronautical manufacturing enterprises is declining day by day, while the new generation of aircraft structural parts are developing towards integration, large-scale, complexity, thin-walled and lightweight. It is very easy to produce dimension overshoot and surface quality defects due to unstable processing technology. The machining accuracy of aircraft structural parts is also affected by complex factors such as cutting load, cutting stability, tool error, workpiece deformation, fixture deformation, etc. Because of the complexity of structure and characteristics of Aeronautical Structural parts, the consistency and stability of cutting process are poor. It is easy to cause machining accuracy problems due to tool wear, breakage and cutting chatter. Relevant scholars have carried out a lot of basic research on NC machining accuracy control and achieved fruitful results, but the research on NC machining accuracy control of Aeronautical structural parts is still less. This paper elaborates from three aspects: error modeling method of NC machine tools, error compensation method, prediction and control of machining accuracy, and combines the characteristics of Aeronautical Structural parts, the development trend and demand of NC machining accuracy control technology are put forward.

Hydration status,body composition,and anxiety status in aeronautical military personnel from Spain:a crosss-ectional study

Background: An adequate hydration status is critical to ensure efficiency during mental and physical activities.Our goal was to assess the hydration status of a Spanish group of aeronautical military men and to determine the association of hydration status with body composition and anxiety.Methods: A total of 188 men were evaluated through a validated hydration questionnaire, anthropometric and biochemical parameters, and an anxiety questionnaire. Based on these methods, the criteria of hydration were established.Results: Of the total sample, 81% met the hydration criteria(urine color = well hydrated, water balance ≥0 ml, and total water intake/weight ≥35 ml/kg), and 19% did not meet the hydration criteria(urine color = not sufficiently hydrated or dehydrated, water balance <0 ml, and total water intake/weight <35 ml/kg). Subjects not meeting the hydration criteria had lower urine pH, negative water balance, and lower water intake. The latter also had higher anxiety status(score=4 vs. 3, P=0.026), weight [(84.7±10.5) kg vs.(80.5±10.2) kg], body mass index [(26.3±3.1) kg/m;vs.(25.2±2.8) kg/m;], body fat [(22.3±5.6)% vs.(18.3±6.5)%], urine specific gravity, and urine color. Using a logistic binary regression model, hydration status was related significantly with the percentage of body fat(P=0.004), but no relation was found with age, comorbidities, or medications. Furthermore, total water intake/weight was positively correlated with percentage of body water(r=0.357, P=0.000) and negatively with body fat(kg)(r=–0.427, P=0.000), percentage of body fat(r=–0.405, P=0.000), and waist/hip ratio(r=–0.223, P=0.002). Based on a linear regression model, total water intake/weight was related significantly with percentage of body fat(P=0.001) and percentage of body water content(P=0.035). No relation was found, however, with waist/hip ratio, age, comorbidities, or medications.Conclusions: These findings all suggest a relationship between hydration status and body composition but also set the bases for future studies that relate hydration status and anxiety status. These results can be used to improve the hydration status and body composition of military personnel.

SURGE FORECAST FOR AERONAUTICAL ENGINES WITH EXTENDED KALMAN ESTIMATION

Abstract In this paper,the theory of extended Kalman estimation is applied to state estimate ofcompression system, for which a nonlinear model is developed by Greitzer.A criterion ofdetermining whether surge will occur in a turbine engine is presented.The combination ofstate estimation and the criterion of determining surge forms a surge prediction algorithm,which is the theoretical basis of designing a surge indicator for the turbine engine.

Chengdu Aeronautical Instrument Corp.

At the beginning of the 1980s, when international aeronautical instruments entered the microelectronic stage, the major products of the Chengdu Aeronautical Instrument Corporation were still outdated sensors, indicators, signal generators, and similar mechanical aneroid instruments, which lag far behind the advanced international level. Now computers, dealing with

Analysis of Maintenance and Inspection Status of Aeronautical Machinery and Improvement Countermeasures

In the daily operation process of airlines,aviation machinery maintenance and inspection work play an important role.At present,the quality of life of the people in our country is constantly improving.In daily travel,we have not only used cars,trains and other means of transportation,but also started to choose airplanes as the first choice in a higher frequency.In recent years,with the improvement of living standards,more and more people choose to travel during holidays.Therefore,the traffic volume of aviation aircraft is increasing year by year,but it also increases the risk of aviation aircraft failure,so it is particularly important to do a good job in the maintenance and inspection of aviation machinery.In this paper,according to the current situation of aviation machinery maintenance and inspection,put forward targeted improvement measures to ensure the safety and stability of China's aviation aircraft operation.

Brief Introduction of Transactions of Nanjing University of Aeronautics & Astronautics

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Transactions of Nanjing University of Aeronautics & Astronautics Information for Contributors

Transactions of Nanjing University of Aeronautics&Astronautics (TNUAA) is a bimonthly journal facing international academic community. Emphasizing prompt and effective dissemination of key data and new scientific insights, TNUAA offers publication of new experimental and theoretical papers bearing on applications to all branches of aeronautics, astronautics and civil aviation.