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About this book

This book presents high-quality contributions in the subject area of Aerospace System Science and Engineering, including topics such as: Trans-space vehicle systems design and integration, Air vehicle systems, Space vehicle systems, Near-space vehicle systems, Opto-electronic system, Aerospace robotics and unmanned system, Aerospace robotics and unmanned system, Communication, navigation, and surveillance, Dynamics and control, Intelligent sensing and information fusion, Aerodynamics and aircraft design, Aerospace propulsion, Avionics system, Air traffic management, Earth observation, Deep space exploration, and Bionic micro-aircraft/spacecraft.

The book collects selected papers presented at the 4th International Conference on Aerospace System Science and Engineering (ICASSE 2020), organized by Shanghai Jiao Tong University, China, held on 14–16 July 2020 as virtual event due to COVID-19. It provides a forum for experts in aeronautics and astronautics to share new ideas and findings. ICASSE conferences have been organized annually since 2017 and hosted in Shanghai, Moscow, and Toronto in turn, where the three regional editors of the journal Aerospace Systems are located.

Table of Contents


Test Research and Finite Element Analysis on Extension Performance of Civil Aircraft Flaps Subjected to Extreme Temperature

Aircraft climate test was conducted to investigate the effect of extreme temperature on extension performance of civil aircraft flaps in aircraft climate laboratory. Test results show extending the flaps to 10° requires 9.5 s, 7.8 s, 7.6 s when the standard equipped aircraft was kept at −40 ℃, 20 ℃ and 40 ℃ for the stipulated time, respectively. The lower the temperature is, the more difficult it is to extend the flaps. Furthermore, a finite element analysis (FEA) mode of the flap motion mechanism was proposed to reveal the influence of extreme temperature on deformation and drive torque of the flaps. Actual motion law of flap motion mechanism was adopted to describe behavior of flap motion mechanism under extreme temperature. The numerical research shows the drive torque decreases from −0.51 × 104 to −4.52 × 104 N mm when temperature rises from 20 to 74 ℃; conversely the drive torque increases from −0.51 × 104 to 27.5 × 104 N mm when temperature drops from 2 to −55 ℃. In addition, the lower the temperature is, the more obvious the deformation mismatch of the flap mechanism is, which may cause the friction to increase. The increasing friction due to the temperature drop results in the higher drive torque required to extend the flaps, which is also the reason that the time for extending the flaps to 10° increases with the decrease of temperature. The numerical results are observed to mutually agree with the test results mentioned above that the low temperature makes it difficult to extend the flaps.

Jingtao Wu, Sibo Zhou, Wenliang Deng, Yunwen Feng

Mathematical Modeling of an Environment Control System in the Framework of Creating a Comprehensive Mathematical Model of Aircraft On-Board Systems

The development and creation of modern aircraft is a complex technical process consisting of many iterations. Successful design and further operation of the developed aircraft models can be achieved only if there is the required amount of research at the design stage and when carrying out the full volume of tests. Also, when developing aviation technology, it is necessary to apply an integrated approach, for example, it is necessary to consider aircraft systems as a complex of interconnected systems, and not as separate, unrelated components. When developing technically complex aircraft systems, it is advisable to use mathematical modeling methods. The main aircraft systems of interest from the point of view of mathematical modeling (determination of the mutual influence of systems, maximum energy loads, optimization of aggregate parameters, etc.) and the formation of a complex of interrelated mathematical models are the following systems: power supply system (PSS), hydraulic system (HS); environment control system (ECS) and fuel system (FS). The study of the joint operation of these systems will allow not only an assessment of the parameters of the units and components of the systems, but also an assessment of the operation of the systems as a whole at various operating modes of the aircraft; working out the basic algorithms for controlling systems under various airplane operating modes, to determine the effect of failures of one system on the operation of other systems. In this paper, we consider in more detail the mathematical model of ECS. The main simulated characteristics in the mathematical model of ECS are: change in pressure and temperature in the system through pipelines and on key units (heat exchangers, turbomachine, shutters, etc.); changing the bleed air flow rate in bleed system in case of various operation mods, as well as at different values of the supported pressure in the cabin; change in air flow in the branches of the pipelines of the system with a mixture of hot air in accordance with the algorithms of operation of the valves, etc. A mathematical model of the key node of ECS—an air-cooling unit—is considered, simulation results for various operating modes are shown (airplane parking on the ground on a hot day, flying near the ground and flying at altitude). The developed mathematical model of ECS allows to use it both for evaluating the operation of nodes and units of the ECS, and for use as part of a set of interconnected mathematical models of the aircraft.

R. S. Savelev, K. S. Napreenko, A. V. Lamtyugina

Investigation on the Effects of Atwood Number on the Combustion Performance of Hydrogen-Oxygen Supersonic Mixing Layer

Combustion enhancement strategies are needed to improve the combustion efficiency of the supersonic shear layer. A 2D hydrogen-air supersonic shear layer with central jet filled of hydrogen and inert gas mixture under different Atwood (At) numbers is simulated, based on Navier-Stokes equations. The main purpose is to study whether optimal combustion enhancement can be obtained by changing fluid properties (At number). The Euler method cannot effectively identify the hidden flow field structure. Thus, the Lagrangian coherent structure method (LCS) is adopted to visualize the evolution process of vortex. Different Atwood numbers are adjusted by different inert gas ( $$\mathrm {N}_{2}$$ N 2 , $$\mathrm {Ar}$$ Ar , and $$\mathrm {He}$$ He , corresponding to At = 0.14, 0.26, 0.57) with identical mass flow of hydrogen. The obtained results show that combustion efficiency of the reacting cases tends to increase and then decrease, as At number increases. At = 0.26 has the best combustion efficiency which is mainly measured by the normalized mass production of water. Combustion efficiency of At = 0.26 is higher than that of other two cases because of the shorter vortex shedding distance and resulting larger burning area. Combustion performance is controlled by the mixing process. Vortex shedding position is found to play an important role in entrainment process which directly decides the combustion efficiency. The entrained oxygen can be completely consumed because of the excess hydrogen. In conclusion, shortening vortex shedding position helps improve mixing and combustion efficiency, which can be achieved by adjusting Atwood Number.

Chengcheng Liu, Zi’ang Wang, Bin Yu, Bin Zhang, Hong Liu

Analysis of Supersonic Axisymmetric Air Intake in Off-Design Mode

The most important issue in the design of a perspective aircraft is the development of a highly efficient power plant. One of the factors affecting its efficiency is the choice of air intake. The interest in this task is due to the fact that the operation of the air intake control program in various flight modes has a huge impact on the performance of the air intake device and, as a result, the power plant as a whole. The choice of the regulatory program is one of the most important types of work at the stage of forming the initial data when designing the power plants of aircraft (Bakulev et al. in Theory, calculation and design of aircraft engines and power plants, MAI, Moscow, 2013). The use of numerical modeling to solve various gas-dynamic problems allows us to expand the research range, and therefore, significantly reduce the number of experiments when practicing an air intake device. One of these tasks is to determine the characteristics of an air intake device in a wide range of flight speeds of aircraft. In this paper, we consider a supersonic axisymmetric three-shock air intake device of an external type of compression, numerical simulation of which was carried out in an application package for various operating modes. Based on the results of numerical modeling of the air intake device, a comparison is made to verify the design model, a solution is obtained to determine the optimum point for minimum losses in the off-design operation mode of the air intake device by changing the position of the central body without changing its geometry.

Svetlana Koval

Parameter-Orientated Functional Modeling Method Based on Flight Process

The system function execution intimately couples with the flight process, which is regarded as a critical factor to evaluate the system design comprehensively and precisely. Intending to establish the flight process-oriented functional model, this paper proposed a functional modeling method centering on parameter relationships, establishing the functional architecture of the system in multiple scenarios from the perspective of the flight process. Foremost, the functions of aircraft systems are categorized according to the application, then the system functional blocks of each category are further decomposed, with functional parameters and performance parameters embedded respectively. Progressively, the function completion status is constrained through the functional parameter relationships considering the dimensions of control demand, input parameters, physical components, etc., as well as the logic gates setting forth configuration relevance, and the specific blocks regarding the flight scenario collectively., rendering a comprehensive system-level functional architecture. The paper modeled the concrete functional flows of typical avionics systems, and evaluated functional completion status in various scenarios via Enterprise Architect, verified the efficiency and correctness of the method. The method facilitates the combination of the function model with the flight process, which is capable of measuring the rationality of the functional mechanism from an overall perspective in the early development stage.

Yuqian Wu, Zoutao Xue, Gang Xiao, Ke Gong, Xiaoxu Dong, Yue Luo

Experimental Study on Ice Shear Strength Evolution

Prediction of ice shearing performance on aluminum substrate is significant to develop de-icing technology for engineering problems. Ice shearing stress, which involves both adhesion and cohesion, varies with progression of substrate-icing both in temporal and spatial. Thus, study on evolution of both during substrate icing helps comprehensive understanding regularity of shearing performance. In this research, an experiment is designed to measure both ice adhesive and cohesive strength. Afterward, the evolutionary law is discussed with both physical and thermal theories. Experiment results show that substrate icing could be divided into several stage in sequence as “freezing”, “cooling” and “equilibrium”. Both adhesive and cohesive strength increases obviously in the freezing and cooling stage, while finally converges in the equilibrium stage. Such evolution of ice adhesive and cohesive strength are contribute to gradual change of temperature during vertical growing of ice layer. Finally, A model is established to evaluate the adhesive and cohesive strength via given initial temperature, time and position.

Gong Chen, Weiling Kong, Fuxin Wang

Investigation of the Effect of Electron-Beam Processing on the Surface of Samples Obtained by Additive Technologies from Cobalt-Chromium and Stainless Steel Powders

Products made of cobalt-chromium and stainless steel made by additive manufacturing methods are widely used in many branches of modern industry (aviation, mechanical engineering, shipbuilding and instrumentation, energy, medicine, etc.). Surface treatment with high-current pulsed electron beams (HPEB) is a promising method for further expanding the scope of these alloys. The article presents studies of the structural and phase state of the surface layer of samples before and after treatment with high-current pulsed electron beams, as well as the results of roughness measurements before and after irradiation with high-current pulsed electron beams.

E. E. Dzhafarov, K. M. Erikov, O. A. Bytsenko, A. V. Ionov

The Use of Basalt Plastic for the Manufacture of Sound Insulation Panels of an Aircraft Engine

The paper presents some information about the problems of noise produced by the engines. Recently, the international standards of the ICAO standard for aircraft noise reduction are constantly being tightened. The solution to this problem, in recent years, is the use of resonant sound-absorbing honeycomb panels installed in the air intake channel and in the external circuit of the engine. Today, due to the discrepancy in noise level, Russian aircrafts cannot fly on international lines with a full load. The reason for this is the lack of sound-absorbing characteristics of carbon fiber, as well as carbon fiber is quite fragile and not shock-resistant material, which also affects the operation of aircraft engines. In order to increase the acoustic efficiency and increase the strength characteristics of the aircraft engine hood, a variant of a three-layer honeycomb panel using basalt fabric and basalt-plastic fiber is being developed.

E. D. Moskvicheva, V. I. Reznichenko

Contour Segmentation of Image Damage Detection Based on Fully Convolutional Neural Network

Damage detection is a critical task in monitoring and inspection for aircraft internal structures. In the actual situation, most were nondestructive evaluation, such as ultrasonic inspection, which scan the internal structure of the aircraft, to obtain the damage inside for the testing parts. However, there is still no accurate standard for damage assessment and quantification on the scanned images by ultrasonic, due to the low image resolution, or the complicated scan result. The traditional contour detection algorithms, such as Canny Edge Detection (CED), color threshold, are difficult to apply on the damage contour segmentation for such images. In view of the progress of deep learning methods, the current study proposes a damage detection method based on Fully Convolutional Network (FCN), for the contour segmentation on ultrasonic detection of damage images. The whole FCN network for contour segmentation with the Visual Geometry Group (VGG) based is trained end-to-end on a set of 2000 256 × 256 pixels damage-labeled scanned images of a certain alloy which can be made for fan blade, another 400 images are used to test the FCN method. The contour extracted by FCN are qualitatively similar to the ground truth, achieve over 92% average precision. The FCN performance is better than the traditional algorithm, and the training model can be used for transfer learning to adapt to the extraction of different damage types. The results of segmentation can be further used for quantitative analysis of damage area.

Xuesong Zhong, Xiuhua Chen

A Study on Aerodynamic Interference for Truss Braced Wing Configuration

Truss Braced Wing (TBW) is one of the most promising configurations for future single-aisle commercial aircraft. The additional strut and jury in TBW endow the structure with better stiffness and strength, which enables a wing with larger aspect-ratio, thinner thickness and smaller swept angle, and even equipped with laminar flow airfoil. Theoretically, TBW configuration has the advantage of higher lift-to-drag ratio. However, one of potential problems for TBW is that severe disturbance may exist at the junction of truss and wing, which will reduce the aerodynamic benefit of TBW. To deal with this issue, this paper investigates influence of truss geometry on aerodynamic characteristics by numerical simulations of CFD. The Reynolds-averaged Navier–Stokes (RANS) method with the S-A turbulence model is used to compute the aerodynamic force and observe flow phenomenon of TBW in flight speed of Mach 0.73. The simulation results show that the geometric parameters that have large impacts on the cross section shape around the junction tend to have greater influences on aerodynamic characteristics (The Cross Section in this paper represents the cross section of air flow tunnel between the wing and truss). To analyze the impact of cross section geometry at the junction on the interference drag, we introduce a specific term, namely ‘flow section compression ratio’ that is the decreased rate of the cross section area from the entrance to the throat. The analysis indicates that the transonic disturbance will be considerable weaken when the ‘flow section compression ratio’ around the junction is under 16%, and the drag due to transonic disturbance accounts for only about 25% of the total interference drag. In order to further decrease the interference drag at the junction, we also investigate influences of the cross section geometry and airfoil thickness at the junction on the profile drag. The results from this paper can be helpful for TBW configuration design.

Lizhen Liu, Xiongqing Yu

Research on the Mechanism of Resistance Generation in Disc Acceleration Based on Lagrangian Method

During flapping wing flight or fish swimming, a large-scale vortex structure is in general generated by each stroke motion of the wing or the trail, and contributes most of the lift and thrust. As a fundamental model to characterize the wake structures of flapping flight and fish swimming, the disc vortex ring (DVR) generated by the impulsive motion of a disc contains numerous unsteady aerodynamic mechanisms. In this paper, an experimental set-up was designed to produce DVRs with different acceleration, particle image velocimetry (PIV) technique was used to measure the growth and evolution process of wake vortices, and force sensor was used to measure the instantaneous change in drag directly. PIV results show that a DVR is formed in the wake during the disc starting, and the circulation growth of DVR satisfies the Logistic growth model. Using the Lagrangian coherent structure (LCS) to analyze the formation of DVR shows that, under the interaction of the add-mass effects of disc and DVR, the vortex flow shows a significant Lagrangian drift, which contributes a significant increase of the drag. Besides, the results of the drag measurement show that the formation process of the vortex ring consists of three phases, including a peak and a valley. Based on the vorticity-moment theorem, the evolution of drag is explained in terms of the dynamics of DVR and the added-mass effects. Moreover, the findings of this paper provide a new Lagrangian perspective for understanding the mechanism of lift and thrust during flapping wing flight and fish swimming.

Shujia Lin, Fuxin Wang, Zhuoqi Li, Yang Xiang

A Review of Supersonic Turbines Based on Constant Volume Combustion Cycle

In this paper, in response to the current demand for new aerospace power in the aerospace field, thermodynamic performance and thermal efficiency advantages of existing constant volume combustion cycles are reviewed. The main challenge in the practical implementation of Pressure Gain Combustion (PGC) into gas turbines and aero-engine is the lack of turbomachinery that can efficiently harvest work from the PGC exhaust gas. Therefore, this paper analyzes the supersonic inflow conditions with pressure, temperature and velocity pulsations at the outlet of the detonation combustion chamber, and puts forward the difficulties brought by the inflow conditions to the design of the turbine cascade. Secondly, this paper analyzes the aerodynamic characteristics of turbine cascade passage under supersonic inlet conditions, analyzes the influence of channel shock waves on aerodynamic losses, and expounds the importance of turbine under supersonic inlet conditions in detonation combustion cycle.

Liangjun Su, Fengbo Wen

An Application of QFD in Aircraft Conceptual Design

Aircraft conceptual design is the very beginning of aircraft design process in which one or several aircraft configurations are created to meet the top-level requirements of aircraft. The aim of this paper is to build a more traceable, structured and systematic process of aircraft conceptual design by use of Quality Function Deployment (QFD) method. The conceptual design of a narrow body commercial aircraft is used as an example to illustrate application of the QFD. The top-level requirements of the commercial aircraft are defined. The conceptual design activities such as initial sizing of aircraft, wing configuration design, fuselage configuration design, and empennage configuration design are accomplished using House of Quality (HOQ). During initial sizing of aircraft, the top-level requirements of aircraft are converted into the requirements for aerodynamics, propulsion and weight with the aid of HOQ and constraint analysis. During configuration designs of the wing, fuselage and empennage, their requirements are identified based on the top-level requirements and output of the initial sizing, and consist of requirements of aerodynamics, structure, control, safety, operation, cost and etc. Several HOQs representing the relationships between the requirements and the configuration design parameters are created. After that, the configuration design parameters are selected with the aid of the HOQ and relevant design knowledges. By use of the QFD, aircraft conceptual design activities are represented by a number of the HOQ and the design process of configuration parameters is traceable through the HOQ. It is concluded that the QFD-based aircraft conceptual design is more traceable, structured and systematic than the traditional method.

Shiyu Wang, Zhouwei Fan, Xiongqing Yu

Parametric Optimization of the PCM Caisson Structural Strength Elements

In modern passenger aircraft, polymeric composite materials (PCM) are used to ensure the mass excellence of both lightly loaded elements and aggregates, including wings and feathers caissons. The use of such materials instead of metal alloys makes it possible to reduce the weight of structures, increase the service life, and reduce the complexity of manufacturing and material consumption. Based on the finite element method, a caisson model was created using shell finite elements (FE), considering the anisotropic properties of PCM. To solve the problems of buckling of the elements of the caisson from the PCM, a method of analytical optimization of the stringers pitch and web plates has been developed. Analytical calculation of the local model based on the loads obtained from the global shell finite element model (FEM). The developed methodology allows obtaining a design of a caisson with a minimum mass while maintaining the necessary stiffness and strength characteristics.

Aleksandr Bolshikh, Valentin Eremin

Influence and Correction of Satellite Phase Center Offsets for RNSS Performance of BDS-3

BDS-3 provides three kinds of Radio Navigation Satellite Services (RNSS), including primary Positioning Navigation and Timing (PNT), Satellite Based Augmentation System (SBAS) and Precise Point Positioning (PPP). Satellite phase center offsets are important error sources for service performance. Misalignments of frequency-dependent phase centers decrease the service performance further. Therefore, approaches accounting for satellite phase center offsets and the misalignments are prerequisite for satisfactory service performance. Phase center offsets induced errors on ranging and positioning accuracy are analyzed. Different feasible approaches accounting for phase center offsets are presented with reached accuracy. Finally, optimal approaches accounting for the phase center offsets are concluded for all the kinds of RNSS services with real measurements.

Cheng Liu, Weiguang Gao, Chengpan Tang, Wei Wang

Effects of Tube Wall Thickness on Combustion and Growth Rate of Supersonic Reacting Mixing Layer

The study of supersonic reacting shear layer has been paid great attention to further understand flow characteristics and mechanism of the engine combustion process. However, most past studies remain narrow in focus dealing only with infinitely small tube thickness or fixed ones which neglects the complex flow structures reflecting some general features of scramjet engine mixing and combustion process. In the present study, supersonic reacting mixing layer has been studied under different tube thickness. Numerical simulations have been carried out with CFD++ 14.1 to solve the Reynolds averaged equation on the Evan’s configuration which is closed by Menter’s Shear Stress Transport turbulence model and finite reaction rate chemical kinetic model. The flow field evolution, mixing layer growth and combustion ignition are the major focus of current study. The obtained results show that the existence of finite tube thickness brings unique flow field characteristic such as expansion fans and shock systems which is not included in the tradition simplified analysis of reacting shear with infinitesimal tube thickness. The tube thickness has a positive effect on growth of mixing layer and ignition delay that 50% of decrease in ignition delay has achieved by enough tube wall thickness.

Di Lu, Fang Chen

An Investigation for Effective Thermal Properties of Titanium Alloy Lattice Sandwich Panels

Multifunctional sandwich panel presents a unique Integrated Thermal Protection System (ITPS) for hypersonic vehicles. In this paper, a novel method to evaluate the effective thermal properties of metal alloy lattice core sandwich panels is presented. The thermal transfer process between lattice core and face sheet was analyzed, and the behavior schemes were detached in three categories according to the existence of insulation material filling and active convection. For each category, equations were presented to calculate the effective density, specific heat and thermal conductivity for pyramid lattice core and tetrahedral lattice core using Representative Volume Element (RVE). Two sandwich panels were constructed separately with the two lattice cores made by the material of titanium alloy. Numerical Simulation based on Finite Element Method (FEM) was employed to verify the effective techniques. Two kinds of FEM models were built with detailed solid element level and simplified effective solid element level. The heat transfer process from top sheet to bottom sheet across lattice core were simulated, consistency of temperature responses could be observed obviously between the different level FEM simulations. It could be concluded that the effective properties deduced with the method in this paper are accurate to predict the thermal performance of titanium alloy lattice core sandwich panels, and are very promising for potential application in the analysis and design of TPS for hypersonic vehicles.

Junpeng Li, Zhibin Yang

Modeling and Analysis of Gate to Gate Flight Process Based on SysML in Commercial Aircraft

The design and development of commercial aircraft is a complex system engineering. At present, operational scenario analysis is gradually used for aircraft function identification and requirement capture. In the analysis process, the time dimension factors of the aircraft in civil aviation operations must be considered, that is, the complete process of aircraft operation must be defined. Guided by the idea of system modeling, this paper presents research on the modeling method of Gate to Gate flight process. The basic elements and hierarchical division of flight process models are constructed. Finally, the paper proposes the method and procedure of establishing Gate to Gate model based on SysML. Based on the previously proposed method and a complete description of commercial aircraft operation process, this paper establishes a summary behaviour model of aircraft's Gate to Gate flight process, covering the preparation before takeoff, push back, taxi out, taxi before takeoff, takeoff roll, takeoff, climb, ocean-based cruise, land-based cruise, descent, approach, final approach, landing, taxi after landing, and taxi to aircraft stand. SysML is used to model the flight process, which includes aircraft itself, ATC, AOC, airport tower and other models. The model is drawn to form Use Case diagrams, Activity diagrams, State Machine diagrams, and Sequence diagrams under each flight phase. The model mainly focuses on the collaborative process between aircraft and various stakeholders, such as the collaborative interaction process between aircraft and ATC, AOC, as well as the collaborative interaction process between aircraft and airport tower during the takeoff and landing phase. This paper provides a method to describe the flight process systematically and graphically. It can also be used as an exploration of function identification and requirements capture methods.

Hongyu Li, Miao Wang, Gang Xiao, Guoqing Wang, Bei Tian, Zihang Chen

Research of Commercial Aircraft's Battery Layout Design Method Based on Ditching Situation

From Airworthiness regulation, the electronic power supply system must meet the requirement of power demanding devices which are used to support emergency evacuation of passengers, during emergency landing, including ditching situation. In this situation, the main power supply is often failure, and battery will supply power instead. However, after ditching, the fuselage structure is often damaged, water will flow over into fuselage, if battery, charge or wires are under water and short circuit, then all the devices which are used to support emergency evacuation will failure to work, and passenger evacuation will be very dangerous. For this problem, this paper researches the ditching floating characteristics of commercial aircraft, especially the leakage time of compartment, time-variation of water level, etc. At the same time, this paper analyzes the time of passenger evacuation. Based on those impact facts, this paper researches the battery layout design method of commercial aircraft.

Li Wen Wu

Model-Based Surface Trajectory-Based Operations Analysis in Airport Surface Management

The efficiency and safety of airport surface operations have long been a hot topic in air traffic management domain. The current mode of surface operation management in civil airports is mostly based on the constraint point concept, which does ensure the safety of surface operations but, in quite a lot causes, leads to a waste of time and causes delay in civil airlines. The related researches focus mainly on the improvements of navigation accuracy and the development of surveillance technology, yet they would not escape from the inherent ceiling of the constraint point mode itself. The research of this paper is inspired by Surface Trajectory-Based Operations (STBO) concept. The STBO concept suggests that the new mode of air-port surface operation management will allow the strategic automation to develop routes that deliver aircraft to runways and taxiway intersections in a conflict-free manner with the help of 4D trajectory. In the research, the models of some typical surface scenarios are built according to the joint operations in between aircraft, airline and air traffic control with system modeling language, which meet the requirements of specifications and instructions of surface operations. The modeling is carried out in control experiments where one is under constraint points theory and the other is under STBO concept in the same surface scenario. The results are show that the latter one provides adequate safety and better efficiency than the former one in studied scenarios. It is just a start in the exploration of new mode in airport surface management, and the further implement and improvements of STBO concept is looking forward to lead the air traffic management to a new era.

Wenhao Zhao, Miao Wang, Gang Xiao, Guoqing Wang

Development and Application of a Functional Analysis Method for Aero Engine Requirement Management

Civil aero engine is a typical complex product, the development of complex product and system is characterized by high comprehensive integration, high functional coupling. With the development of technology, the design of civil aero engine has become more comprehensive and not only requires the high performance, high reliability, long-life, but also need effective approaches to create successful products. Systems engineering is a methodical, recommend approach for the development of complex product, and functional analysis plays an important role in systems engineering of requirement management process, by using a functional analysis method capture and analysis the function of civil aero engine improve the completeness of requirements, and provide a common understanding of the product. In this work, a functional analysis method is illustrated based on operating modes and using context diagram to identify functions of system. The proposed approach is studied and applied to propulsion system to prove that the method is effective. The typical operating modes of propulsion system are outlined, and the functions of propulsion system promote the definition of requirement document. Furthermore, the functional analysis method can also be widely used in aero engine systems and sub-systems and component levels.

Yan Ji, Zhenyu Sun, Zhimin Li

Research on Civil Aero Engine Requirements Development and Management

Aero engine not only need to meet aircraft requirements and also airworthiness and other stakeholder’s requirements. Due to the increasing complexity of requirements, the development of civil aero engine within the required time and cost present a considerable challenge. In this work, a requirements development and management approach is introduced in civil aero engine development process, the aim is to bring forward new experiences on aero engine requirements management in practice. The requirements and design definition is presented in a requirement V model and the aero engine design is decomposed from the whole system to sub-systems and then to the components, a typical civil aero engine requirements architecture is defined. Based on the requirement development model, the requirements related files of aero engine are illustrated. The requirements flow down case shows how requirements allocate and interacting between systems. By managing the status of requirements throughout the whole engine development, the traceability between requirements and design and verification data are established to ensure the consistency of requirements.

Zhenyu Sun, Yan Ji, Zhimin Li

Investigations on the Acoustic Resonance in Aeroengine Multi-Stage Compressor

Acoustic resonance, which is caused by the coupling and interaction of flow and acoustic field in aeroengine, can not only produce noise with very high amplitude in compressor, but can also lead to the fatigue of the materials and endanger the structural integrity of aeroengine. Unlike the unsteady flow phenomenon such as surge, rotating stall, and rotation instability, researchers still cannot fully explain and understand acoustic resonance well, because there are only few investigations about acoustic resonance and the coupling between acoustic and flow field is quite complicated in the aeroengine. Thus, this study firstly summarizes the phenomenon of acoustic resonance, and systematically describes its characteristics. After that, some theoretical models and methods used for the prediction of the acoustic resonance is introduced. Finally, proper orthogonal decomposition method is firstly proposed and applied for the study of acoustic resonance. A full passage unsteady numerical simulation is demonstrated with this method.

Zihao Wu, Xiaohua Liu

Computational Method in the Throughflow Simulation of Aeroengine Compressor

The computational method in throughflow simulation is investigated in this paper. The present investigation reported the current research status and compared the advantages and disadvantages between different computational models including streamline curvature method, matrix method and throughflow calculation based on time marching. For the most commonly used time marching method, we discussed one key issue in application in engineering reality which is called as the simulation of blade force, which was divided into two categories according to whether to solve the circumferentially momentum equation as master equation or not. In conclusion, compared with other methods, time marching method has more advantages in transonic flow adaptability, shock capture ability and calculating accuracy, so that it has more potentials and prospects in the future research. The blade force model, as a key link in the time marching method, has developed rapidly. However, there is still no unified highprecision model and the modeling of blade force needs more study. With further development, this method is expected to become a standard tool during the aeroengine compressor design stage.

Qitian Tao, Hailiang Jin, Xiaohua Liu

Rotating Beamforming in the Frequency Domain for an Incomplete Microphone Array

As society developed expeditiously, more attentions have been paid towards harm of noise. Thus beamforming technology based on phased microphone array is widely used in rotating acoustic source localization. In this paper, a ring microphone array is placed parallel to the scanning plane with the array located on the z-axis. However, the microphone and the rotating part are not allowed to be too close for the potential suction danger caused by the rotating part. At present, this problem has not been solved in engineering.This paper proposes a new method to measure the rotating parts safely by a ring microphone array with a large enough diameter. The diameter of the array is too large more than twice the distance from the array center to the ground. Hence, some microphones cannot be installed. In this paper, the symmetry of the ring array perpendicular to the ground is taken as the center. Moreover, an odd number reduces the number of microphones in turn. Then, the positions and levels of the maximum sound are compared with the previous case which does not reduce the microphones by observing the beamforming result.When reducing the total number of microphones by less than a quarter, the resolution of the beamforming result decreases gradually while the maximum sound strength increases, and the position of the maximum sound pressure moves slightly. The deviation of the maximum acoustic pressure position can be ignored, and the change of the maximum sound pressure level is very small.

Mengxuan Li, Wei Ma, Wei Zhou

Comprehensive BDS-3 Signal Simulating for Strong Ionospheric Scintillation Studies

The construction of BeiDou Global Navigation Satellite System (BDS-3) is near complete and ready to provide worldwide navigation services soon. As compared to other navigation systems, BDS-3 has superiority that it is the first navigation system fully broadcast triple band signals and utilizes more advanced modulation, i.e. Binary-Offset-Carrier (BOC) modulation to achieve the enhanced accuracy and anti-interference performances. BDS-3 will play an important role in various high precision navigation applications. However, strong ionosphere scintillation will pose a great threat to GNSS accuracy and robustness and BDS-3 has no exceptions. Strong ionospheric scintillations will cause severe signal fluctuations, i.e. simultaneous deep amplitude fading and fast phase fluctuations. It will deteriorate the range measurement accuracy, affect the PNT (positioning, navigation, and timing) performances, and even destroy receiver functioning in some extremely cases. Therefore, the investigation of ionospheric scintillation effects on GNSS signals, especially on novel BDS-3 signals are quite necessary. In this paper, a comprehensive study of a strong scintillation BDS simulator will be carried on the basis of an open source GPS scintillation simulator provided by the SenSe Lab in University of Colorado Boulder using the two-dimensional two-component power-law phase screen theory. The BOC modulation is implemented and integrated in the simulator, so that the raw data of six BDS scintillation signals on three frequency bands, i.e. B1I, B1C (data + pilot), B2a (data + pilot), and B3I are simulated for test. To validate the effectiveness of the signal simulator, the realistic BDS scintillation data was collected, analyzed, and compared with the simulator outputs. The comprehensive simulator presented in this paper will be a tool to facilitate the ionospheric studies as well as advanced GNSS receiver development in future.

Jihong Huang, Xingqun Zhan, Rong Yang

Fan Broadband Noise Localization and Mode Identification Technology in Turbofan Engine

Microphone array measurement technology is widely used for aeroacoustic measurement, because it has the advantages of being far away from strong mutual interference regions, which can avoid intrusion of the flow field, increasing the size can improve the spatial resolution and increasing the number of microphones can promote dynamic range. As the ducting ratio of civil aeroengine increases, the proportion of fan noise is increasing. In the fan noise, the development of tone noise reduction technology is more mature which makes the problem of broadband noise more prominent. However, the mechanism of broadband noise generation is complicated and signal-to-noise ratio is relatively poor, which make it difficult to control broadband noise. Efficient and accurate in-duct fan broadband sound source localization and mode identification can be realized by arranging a ring or multi-ring microphone array around the duct, which can greatly assist the fan broadband noise reduction technology. This paper summarizes the in-duct rotating broadband noise localization and mode identification technology developed in foreign countries in recent years, namely the in-duct rotating beamforming and the mode beamforming, which use the experimental data provided by the University of São Paulo in Brazil for code verification and compare the calculation results with conventional beamforming and mode decomposition. The results show that the in-duct rotating beamforming has higher source resolution and dynamic range. The mode beamforming with multi-ring array has better radial modal identification capability than the mode decomposition. Finally, the advantages and disadvantages of the new technology and the future improvement direction are expounded.

Jingnan Chen, Wei Ma

Performance Evaluation of Robust GPS Signal Tracking with Moving Horizon Estimation in Urban Environment

The rise of autonomous drive imposes new challenges in terms of robustness and precision of Global Navigation Satellite Systems (GNSS) technology, especially in the urban environment. The conventional GNSS signal processing usually takes Kalman filter (KF) as the signal parameter estimator to enhance the tracking performance, however, this is not a promising design for the urban navigation application where the signal blockages and severe multipath interferences are frequently occurred. To address this issue, a moving horizon estimator (MHE) will be used to replace KF for the accuracy and robustness improvement. Unlike the KF that highly depends on the accurate modelling of the system and measurement characteristics and cannot afford random outliers and distortions, MHE can incorporate the constraints, e.g., a priori defined variances, to limit threats from the faults, interferences or invalid measurements. Therefore, MHE is less sensitive to the random environmental variations as compared to EKF, which makes it more robust and more applicable to urban environment. The proposed tracking algorithm is verified with a realistic road test near Lujiazui CBD area in Shanghai in post-processing manner. The results confirm the improved accuracy, reliability, and robustness by using MHE method.

Jiawei Xu, Rong Yang, Xingqun Zhan

Feasibility Exploration on Simulation Study Based on Peridynamic for the Bio-Inspired Nacre Nano Composite Against the Impact

The deformation and failure of materials and structures under high speed impact is a major problem in aerospace, automotive engineering and protection engineering. In this paper, based on peridynamics (PD) model, the deformation and damage mechanism of the bio-inspired nacre nanocomposite against the impact was discussed. According to the existing experiments, the crack evolution and propagation process of “brick-mortar” split-layer microstructure under the impact were approached systematically. According to the result that impact damage only occurs on the top of bio-inspired nacre nanocomposite, it is concluded that peridynamics can be well applied to the analysis of nacre nanocomposites under impact.

Zhiwei Zhou, Shufan Wu, Zhongcheng Mu, Wei Wang, Ningjing Jiang

An Interface Management Approach for Civil Aircraft Design

The interfaces between on-board systems play a very important role for a civil aircraft, which primarily involve the signal, material and energy exchanged be-tween relevant systems in the aircraft. It is believed that a uniform interface management can remove and reduce conflicts between systems in the aircraft integration. It is necessary and essential to perform the interface management in an effective and uniform manner throughout the whole aircraft development life cycle to identify, validate, control, and verify the interfaces to ensure all the sys-tems integrated properly according to the given expectations. An interface management and development approach is proposed, which is composed of four phases, i.e. interface architecture definition, interface identification, documentation and change control. An interface development and management case is pro-vided, which demonstrates that the proposed approach can not only effectively assist system engineers in capturing various types of interfaces, but also can ex-press interfaces in an unambiguous way, which allows engineers to develop a shared understanding about interface requirements. It is also found that the inter-face management approach can control the interfaces in the whole aircraft development life cycle, which is beneficial to aircraft integration.

Dake Guo, Xinai Zhang, Jiejing Zhang, Haomin Li

Finite Elements Modeling of Randomly Oriented Short Fiber-Reinforced Composite Materials

Randomly oriented short fiber-reinforced composite materials are getting more and more popular due to its manufacturing simplicity and low cost compared with conventional continuous fiber-reinforced composites. Because of the randomization in fiber orientations, it is relatively difficult to simplify and establish its material model for analytically predicting material properties. Therefore, it is important to have a numerical approach to generate computational models and perform analyses. Finite Element (FE) modeling is the most widely and commercially applied modeling technique. It is now a vital and irreplaceable tool in many industries such as automotive, aerospace, defense, consumer products, architecture and many others. This present work demonstrates a FE modeling approach of a Representative Volume Element (RVE) for short fiber-reinforced material. The RVE consists heterogeneous micro-structures for fiber and matrix individually, it is meshed with first-order tetrahedral element. Periodic boundary conditions are applied on the lateral surfaces of RVE in the numerical implementation so that the effective material properties can be obtained.

Daniil Lupachev, Yile Hu

Capturing and Defining Interface Requirements in Commercial Aircraft Development Program

With the increasing customer expectations s and the development of civil aircraft design technology, the functions to be performed by the civil aircraft systems become more and more complex. Meanwhile, those functions will interact deeply with complex logical and physical manners to complete different missions indifferent operation scenarios. Used to describe the information, data, geometry constrains and logic between two interacting functions, interface requirements play an extremely important role in not only the aircraft architecture development process, but also the aircraft integration and verification process. Therefore, it is essential to capture and manage all the interfaces completely and properly to ensure the aircraft as well as the onboard systems to perform the expected functions under some certain operation scenarios. All onboard systems development terms will define their required and provided interface information according to the system architectures and characteristics concurrently. It is required to define an interface development process in order to take on the above challenge, which often results from ambiguous expression of interface requirements, and the difficulty in managing huge amount of data about interface requirements, and in the control frequent changes. Based on the generic aircraft development process, this paper proposes a systematic approach for capturing and defining interface requirements. The interface development and definition activities throughout the aircraft program life cycle are elaborated in details. The interface classifications and the corresponding interface types and examples are introduced. The interface topology relationship and data model is investigated and defined, which forms the basis for the interface linkage and interface management database development. A case study is carried out to demonstrate the interface requirements development approach proposed here. It is found that the structural interface development process is helpful for engineers to capture the interface together with relevant attributes, which are represented in a uniform and unambiguous format and therefore can serve as the basis for relevant stakeholders to understand the interface definition. A significant advantage of the proposed approach is that it allows systems engineers to arrange the huge amounts interface together with interface attributes according to the interface classifications and types. It also shows that the interface data topology architecture enables engineers to establish traceabilities between interface requirements, which is beneficial to change impact analysis and interface consistent check.

Jiejing Zhang, Xinai Zhang, Haomin Li, Dake Guo, Yong Chen, Kaili Zhang

Features of the Use of Damper Supports of Various Designs in a Gas Turbine Engine

This article discusses the features of using various designs of elastic-damping devices on GTE supports, including: support with a hydrodynamic damper (with and without an elastic element), support with an elastic ring and support with a plate damper. An analysis of their design is given in terms of the impact on the stiffness and damping of the engine support unit, which allows you to determine the choice of a damping device for solving the complex problem of reducing engine vibrations.

N. S. Konoplev, L. V. Farsiian, A. V. Davidov, M. K. Leontiev

Research on Integration Technology of Stereoscopic Environment Monitoring System Based on UAV

In this paper, the researchers built a three-dimensional air pollution monitoring system based on a multi-rotor UAV platform, and did research on the system integration technology. (1) Anti-outflow Field interference measures. We used adjustable speed ducted fans to stabilize the airflow, and set the airway to further improve the intake stability and reduce the interference of the flow field around the drone to the measurement equipment. Optimizing the installation location of the equipment according to the CFD simulation results; (2) Anti-electromagnetic interference treatment. By wrapping the electromagnetic shielding cloth (silver fiber fabric) on the measurement module, the electromagnetic interference generated by the UAV’s own device on the sensor module is reduced; (3) Data preprocessing. Before the regional measurement, an airborne control test was carried out, and the data collected by the airborne equipment was corrected using data processing methods. The equipment was equipped with an Internet of Things module and a GPS positioning module, so that the measurement data could be transmitted to the background for analysis in real time. (4) Based on the uniform experimental design method, the UAV inspection points are arranged, and the measurement path of the measurement system is optimized. And carried out on-site measurements in Xi’an, China.

Weigang An, Liu Liu, Yanping Wang, Wei Zeng, Le Wang

Effects of Transition on Aerodynamic Characteristics of Laminar Airfoil Based on CFD

Laminar airfoil has extensive application prospect in the civil aviation area as its low drag characteristic. However, the laminar flow is too sensitive to be disturbed and then laminar-turbulent transition location will move forward, which results in a significant increase in drag. Therefore, it is meaningful to obtain the aerodynamic characteristics of laminar airfoil both under natural transition and disturbed transition conditions. This paper focuses on the aerodynamic characteristics of a laminar airfoil named NACA65(1)412. Firstly, numerical simulations of natural transition of the airfoil flow at various angles of attack were carried out using γ-Reθ model. Secondly, forced transition simulations were taken to imitate the disturbed airfoil flow using k-ω SST model. Results show that, the transition location has a great influence on the aerodynamic characteristics of laminar airfoil, especially on the drag. For the natural transition, as the angle of attack increasing, the natural transition location on the upper surface moves upstream while the one on the lower surface moves the opposite. The upper-surface transition location moves upstream rapidly after the 4° angle of attack. For the forced transition, the drag increases approximately linearly with the transition location for both the upper and lower surface, but the upper-surface behaves much more significant. The lift changes little with the movement of transition locations.

Yanping Zhao, Lianghua Xiao, Yao Chen, Rui Chen

4D Trajectory and Controller Command Generation Based on Schedule Time of Arrival

In order to support the construction of ATC automation system, a four-Dimensional Trajectory (4DT) and controller command generation method based on Schedule Time of Arrival (STA) is proposed. Firstly, four main models of trajectory generation are given: point-mass model, performance model, weather environment and intention model, and the process of trajectory generation is described. Secondly, two methods of generating 4DT according to STA are studied, which are adjusting speed parameters and adjusting command timing. Finally, Guangzhou Baiyun airport is simulated as an example. The result indicates that both optimization methods can meet the requirement of STA, but the command-based method is more consistent with the current control mode, which has a broad application prospect.

Jie Liu, Shuoyan Zhang, Jizhi Mao

The Mechanisms of Albatrosses’ Energy-Extraction During the Dynamic Soaring

Albatrosses are the soaring champion among the birds, they can travel 1000 km per day without eating or rest, scientist summarizes this flying style as dynamic soaring. This paper is focusing on the mechanisms of dynamic soaring, by derivation energy harvesting equation, link the basic variables which could infect gliding performance. Through analysis two different energy-extraction equation in two different reference system, this paper finds the key to dynamic soaring and provide a new concept of bionic unmanned aerial vehicle (UAV) design.

Wei Wang, Weigang An, Bifeng Song

Aerodynamic Design and Optimization of Bionic Wing Based on Wandering Albatross

The aerodynamic characteristics of the wing largely determine the flight performance of the aircraft. In studies of nature, it has been found that albatrosses can travel thousands of miles over the sea, with little flapping of their wings, because of their lift-and-drag properties. In order to further study the aerodynamic performance of albatross wings, this paper extracts the mathematical model of bionic wing according to the shape parameters of a wandering albatross, and selects GOE 174 airfoil as the airfoil of bionic wing by 2D aerodynamic analysis, and finally designs and establishes the three-dimensional model of bionic wing. Considering the individual size differences of wandering albatross and the wing deformation during dynamic flying, the Genetic Algorithm(GA) and Vortex Lattice Method(VLM) were used to optimize the size parameters of wing shape with the lift-drag ratio as the optimization objective. The bionic wings with and without optimization were compared with the flat wings with the same wingspan, wing area and wing type. Vortex Lattice Method and 3D-Panel were used for aerodynamic calculation under the same flight conditions to obtain the relationship between the lift coefficient, drag coefficient, lift-drag ratio of the wings and the Angle of attack, as well as the wing pressure, lift, viscosity and induced drag distribution, respectively. The results show that the bionic wing with optimization has excellent lift-drag characteristics. When the Angle of attack is 7 degrees, the lift coefficient, drag coefficient and lift-drag ratio of the bionic wing with optimization are 0.667, 0.025 and 26.768, respectively. Compared with the bionic wing without optimization and the rectangular wing, the lift-drag ratio increases by 5.71 and 7.87%, respectively.

Weigang An, Fuzhen Shi, Shibei He, Wei Wang, Hang Zhang, Liu Liu

Effect of Aspect Ratio on Wake Patterns and Thrust Characteristics of Pitching Wings

Recently, flapping wing has attracted much attention due to its potential application prospect in the design of bionic Micro Aerial Vehicles(MAVs). As one of simplified propulsors developed to understand the thrust generation mechanisms of flapping wing, the pitching wing did not raised enough concern in previous studies because of its relatively poor propulsion performance. In particular, the aspect ratio effect and its physical mechanism in thrust generation need to be further clarified. In this paper, three-dimensional numerical simulations on a rectangular wing operating in a pure pitching motion are carried out to investigate the effect of aspect ratio on the vortex structures and thrust performance. For the governing parameters considered, the results indicate that both thrust and the critical Strouhal number(St) of drag-to-thrust transition are not significantly affected by the aspect ratio until St is beyond about 0.5, after which a greater thrust can be acquired for a higher aspect ratio. It’s believed that there exists a critical aspect ratio corresponding to the transition from the bifurcation wake to the deflection wake, above which the effect of aspect ratio on vortex structures can be neglected. To reveal the underlying mechanism of aspect ratio effect, a force estimation method based on finite control volume is used to establish a relationship between flow field and thrust. Three flow mechanisms are found that are responsible for the aspect ratio effect on thrust generation: for a higher aspect ratio, a more intense momentum surplus field and a more intense vorticity field are the mechanisms that generate greater thrust while a more pressure reduction field is the mechanism that generates greater drag. The aspect ratio effect on thrust generation actually results from the competition of these flow mechanisms. This work is expected to improve awareness for principles of flapping-wing propulsion.

Dechuan Ma, Zhan Qiu, Gaohua Li, Fuxin Wang

Research on Negative Turbulent Kinetic Energy Production in Supersonic Channel Flow

The anomaly of the energy reverse transmission process makes the turbulent kinetic energy production term in the turbulent kinetic energy transport equation negative. The negative production of turbulent kinetic energy (NPTKE) will affect the redistribution of energy in the flow field, and the conventional gradient assumption is not applicable in many flow situations. In this paper, the Reynolds stress turbulence model is used to solve the two-dimensional compressible turbulent kinetic energy transport equation. The commercial software Fluent v19.1 is utilized to numerically simulate the supersonic channel flow with the effect of shock waves. The results indicate that the Reynolds stress model considering flow anisotropy can characterize the NPTKE. The inherent properties of the mean strain rate tensor influence the turbulent kinetic energy production, and the NPTKE is dominated by the stretching factors. The compression caused by the shock wave leads to a constant positive turbulent kinetic energy production at the position, and the local maximum value is approximately obtained.

Hang Zhou, Fang Chen

Design and Experimental Study of Automatic Docking and Undocking Robot System for Launch Vehicle Propellant Filling

An automatic docking and undocking robot system was designed for the propellant filling process before the launch of the launch vehicle, instead of manually completing the filling operation. This filling robot system consists of a robot body, a control system and a positioning system. The robot body includes a base, a SCARA manipulator and a gentle docking and withdrawal system. The SCARA manipulator is coordinated to achieve the positioning and tracking of the rocket filling port through the control system and the positioning system, and then the gentle docking and withdrawal system completes the docking of the fill-drain connector and the rocket filling port as the robot’s execution end. The positioning system mainly uses a lidar system, which detects the target board to achieve positioning and tracking based on artificial beacons, and uses the arithmetic mean method to perform error compensation. Finally, a large number of experimental studies verify the reliability and stability of the robot system.

Jiawei You, Yue Huang, Xiangming Dun

Adaptive Fading Factor Unscented Kalman Filter with Application to Target Tracking

One purpose of target tracking is to estimate the states of targets, and Unscented Kalman filter(UKF) is one of the effective algorithms for estimating in the nonlinear tracking problem. Considering the characteristics of complex maneuverability, it is easy to reduce the tracking accuracy and cause divergence due to the mismatch between the system model and the practical target motion-model. Adaptive fading factor is an effective counter to this problem, having been instrumental in solving accuracy and divergence problems. Fading factor can adaptively adjust covariance matrix online to compensate model mismatch error. Moreover, fading factor not only improves the filtering accuracy, but also automatically adjusts the error covariance in response to the different situation. The simulation results show that the adaptive fading factor Unscented Kalman filter(AFUKF) has more advantages in target tracking and it can be better applied to nonlinear target tracking.

Peng Gu, Zhongliang Jing, Liangbin Wu

A Function Analysis Methodology Applied in Civil Aircraft Design

The functions and requirements play an extremely important role in developing complex systems nowadays. In this paper. A Function Analysis Methodology applied in a civil aircraft program is introduced. The function identification, organization and characterization processes of for a civil aircraft air management system are presented in detail. Furthermore, a function priority approach is taken into consideration. It shows that it is effective to perform functional analysis process to provides benefits to aircraft design: it discourages single-point solutions, and it describes the behaviors that lead to requirements and physical architectures. Function Analysis Methodology provides aircraft system with a functional system description that becomes a framework for developing requirements and physical architectures, and it significantly improves synthesis of design and integration.

Chao Tang, Xinai Zhang, Haomin Li, Dongsheng Chen, Jian Wang, Yong Chen
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