Transactions of Nanjing University of Aeronautics & Astronautics
Volume 35,Issue S1,2018 Table of Contents
2018, 35(S1):1-8.
DOI: 10.16356/j.1005-1120.2018.S.001
Abstract:
With the wider use of UAV in various fields, the raising task complexity and the increasing environmental uncertainties, the higher requirements for UAV technology are put forward. The bionic UAV cluster system has the potential advantages of good stealth performance, strong environmental adaptability, wide expansion of task and high operational efficiency. It has excellent prospects in future information warfare, electronic warfare and conventional combat field. By reviewing the development of bionic UAV cluster technology, this paper summarizes and analyzes the latest research progresses of the key technologies such as aerodynamic mechanism and aerodynamic configuration design, driving mechanism design, autonomous flight control, adaptive networking and cluster control of bionic aircrafts.
With the wider use of UAV in various fields, the raising task complexity and the increasing environmental uncertainties, the higher requirements for UAV technology are put forward. The bionic UAV cluster system has the potential advantages of good stealth performance, strong environmental adaptability, wide expansion of task and high operational efficiency. It has excellent prospects in future information warfare, electronic warfare and conventional combat field. By reviewing the development of bionic UAV cluster technology, this paper summarizes and analyzes the latest research progresses of the key technologies such as aerodynamic mechanism and aerodynamic configuration design, driving mechanism design, autonomous flight control, adaptive networking and cluster control of bionic aircrafts.
2018, 35(S1):9-15.
DOI: 10.16356/j.1005-1120.2018.S.009
Abstract:
In order to study component matching which exists in off-design situation at the initial design stage of turbine engine, by establishing performance analysis model of low bypass ratio mixed flow turbofan engine and components characteristic data, and by applying Newton-Raphson method to solve the nonlinear equations of off-design points in flying envelop, the factors which affect matching between engine components are studied. The results show that low pressure turbine (LPT) must not operate in a critical condition, and the partial derivative (slope) of pressure ratio to similitude mass flow ratio of working point in LPT characteristic map affects the stability of engine. The smaller the slope is, the more stable the engine is. In addition, the engine is more stable when the fan characteristic map is steep.
In order to study component matching which exists in off-design situation at the initial design stage of turbine engine, by establishing performance analysis model of low bypass ratio mixed flow turbofan engine and components characteristic data, and by applying Newton-Raphson method to solve the nonlinear equations of off-design points in flying envelop, the factors which affect matching between engine components are studied. The results show that low pressure turbine (LPT) must not operate in a critical condition, and the partial derivative (slope) of pressure ratio to similitude mass flow ratio of working point in LPT characteristic map affects the stability of engine. The smaller the slope is, the more stable the engine is. In addition, the engine is more stable when the fan characteristic map is steep.
2018, 35(S1):16-19.
DOI: 10.16356/j.1005-1120.2018.S.016
Abstract:
Numerical simulation is carried out for jets arranged at 7 different positions for the same model and compared with non-jet flows. The total and rudder force and moment amplification is calculated and analyzed by the pressure distribution on the surface and rudders of the simplified missile. Numerical results show that interactions take great effect on the configuration of the flow field around rudders and the pressure distribution on the missile surface.
Numerical simulation is carried out for jets arranged at 7 different positions for the same model and compared with non-jet flows. The total and rudder force and moment amplification is calculated and analyzed by the pressure distribution on the surface and rudders of the simplified missile. Numerical results show that interactions take great effect on the configuration of the flow field around rudders and the pressure distribution on the missile surface.
2018, 35(S1):20-26.
DOI: 10.16356/j.1005-1120.2018.S.020
Abstract:
Considering the existence of multi-level fares in the alliance, and the existence of horizontal competition and vertical competition at the same time, this paper intends to maximize the revenue of airline alliance and fairly distribute the revenue to member airlines. Firstly, a model is built under the centralized mechanism, in which all airlines in the alliance are regarded as a whole. By solving the model, the shadow price of each flight leg on the code-sharing route is gotten. It is used to calculate the proportion of the revenue distribution. Then, the centralized model is decomposed into the single airline model by the proportion. The seat allocation among airlines and distributed revenue can be gotten by solving the model. Three typical examples are designed to test it. The results show that, the model can effectively reflect the managerial principal of the airline alliance, that is maximizing total revenue and fairly distributing the revenue among member airlines.
Considering the existence of multi-level fares in the alliance, and the existence of horizontal competition and vertical competition at the same time, this paper intends to maximize the revenue of airline alliance and fairly distribute the revenue to member airlines. Firstly, a model is built under the centralized mechanism, in which all airlines in the alliance are regarded as a whole. By solving the model, the shadow price of each flight leg on the code-sharing route is gotten. It is used to calculate the proportion of the revenue distribution. Then, the centralized model is decomposed into the single airline model by the proportion. The seat allocation among airlines and distributed revenue can be gotten by solving the model. Three typical examples are designed to test it. The results show that, the model can effectively reflect the managerial principal of the airline alliance, that is maximizing total revenue and fairly distributing the revenue among member airlines.
2018, 35(S1):27-34.
DOI: 10.16356/j.1005-1120.2018.S.027
Abstract:
A wearable passive exoskeleton is proposed for reduced gravity astronauts training. The main component unit of the proposed robotic exoskeleton is the spring-based parallelogram mechanism which can passively balance any proportion of the gravity load acting on it through designing an appropriate stiffness of the spring or adjusting the install position of the spring. A conceptual exoskeleton model capable of gravity compensation for upper limbs applying to such technology is designed and the corresponding simulation is presented, in which the muscle activations are collected to show the effectiveness of the design.
A wearable passive exoskeleton is proposed for reduced gravity astronauts training. The main component unit of the proposed robotic exoskeleton is the spring-based parallelogram mechanism which can passively balance any proportion of the gravity load acting on it through designing an appropriate stiffness of the spring or adjusting the install position of the spring. A conceptual exoskeleton model capable of gravity compensation for upper limbs applying to such technology is designed and the corresponding simulation is presented, in which the muscle activations are collected to show the effectiveness of the design.
2018, 35(S1):35-40.
DOI: 10.16356/j.1005-1120.2018.S.035
Abstract:
The current research on gas film is mainly in various precision instruments and machinery while the studies on gas film in ultrasonic motor is few. Based on original N-S equations, the mechanism of gas film action in traveling wave rotary ultrasonic motor (TRUM) is explored through physical explanations and analyzed through numerical simulation. Pressure distributions in the smooth gas film and the gas film considering stator teeth are analyzed. It is concluded that the squeeze number and the non-dimensional amplitude are the main factors that affect the pressure distribution. As the approximate region becomes smaller, the pressure peak of the smooth gas film is close to an atmosphere. The pressure on tooth region is the same as that on smooth model while the region between teeth affects weakly on the whole model.
The current research on gas film is mainly in various precision instruments and machinery while the studies on gas film in ultrasonic motor is few. Based on original N-S equations, the mechanism of gas film action in traveling wave rotary ultrasonic motor (TRUM) is explored through physical explanations and analyzed through numerical simulation. Pressure distributions in the smooth gas film and the gas film considering stator teeth are analyzed. It is concluded that the squeeze number and the non-dimensional amplitude are the main factors that affect the pressure distribution. As the approximate region becomes smaller, the pressure peak of the smooth gas film is close to an atmosphere. The pressure on tooth region is the same as that on smooth model while the region between teeth affects weakly on the whole model.
2018, 35(S1):41-45.
DOI: 10.16356/j.1005-1120.2018.S.041
Abstract:
Because of having millions of well vertically aligned hairs on their feet, geckos can fluently walk on the vertical walls and even ceilings. Vertically aligned carbon nanotube (VACNT) array has been widely used as a bio-mimetic adhesive due to the structural and functional similarity with gecko's foot hairs. Besides, the advanced properties of VACNT make it a prominent functional adhesive. In this paper, the dry adhesion of VACNT array under the temperature range of 25-150℃ is studied. Because of the intrinsic excellent thermal resistance, VACNT array shows great adhesion under high temperature. When the temperature changes from 25℃ to 150℃, the shear adhesive strength of VACNT array deceases from 12.04 N/cm2 to 6.08 N/cm2. Though there is a 50 percent decrease, the adhesive strength of 6.08 N/cm2 is still remarkable for dry adhesive materials. The VACNT's micro structures are analyzed by SEM and the adhesion change phenomenon is interpreted in theory. We believe that the robust high temperature adaptation of VACNT dry adhesive can be used in many extreme environments, such as aerospace application.
Because of having millions of well vertically aligned hairs on their feet, geckos can fluently walk on the vertical walls and even ceilings. Vertically aligned carbon nanotube (VACNT) array has been widely used as a bio-mimetic adhesive due to the structural and functional similarity with gecko's foot hairs. Besides, the advanced properties of VACNT make it a prominent functional adhesive. In this paper, the dry adhesion of VACNT array under the temperature range of 25-150℃ is studied. Because of the intrinsic excellent thermal resistance, VACNT array shows great adhesion under high temperature. When the temperature changes from 25℃ to 150℃, the shear adhesive strength of VACNT array deceases from 12.04 N/cm2 to 6.08 N/cm2. Though there is a 50 percent decrease, the adhesive strength of 6.08 N/cm2 is still remarkable for dry adhesive materials. The VACNT's micro structures are analyzed by SEM and the adhesion change phenomenon is interpreted in theory. We believe that the robust high temperature adaptation of VACNT dry adhesive can be used in many extreme environments, such as aerospace application.
2018, 35(S1):46-50.
DOI: 10.16356/j.1005-1120.2018.S.046
Abstract:
A novel fiber temperature sensor based on multimode interference theory is proposed and experimentally demonstrated. The sensing head is formed by a fiber bragg grating (FBG) connected with single-mode-no core-single-mode fiber(SNS) fiber structure which consists of two sections of single mode fiber and no-core fiber.Using such a structure, not only the reflective measurement can be realized, but also the need for a gold-plated film can be avoided at the end of the fiber to enhance the reflected light signal. More importantly, the sensitivity is increased by 4 times as compared with the conventional FBG temperature sensor according to the experimental results, and it also provides the development space for multi-parameters monitoring.
A novel fiber temperature sensor based on multimode interference theory is proposed and experimentally demonstrated. The sensing head is formed by a fiber bragg grating (FBG) connected with single-mode-no core-single-mode fiber(SNS) fiber structure which consists of two sections of single mode fiber and no-core fiber.Using such a structure, not only the reflective measurement can be realized, but also the need for a gold-plated film can be avoided at the end of the fiber to enhance the reflected light signal. More importantly, the sensitivity is increased by 4 times as compared with the conventional FBG temperature sensor according to the experimental results, and it also provides the development space for multi-parameters monitoring.
2018, 35(S1):51-58.
DOI: 10.16356/j.1005-1120.2018.S.051
Abstract:
Super depth digital microscope was employed to observe the macro-/micro-structure of Coleoptera's elytra. The non-smooth surface textures of elytra have shown superior performance of friction reduction and lubrication. Bionic models of regular hexagonal convex texture and circular concave texture inspired by the beetle were established and verified by numerical calculations and simulations. Further tribological experiments were performed and the results show that the circle texture has the lowest coefficient, which is consistent with the numerical calculations. The research may be further applied to new bionic surface texture designs and also work as a biological template for new bionic inventions.
Super depth digital microscope was employed to observe the macro-/micro-structure of Coleoptera's elytra. The non-smooth surface textures of elytra have shown superior performance of friction reduction and lubrication. Bionic models of regular hexagonal convex texture and circular concave texture inspired by the beetle were established and verified by numerical calculations and simulations. Further tribological experiments were performed and the results show that the circle texture has the lowest coefficient, which is consistent with the numerical calculations. The research may be further applied to new bionic surface texture designs and also work as a biological template for new bionic inventions.
2018, 35(S1):59-62.
DOI: 10.16356/j.1005-1120.2018.S.059
Abstract:
Pilot plays an essential role in a duplex communication system. Several methods have been proposed for pilot assignment over specific scenarios. With the help of permutation encoding, we implemented a genetic algorithm for optimizing pilot assignment in a multi-user massive multiple input multiple output (MIMO) system. Results show improvement on existing results especially in the case of strong user estimation rates.
Pilot plays an essential role in a duplex communication system. Several methods have been proposed for pilot assignment over specific scenarios. With the help of permutation encoding, we implemented a genetic algorithm for optimizing pilot assignment in a multi-user massive multiple input multiple output (MIMO) system. Results show improvement on existing results especially in the case of strong user estimation rates.
2018, 35(S1):63-67.
DOI: 10.16356/j.1005-1120.2018.S.063
Abstract:
Traditional plastic scintillator has respectively low gamma energy resolution. Space radiation detection need the plastic scintillator to keep a relatively better energy resolution for gamma. Thus we did experiments to study how to get it enhanced by adding light guider and chamfer. A 9000Bq radioactive source 60Co has been utilized to make the experiment and results came that when keeping other conditions same, the height of poly methyl methacrylate (PMMA) light guider changes from 12mm to 40mm and the energy resolutions varied from 72.3% to 63.5% respectively. Furthermore, another contrast experiment was made to decide whether plastic scintillator with light guiders or integrated chamfer can get better energy resolution. In conclusion the plastic scintillator with integrated chamfer got 55.0%. Through the study of adding light guider or chamfer to plastic scintillator, the gamma energy resolution has been improved greatly from 72.3% to 55.0%.
Traditional plastic scintillator has respectively low gamma energy resolution. Space radiation detection need the plastic scintillator to keep a relatively better energy resolution for gamma. Thus we did experiments to study how to get it enhanced by adding light guider and chamfer. A 9000Bq radioactive source 60Co has been utilized to make the experiment and results came that when keeping other conditions same, the height of poly methyl methacrylate (PMMA) light guider changes from 12mm to 40mm and the energy resolutions varied from 72.3% to 63.5% respectively. Furthermore, another contrast experiment was made to decide whether plastic scintillator with light guiders or integrated chamfer can get better energy resolution. In conclusion the plastic scintillator with integrated chamfer got 55.0%. Through the study of adding light guider or chamfer to plastic scintillator, the gamma energy resolution has been improved greatly from 72.3% to 55.0%.
2018, 35(S1):68-74.
DOI: 10.16356/j.1005-1120.2018.S.068
Abstract:
An improved particle swarm optimization(PSO) algorithm based on dynamic inertia weight and adjustment coefficient is proposed in this paper. The expressions of inertia weight and adjustment coefficient are established based on inter-particle distance and iterations. The improved algorithm is applied to a novel two-stage photovoltaic(PV) converter. The later DC/AC circuit chooses a dual-DC-input multi-level dual-buck inverter. This converter has the advantages of no shoot-through problem and high efficiency. Finally, the validity and effectiveness of the algorithm and the converter are verified with experimental results.
An improved particle swarm optimization(PSO) algorithm based on dynamic inertia weight and adjustment coefficient is proposed in this paper. The expressions of inertia weight and adjustment coefficient are established based on inter-particle distance and iterations. The improved algorithm is applied to a novel two-stage photovoltaic(PV) converter. The later DC/AC circuit chooses a dual-DC-input multi-level dual-buck inverter. This converter has the advantages of no shoot-through problem and high efficiency. Finally, the validity and effectiveness of the algorithm and the converter are verified with experimental results.
2018, 35(S1):75-80.
DOI: 10.16356/j.1005-1120.2018.S.075
Abstract:
Synthetic aperture using moving array is widely used for extending array aperture and improving direction of arrival (DOA) estimation performance. This paper proposes a DOA estimation algorithm with non-uniform motion synthetic linear array. The proposed method successively estimates the phase correction factors of the signals received by a moving linear array and then compensates the manifold to construct a much larger synthetic array. With the synthetic array, the DOA estimation performance is efficiently improved. Besides, due to the successive phase correction factors estimation, the proposed method can be applied regardless of the configuration and motion of the linear array and can release the request of temporal signal coherence. The simulations validate the effectiveness of the proposed method.
Synthetic aperture using moving array is widely used for extending array aperture and improving direction of arrival (DOA) estimation performance. This paper proposes a DOA estimation algorithm with non-uniform motion synthetic linear array. The proposed method successively estimates the phase correction factors of the signals received by a moving linear array and then compensates the manifold to construct a much larger synthetic array. With the synthetic array, the DOA estimation performance is efficiently improved. Besides, due to the successive phase correction factors estimation, the proposed method can be applied regardless of the configuration and motion of the linear array and can release the request of temporal signal coherence. The simulations validate the effectiveness of the proposed method.
2018, 35(S1):81-87.
DOI: 10.16356/j.1005-1120.2018.S.081
Abstract:
This paper presents the design of a wireless building monitoring network implemented at the University of Nottingham's Creative Energy Homes test site. The network is installed in seven smart buildings with the aim of holistically collecting energy data. Data will be used to inform a central control algorithm to optimise the energy flows between buildings, in turn promoting the smart cities concept. Sensors and meters measuring temperature, humidity, CO2, heat energy, power, and stratified tank temperature are described. Furthermore, the communication protocols utilised are also discussed, which include wireless MBus and EnOcean. This paper also covers the methods used for ensuring the reliability of data signals and the system controls.
This paper presents the design of a wireless building monitoring network implemented at the University of Nottingham's Creative Energy Homes test site. The network is installed in seven smart buildings with the aim of holistically collecting energy data. Data will be used to inform a central control algorithm to optimise the energy flows between buildings, in turn promoting the smart cities concept. Sensors and meters measuring temperature, humidity, CO2, heat energy, power, and stratified tank temperature are described. Furthermore, the communication protocols utilised are also discussed, which include wireless MBus and EnOcean. This paper also covers the methods used for ensuring the reliability of data signals and the system controls.
2018, 35(S1):88-95.
DOI: 10.16356/j.1005-1120.2018.S.088
Abstract:
In this paper, contribution of sources to the efficiency of Turkish investment trust companies is investigated by eight models which are constructed by different combinations of inputs of DEA analyze structure. Input oriented CRS based data envelopment analysis (DEA) and also Malmquist Productivity Index are applied for the time period of 2009—2016. Inputs of the CRS model are preferred as financial investments, cash and cash equivalents, cost of sales, and total sales while net profit and net sales are outputs of the models. It is reached at the conclusion that only management of investments is providing better results than only focusing on cash or cost management. In addition, effects and contribution of investment management parameter when it is added to the other ones is found more.
In this paper, contribution of sources to the efficiency of Turkish investment trust companies is investigated by eight models which are constructed by different combinations of inputs of DEA analyze structure. Input oriented CRS based data envelopment analysis (DEA) and also Malmquist Productivity Index are applied for the time period of 2009—2016. Inputs of the CRS model are preferred as financial investments, cash and cash equivalents, cost of sales, and total sales while net profit and net sales are outputs of the models. It is reached at the conclusion that only management of investments is providing better results than only focusing on cash or cost management. In addition, effects and contribution of investment management parameter when it is added to the other ones is found more.
2018, 35(S1):96-102.
DOI: 10.16356/j.1005-1120.2018.S.096
Abstract:
Based on the phenomenon of "split brick by Qigong", a mechanical model for short beam impact is proposed. Combined with the traditional energy method, a theoretical analysis of the impact of the short beam (Timoshenko beam) closer to the real situation is made considering the quality and initial deformation. The optimal solution of short beam impact problem of how to choose the position where the short beam is most likely to break is obtained. The finite element numerical analysis and experimental test are used, and the results verify the applicability of the theoretical analysis of the proposed model.
Based on the phenomenon of "split brick by Qigong", a mechanical model for short beam impact is proposed. Combined with the traditional energy method, a theoretical analysis of the impact of the short beam (Timoshenko beam) closer to the real situation is made considering the quality and initial deformation. The optimal solution of short beam impact problem of how to choose the position where the short beam is most likely to break is obtained. The finite element numerical analysis and experimental test are used, and the results verify the applicability of the theoretical analysis of the proposed model.
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