Transactions of Nanjing University of Aeronautics & Astronautics
Volume 35,Issue 4,2018 Table of Contents
2018, 35(4):565-577.
DOI: 10.16356/j.1005-1120.2018.04.565
Abstract:
Secondary lithium-sulfur batteries have attracted extensive attention due to their high energy density, low cost and environment friendly. However, the "shuttle effect" of polysulfides dissolved in liquid electrolytes leads to a decrease of the cell Coulomb efficiency (CE). Therefore, researchers have used solid electrolytes instead of traditional liquid electrolytes and separators to suppress the "shuttle effect" of polysulfides and the growth of lithium dendrites. The progress in electrolytes for solid-state lithium-sulfur batteries including solid-state polymer, inorganic, and composite electrolytes to solve the issues is summarized.
Secondary lithium-sulfur batteries have attracted extensive attention due to their high energy density, low cost and environment friendly. However, the "shuttle effect" of polysulfides dissolved in liquid electrolytes leads to a decrease of the cell Coulomb efficiency (CE). Therefore, researchers have used solid electrolytes instead of traditional liquid electrolytes and separators to suppress the "shuttle effect" of polysulfides and the growth of lithium dendrites. The progress in electrolytes for solid-state lithium-sulfur batteries including solid-state polymer, inorganic, and composite electrolytes to solve the issues is summarized.
2018, 35(4):578-589.
DOI: 10.16356/j.1005-1120.2018.04.578
Abstract:
All solid state lithium battery is a promising next-generation battery system with improved cycle life, energy density, especially safety. However, its development is greatly hampered by a large impedance between the solid state electrolyte/electrode interface. How to build an ideal electrolyte/electrode interface to improve the interfacial stability and reduce the interfacial resistance is a huge challenge for improving battery performance. This paper reviews interfacial problems and introduces the formation mechanism of different interface layers between electrodes and electrolytes. In addition, the strategies for improving interfacial contact and reducing interfacial resistance are described in detail. Finally, the research directions for engineering interfaces in all solid state lithium batteries are proposed.
All solid state lithium battery is a promising next-generation battery system with improved cycle life, energy density, especially safety. However, its development is greatly hampered by a large impedance between the solid state electrolyte/electrode interface. How to build an ideal electrolyte/electrode interface to improve the interfacial stability and reduce the interfacial resistance is a huge challenge for improving battery performance. This paper reviews interfacial problems and introduces the formation mechanism of different interface layers between electrodes and electrolytes. In addition, the strategies for improving interfacial contact and reducing interfacial resistance are described in detail. Finally, the research directions for engineering interfaces in all solid state lithium batteries are proposed.
2018, 35(4):590-602.
DOI: 10.16356/j.1005-1120.2018.04.590
Abstract:
Three-dimensional (3D) carbon networks have been explored as promising capacitive materials thanks to their unique structural features such as large ion-accessible surface area and interconnected porous networks, thus enhancing both ions and electrons transport. Here, sustainable bacterial cellulose (BC) is used both precursor and template for facile synthesis of free-standing N, S-codoped 3D carbon networks (a-NSC) by the pyrolysis and activation of polyrhodanine coated BC. The synthesized a-NSC shows highly conductive interconnected porous networks (24 S·cm-1), large surface area (1 420 m2·g-1) with hierarchical meso-microporosity, and high-level heteroatoms codoping (N:3.1% in atom, S:3.2% in atom). Benefitting from these, a-NSC as binder-free electrode exhibits an ultrahigh specific capacitance of 340 F·g-1 (24 μF·cm-2) at the current density of 0.5 A·g-1 in 6 M KOH electrolyte, high-rate capability (71% at 20 A·g-1) and excellent cycle stability. Furthermore, the assembled symmetrical supercapacitor displays a much short time constant of 0.35 s in 1 M TEABF4/AN electrolyte, obtaining a maximum energy density of 32.1 W·h·kg-1 at power density of 637 W·kg-1. The in situ multi-heteroatoms doping enables biocellulose-derived carbon networks to exploit its full potentials in energy storage applications, which can be extended to other dimensional carbon nanostructures.
Three-dimensional (3D) carbon networks have been explored as promising capacitive materials thanks to their unique structural features such as large ion-accessible surface area and interconnected porous networks, thus enhancing both ions and electrons transport. Here, sustainable bacterial cellulose (BC) is used both precursor and template for facile synthesis of free-standing N, S-codoped 3D carbon networks (a-NSC) by the pyrolysis and activation of polyrhodanine coated BC. The synthesized a-NSC shows highly conductive interconnected porous networks (24 S·cm-1), large surface area (1 420 m2·g-1) with hierarchical meso-microporosity, and high-level heteroatoms codoping (N:3.1% in atom, S:3.2% in atom). Benefitting from these, a-NSC as binder-free electrode exhibits an ultrahigh specific capacitance of 340 F·g-1 (24 μF·cm-2) at the current density of 0.5 A·g-1 in 6 M KOH electrolyte, high-rate capability (71% at 20 A·g-1) and excellent cycle stability. Furthermore, the assembled symmetrical supercapacitor displays a much short time constant of 0.35 s in 1 M TEABF4/AN electrolyte, obtaining a maximum energy density of 32.1 W·h·kg-1 at power density of 637 W·kg-1. The in situ multi-heteroatoms doping enables biocellulose-derived carbon networks to exploit its full potentials in energy storage applications, which can be extended to other dimensional carbon nanostructures.
2018, 35(4):603-610.
DOI: 10.16356/j.1005-1120.2018.04.603
Abstract:
The high performance of an electrode relies largely on a scrupulous design of nanoarchitectures and smart hybridization of electroactive materials. A porous core-shell architecture in which one-dimensional cobalt oxide (Co3O4) nanowire cores are grown on nickel foam prior to the growth of layered double hydroxide (LDH) shells is fabricated. Hydrothermal precipitation and thermal treatment result in homogeneous forests of 70-nm diameter Co3O4 nanowire, which are wrapped in LDH-nanosheet-built porous covers through a liquid phase deposition method. Due to the unique core-shell architecture and the synergetic effects of Co3O4 and NiAl-LDH, the obtained Co3O4@LDH electrode exhibits a capacitance of 1 133.3 F/g at a current density of 2 A/g and 688.8 F/g at 20 A/g (5.3 F/cm2 at 9.4 mA/cm2 and 3.2 F/cm2 at 94 mA/cm2), which are better than those of the individual Co3O4 nanowire. Moreover, the electrode shows excellent cycling performance with a retention rate of 90.4% after 3 000 cycles at a current density of 20 A/g.
The high performance of an electrode relies largely on a scrupulous design of nanoarchitectures and smart hybridization of electroactive materials. A porous core-shell architecture in which one-dimensional cobalt oxide (Co3O4) nanowire cores are grown on nickel foam prior to the growth of layered double hydroxide (LDH) shells is fabricated. Hydrothermal precipitation and thermal treatment result in homogeneous forests of 70-nm diameter Co3O4 nanowire, which are wrapped in LDH-nanosheet-built porous covers through a liquid phase deposition method. Due to the unique core-shell architecture and the synergetic effects of Co3O4 and NiAl-LDH, the obtained Co3O4@LDH electrode exhibits a capacitance of 1 133.3 F/g at a current density of 2 A/g and 688.8 F/g at 20 A/g (5.3 F/cm2 at 9.4 mA/cm2 and 3.2 F/cm2 at 94 mA/cm2), which are better than those of the individual Co3O4 nanowire. Moreover, the electrode shows excellent cycling performance with a retention rate of 90.4% after 3 000 cycles at a current density of 20 A/g.
2018, 35(4):611-618.
DOI: 10.16356/j.1005-1120.2018.04.611
Abstract:
Fossil fuel exhaustion and overdevelopment usually lead to a recession, which is worsened by the environmental pollution. So it is of high priority to develop high-efficiency energy storage device. Here, a green and environment-friendly strategy is devised to fabricate carbon materials from biomass. By water extraction and alcohol precipitation, polysaccharide is extracted from loquat leaves. After calcining under high temperature, hierarchical porous carbon materials (HPCM) are obtained, possessing a variety of macropores, mesopores and micropores. Such ample and hierarchical pores enable the electrolyte infiltration and the buffering of the volume expansion of sulfur in repeated electrochemical reactions. The structure stability of the entire electrode can thus be well maintained. When evaluated as the scaffold for sulfur, the electrochemical performance of carbon/sulfur composite was tested. Even after 500 cycles, the reversible capacity is retained as high as 485.4 mA·h/g at the current density of 1.6 A/g. It also offers a notable rate capability, attaining the discharge capacity of 700.7 mA·h/g at 2 C. All the electrochemical performance results prove the feasibility of the proposed strategy.
Fossil fuel exhaustion and overdevelopment usually lead to a recession, which is worsened by the environmental pollution. So it is of high priority to develop high-efficiency energy storage device. Here, a green and environment-friendly strategy is devised to fabricate carbon materials from biomass. By water extraction and alcohol precipitation, polysaccharide is extracted from loquat leaves. After calcining under high temperature, hierarchical porous carbon materials (HPCM) are obtained, possessing a variety of macropores, mesopores and micropores. Such ample and hierarchical pores enable the electrolyte infiltration and the buffering of the volume expansion of sulfur in repeated electrochemical reactions. The structure stability of the entire electrode can thus be well maintained. When evaluated as the scaffold for sulfur, the electrochemical performance of carbon/sulfur composite was tested. Even after 500 cycles, the reversible capacity is retained as high as 485.4 mA·h/g at the current density of 1.6 A/g. It also offers a notable rate capability, attaining the discharge capacity of 700.7 mA·h/g at 2 C. All the electrochemical performance results prove the feasibility of the proposed strategy.
2018, 35(4):619-629.
DOI: 10.16356/j.1005-1120.2018.04.619
Abstract:
Though water electrolysis is effective in generating high-quality hydrogen gas, it requires effective electrocatalysts for hydrogen evolution reaction (HER). CoS2 have been considered as a promising HER electrocatalyst because of its high ctalytic activity. However, the key limitation for CoS2 nanomaterial as HER electrocatalyst is its poor stability, which may be due to the structural breakdown of CoS2 nanostructure or the evolution of S during H2 evolution in acid media. Coating porous carbon thin layer for protection from structural breakdown and evolution of S is a good way to improve catalytic stability. In addition, coating carbon layer can change electronic structure of CoS2 for the moderated hydrogen adsorption energy, leading to enhanced catalytic activity. Here, CoS2 yolk-shell spheres coated with carbon thin layers exhibit superior catalytic performance for HER with low overpotential, small Tafel slope, and excellent stability.
Though water electrolysis is effective in generating high-quality hydrogen gas, it requires effective electrocatalysts for hydrogen evolution reaction (HER). CoS2 have been considered as a promising HER electrocatalyst because of its high ctalytic activity. However, the key limitation for CoS2 nanomaterial as HER electrocatalyst is its poor stability, which may be due to the structural breakdown of CoS2 nanostructure or the evolution of S during H2 evolution in acid media. Coating porous carbon thin layer for protection from structural breakdown and evolution of S is a good way to improve catalytic stability. In addition, coating carbon layer can change electronic structure of CoS2 for the moderated hydrogen adsorption energy, leading to enhanced catalytic activity. Here, CoS2 yolk-shell spheres coated with carbon thin layers exhibit superior catalytic performance for HER with low overpotential, small Tafel slope, and excellent stability.
2018, 35(4):630-638.
DOI: 10.16356/j.1005-1120.2018.04.630
Abstract:
Polyaniline (PANI) was effectively immobilized on the surface of ordered mesoporous carbon (OMC) by using Mn2O3 as sacrificial template. The observed microstructure and morphology indicate that a thin layer of PANI was coated on OMC uniformly. As a supercapacitor electrode material, the discharge capacity of the optimized PANI/OMC could reach 467 F/g, which is far higher than that of OMC, PANI and Mn2O3/OMC. Furthermore, PANI/OMC composites with different content of PANI are obtained by adjusting the amount of Mn2O3 on OMC and their properties are characterized. The results show that a thin layer of PANI can improve the capacity of PANI/OMC composites effectively and the further increase of PANI reduces the capacity of PANI/OMC composites. The sacrificial template method presented here is beneficial to coating a layer of polymer on carbon materials, and the content of polymer layer can be controlled by adjusting the amount of Mn2O3 in Mn2O3/OMC.
Polyaniline (PANI) was effectively immobilized on the surface of ordered mesoporous carbon (OMC) by using Mn2O3 as sacrificial template. The observed microstructure and morphology indicate that a thin layer of PANI was coated on OMC uniformly. As a supercapacitor electrode material, the discharge capacity of the optimized PANI/OMC could reach 467 F/g, which is far higher than that of OMC, PANI and Mn2O3/OMC. Furthermore, PANI/OMC composites with different content of PANI are obtained by adjusting the amount of Mn2O3 on OMC and their properties are characterized. The results show that a thin layer of PANI can improve the capacity of PANI/OMC composites effectively and the further increase of PANI reduces the capacity of PANI/OMC composites. The sacrificial template method presented here is beneficial to coating a layer of polymer on carbon materials, and the content of polymer layer can be controlled by adjusting the amount of Mn2O3 in Mn2O3/OMC.
2018, 35(4):639-647.
DOI: 10.16356/j.1005-1120.2018.04.639
Abstract:
The hierarchical porous N/O co-functionalized carbon (HPNOC) was scalably prepared by using the low-cost and renewable blighted grains as the raw material coupled with mild KHCO3 activation for electrochemical capacitors (ECs). The elemental N was in situ doped in the obtained HPNOC without any N-containing additives. Remarkably, the obtained HPNOC was endowed with a large specific surface area (about 2624 m2·g-1), high pore volume (about 1.35 cm3·g-1), as well as high-content N/O functionalization (about 1.9% (in atom) N and about 10.2% (in atom) O. Furthermore, the as-resulted HPNOC electrode with a high mass loading of 5 mg·cm-2 exhibited competitive gravimetric capacitances of about 373.6 F·g-1 at 0.5 A·g-1, and even about 260.4 F·g-1 at a high rate of 10 A·g-1; superior capacitance retention of about 98.8% at 1 A·g-1 over 10 000 consecutive cycles; and high specific energy of about 9.6 W·h·kg-1 at a power of 500 W·kg-1, when evaluated as a promising electrode in 6 mol KOH for advanced electrochemical supercapacitors. More encouragingly, the green synthetic strategy we developed holds a huge promise in generalizing for other biomass-derived carbon materials for versatile energy-related applications.
The hierarchical porous N/O co-functionalized carbon (HPNOC) was scalably prepared by using the low-cost and renewable blighted grains as the raw material coupled with mild KHCO3 activation for electrochemical capacitors (ECs). The elemental N was in situ doped in the obtained HPNOC without any N-containing additives. Remarkably, the obtained HPNOC was endowed with a large specific surface area (about 2624 m2·g-1), high pore volume (about 1.35 cm3·g-1), as well as high-content N/O functionalization (about 1.9% (in atom) N and about 10.2% (in atom) O. Furthermore, the as-resulted HPNOC electrode with a high mass loading of 5 mg·cm-2 exhibited competitive gravimetric capacitances of about 373.6 F·g-1 at 0.5 A·g-1, and even about 260.4 F·g-1 at a high rate of 10 A·g-1; superior capacitance retention of about 98.8% at 1 A·g-1 over 10 000 consecutive cycles; and high specific energy of about 9.6 W·h·kg-1 at a power of 500 W·kg-1, when evaluated as a promising electrode in 6 mol KOH for advanced electrochemical supercapacitors. More encouragingly, the green synthetic strategy we developed holds a huge promise in generalizing for other biomass-derived carbon materials for versatile energy-related applications.
2018, 35(4):648-655.
DOI: 10.16356/j.1005-1120.2018.04.648
Abstract:
The emergence of perovskite solar cells (PSCs) based on all-inorganic metal halide (IMH) has generated enormous interest in the photovoltaic research community, and the power conversion efficiency (PCE) has exceeded 13%. Despite its outstanding performance in thermal stability, PSCs based on IMH still face problems such as the lack of a suitable band gap and the inability to generate large areas. In this review, we will summarize the latest progress of PSCs based on IMH.
The emergence of perovskite solar cells (PSCs) based on all-inorganic metal halide (IMH) has generated enormous interest in the photovoltaic research community, and the power conversion efficiency (PCE) has exceeded 13%. Despite its outstanding performance in thermal stability, PSCs based on IMH still face problems such as the lack of a suitable band gap and the inability to generate large areas. In this review, we will summarize the latest progress of PSCs based on IMH.
2018, 35(4):656-663.
DOI: 10.16356/j.1005-1120.2018.04.656
Abstract:
Energy efficiency (EE) of downlink distributed antenna system (DAS) with multiple receive antennas is investigated over composite Rayleigh fading channel that takes the path loss and lognormal shadow fading into account. Our aim is to maximize EE which is defined as the ratio of the transmission rate to the total consumed power under the constraints of the maximum transmit power of each remote antenna. According to the definition of EE, the optimized objective function is formulated with the help of Lagrangian method. By using the Karush-Kuhn-Tucker (KKT) conditions and numerical calculation, considering both the static and dynamic circuit power consumptions, an adaptive energy efficient power allocation (PA) scheme is derived. This scheme is different from the conventional iterative PA schemes based on EE maximization since it can provide closed-form expression of PA coefficients. Moreover, it can obtain the EE performance close to the conventional iterative scheme and exhaustive search method while reducing the computation complexity greatly. Simulation results verify the effectiveness of the proposed scheme.
Energy efficiency (EE) of downlink distributed antenna system (DAS) with multiple receive antennas is investigated over composite Rayleigh fading channel that takes the path loss and lognormal shadow fading into account. Our aim is to maximize EE which is defined as the ratio of the transmission rate to the total consumed power under the constraints of the maximum transmit power of each remote antenna. According to the definition of EE, the optimized objective function is formulated with the help of Lagrangian method. By using the Karush-Kuhn-Tucker (KKT) conditions and numerical calculation, considering both the static and dynamic circuit power consumptions, an adaptive energy efficient power allocation (PA) scheme is derived. This scheme is different from the conventional iterative PA schemes based on EE maximization since it can provide closed-form expression of PA coefficients. Moreover, it can obtain the EE performance close to the conventional iterative scheme and exhaustive search method while reducing the computation complexity greatly. Simulation results verify the effectiveness of the proposed scheme.
2018, 35(4):664-670.
DOI: 10.16356/j.1005-1120.2018.04.664
Abstract:
A multiple frequency cancellation (MFC) method is proposed for stealth design of ultra-wide band (UWB) end-fire antenna array. The proposed method can produce significant radar cross section (RCS) reduction in the whole operating band. The 1×4 and 4×4 Vivaldi antenna arrays of different kinds of cancellation structures are discussed as examples to validate the effectiveness of the MFC method on both linear and planar arrays. On average, 22.6 dB reduction of monostatic radar cross section (MRCS) is obtained in the whole X-band. MRCS under oblique incident waves is also reduced within ±60°. Basically favorable radiation characteristics are maintained.
A multiple frequency cancellation (MFC) method is proposed for stealth design of ultra-wide band (UWB) end-fire antenna array. The proposed method can produce significant radar cross section (RCS) reduction in the whole operating band. The 1×4 and 4×4 Vivaldi antenna arrays of different kinds of cancellation structures are discussed as examples to validate the effectiveness of the MFC method on both linear and planar arrays. On average, 22.6 dB reduction of monostatic radar cross section (MRCS) is obtained in the whole X-band. MRCS under oblique incident waves is also reduced within ±60°. Basically favorable radiation characteristics are maintained.
2018, 35(4):671-682.
DOI: 10.16356/j.1005-1120.2018.04.671
Abstract:
Many industrial products are normally processed through multiple manufacturing process stages before it becomes a final product. Statistical process control techniques often utilize standard Shewhart control charts to monitor these process stages. If the process stages are independent, this is a meaningful procedure. However, they are not independent in many manufacturing scenarios. The standard Shewhart control charts can not provide the information to determine which process stage or group of process stages has caused the problems (i.e., standard Shewhart control charts could not diagnose dependent manufacturing process stages). This study proposes a selective neural network ensemble-based cause-selecting system of control charts to monitor these process stages and distinguish incoming quality problems and problems in the current stage of a manufacturing process. Numerical results show that the proposed method is an improvement over the use of separate Shewhart control chart for each of dependent process stages, and even ordinary quality practitioners who lack of expertise in theoretical analysis can implement regression estimation and neural computing readily.
Many industrial products are normally processed through multiple manufacturing process stages before it becomes a final product. Statistical process control techniques often utilize standard Shewhart control charts to monitor these process stages. If the process stages are independent, this is a meaningful procedure. However, they are not independent in many manufacturing scenarios. The standard Shewhart control charts can not provide the information to determine which process stage or group of process stages has caused the problems (i.e., standard Shewhart control charts could not diagnose dependent manufacturing process stages). This study proposes a selective neural network ensemble-based cause-selecting system of control charts to monitor these process stages and distinguish incoming quality problems and problems in the current stage of a manufacturing process. Numerical results show that the proposed method is an improvement over the use of separate Shewhart control chart for each of dependent process stages, and even ordinary quality practitioners who lack of expertise in theoretical analysis can implement regression estimation and neural computing readily.
2018, 35(4):683-692.
DOI: 10.16356/j.1005-1120.2018.04.683
Abstract:
The paper is to integrate aerodynamic and aero-acoustic optimizatiom design of high lift devices, especially for two-element airfoils with slat. Aerodynamic analysis on flow field utilizes a high-order, high-resolution spatial differential method for large eddy simulation (LES), which can guarantee accuracy and efficiency. The aero-acoustic analysis for noise level is calculated with Ffowcs Williams-Hawkings (FW-H) integration formula. Fidelity of calculation is verified by standard models. Method of streamline-based Euler simulation (MSES) is used to obtain the aerodynamic characters. Based on the confirmation of numerical methods, detailed research has been conducted for the leading edge slat on multi-element airfoils. Various slot parameter influences on noise are analyzed.The results of the slot optimization parameters can be used in multi-element airfoil design.
The paper is to integrate aerodynamic and aero-acoustic optimizatiom design of high lift devices, especially for two-element airfoils with slat. Aerodynamic analysis on flow field utilizes a high-order, high-resolution spatial differential method for large eddy simulation (LES), which can guarantee accuracy and efficiency. The aero-acoustic analysis for noise level is calculated with Ffowcs Williams-Hawkings (FW-H) integration formula. Fidelity of calculation is verified by standard models. Method of streamline-based Euler simulation (MSES) is used to obtain the aerodynamic characters. Based on the confirmation of numerical methods, detailed research has been conducted for the leading edge slat on multi-element airfoils. Various slot parameter influences on noise are analyzed.The results of the slot optimization parameters can be used in multi-element airfoil design.
2018, 35(4):693-701.
DOI: 10.16356/j.1005-1120.2018.04.693
Abstract:
The command tracking problem of formation flight control system (FFCS) for multiple unmanned aerial vehicles (UAVs) with sensor faults is discussed. And the objective of the addressed control problem is to design a robust fault tolerant tracking controller such that, for the disturbances and sensor faults, the closed-loop system is asymptotically stable with a given disturbance attenuation level. A robust fault tolerant tracking control scheme, combining an observer with H∞ performance, is proposed. Furthermore, it is proved that the designed controller can guarantee asymptotic stability of FFCS despite sensor faults. Finally, a simulation of two UAV formations is employed to demonstrate the effectiveness of the proposed approach.
The command tracking problem of formation flight control system (FFCS) for multiple unmanned aerial vehicles (UAVs) with sensor faults is discussed. And the objective of the addressed control problem is to design a robust fault tolerant tracking controller such that, for the disturbances and sensor faults, the closed-loop system is asymptotically stable with a given disturbance attenuation level. A robust fault tolerant tracking control scheme, combining an observer with H∞ performance, is proposed. Furthermore, it is proved that the designed controller can guarantee asymptotic stability of FFCS despite sensor faults. Finally, a simulation of two UAV formations is employed to demonstrate the effectiveness of the proposed approach.
2018, 35(4):702-709.
DOI: 10.16356/j.1005-1120.2018.04.702
Abstract:
Magnetic field was introduced in laser melting deposition to reduce the pores in workpieces. Finite 3-D model of the coil-deposition layer-substrate was established. Simulation results show that the electromagnetic force in deposition layer mainly concentrates in the projection area of the coil. Axial electromagnetic force shows repulsion in one cycle. The experimental results indicate that the magnetic field is beneficial for grain refinement, microhardness increasement and decline of quantities and average sizes of pores.
Magnetic field was introduced in laser melting deposition to reduce the pores in workpieces. Finite 3-D model of the coil-deposition layer-substrate was established. Simulation results show that the electromagnetic force in deposition layer mainly concentrates in the projection area of the coil. Axial electromagnetic force shows repulsion in one cycle. The experimental results indicate that the magnetic field is beneficial for grain refinement, microhardness increasement and decline of quantities and average sizes of pores.
2018, 35(4):710-718.
DOI: 10.16356/j.1005-1120.2018.04.710
Abstract:
In the parametric modeling of the circuit model for glow discharge in air, a new method for the design of glow discharge circuit model is presented. The new circuit model is an important reference for the design of plasma power supply, the simulation of glow discharge plasma actuator and the simulation of glow discharge plasma anemometer. The modeling approach consists in developing an electrical model of the glow discharge in air based on circuit components. The structure of the circuit model is established according to the theoretical analysis and the experimental device. Then the parameters of the circuit model are obtained based on the circuit analysis. Finally, the circuit model is verified by comparing the simulation current with the experimental current. This model takes into account the whole framework of the air glow discharge including the sheath and the plasma area. The built circuit model is feasible and reliable, thus being instructive for the investigation of the glow discharge in air.
In the parametric modeling of the circuit model for glow discharge in air, a new method for the design of glow discharge circuit model is presented. The new circuit model is an important reference for the design of plasma power supply, the simulation of glow discharge plasma actuator and the simulation of glow discharge plasma anemometer. The modeling approach consists in developing an electrical model of the glow discharge in air based on circuit components. The structure of the circuit model is established according to the theoretical analysis and the experimental device. Then the parameters of the circuit model are obtained based on the circuit analysis. Finally, the circuit model is verified by comparing the simulation current with the experimental current. This model takes into account the whole framework of the air glow discharge including the sheath and the plasma area. The built circuit model is feasible and reliable, thus being instructive for the investigation of the glow discharge in air.
2018, 35(4):719-728.
DOI: 10.16356/j.1005-1120.2018.04.719
Abstract:
The uncertainty of the mechanism motion error is mostly caused by the manufacturing process, so the motion error cannot be effectively predicted at the design phase. The problems of manufacturing complexity and the relationship between design and manufacturing are analyzed, and the influence of dimensional tolerance and fit tolerance on the motion accuracy of the system is considered in the design process. Then based on the Monte Carlo simulation, an optimal design model of planar linkage mechanism is set up. A typical offset slider-crank mechanism is used as an illustrative example to carry out the optimal design. Compared with the result of typical robustness design, the similar variation characteristics of the mean value and the standard deviation can be found, so the proposed method is effective. The method is furthermore applied in the optimization of the schemes with different fit tolerances and the prediction of motion errors in the design phase is achieved. A set of quantitative evaluation system for mechanism optimal design is provided. Finally, a basic strategy is presented to balance the motion precision and manufacturing cost.
The uncertainty of the mechanism motion error is mostly caused by the manufacturing process, so the motion error cannot be effectively predicted at the design phase. The problems of manufacturing complexity and the relationship between design and manufacturing are analyzed, and the influence of dimensional tolerance and fit tolerance on the motion accuracy of the system is considered in the design process. Then based on the Monte Carlo simulation, an optimal design model of planar linkage mechanism is set up. A typical offset slider-crank mechanism is used as an illustrative example to carry out the optimal design. Compared with the result of typical robustness design, the similar variation characteristics of the mean value and the standard deviation can be found, so the proposed method is effective. The method is furthermore applied in the optimization of the schemes with different fit tolerances and the prediction of motion errors in the design phase is achieved. A set of quantitative evaluation system for mechanism optimal design is provided. Finally, a basic strategy is presented to balance the motion precision and manufacturing cost.
2018, 35(4):729-738.
DOI: 10.16356/j.1005-1120.2018.04.729
Abstract:
Automotive collision avoidance technology can effectively avoid the accidents caused by dangerous traffic conditions or driver's manipulation errors. Moreover, it can promote the development of autonomous driving for intelligent vehicle in intelligent transportation. We present a collision avoidance system, which is composed of an evasive trajectory planner and a path following controller. Considering the stability of the vehicle in the conflict-free process, the evasive trajectory planner is designed by polynomial parametric method and optimized by genetic algorithm. The path following controller is proposed to make the car drive along the designed path by controlling the vehicle's lateral movement. Simulation results show that the vehicle with the proposed controller has good stability in the collision process, and it can ensure the vehicle driving in accordance with the planned trajectory at different speeds. The research results can provide a certain basis for the research and development of automotive collision avoidance technology.
Automotive collision avoidance technology can effectively avoid the accidents caused by dangerous traffic conditions or driver's manipulation errors. Moreover, it can promote the development of autonomous driving for intelligent vehicle in intelligent transportation. We present a collision avoidance system, which is composed of an evasive trajectory planner and a path following controller. Considering the stability of the vehicle in the conflict-free process, the evasive trajectory planner is designed by polynomial parametric method and optimized by genetic algorithm. The path following controller is proposed to make the car drive along the designed path by controlling the vehicle's lateral movement. Simulation results show that the vehicle with the proposed controller has good stability in the collision process, and it can ensure the vehicle driving in accordance with the planned trajectory at different speeds. The research results can provide a certain basis for the research and development of automotive collision avoidance technology.
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