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For traditional linear Stirling Cryocoolers, the amplitude of output sinusoidal AC voltage is modulated mainly by Modulation ratio (M) controlled by the inverter, so that the compression piston is driven to perform linear reciproc...
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For traditional linear Stirling Cryocoolers, the amplitude of output sinusoidal AC voltage is modulated mainly by Modulation ratio (M) controlled by the inverter, so that the compression piston is driven to perform linear reciprocating motion and the compressed refrigerant expands rapidly in the expander to achieve the purpose of refrigeration. In practice, however, when M is used to modulate the amplitude of sinusoidal AC voltage, the input power and current will increase to a certain extent with the decreased M. To address the aforementioned concern, the correlated characteristics of output voltage of the inverter under the M and vector phase shift modes will be compared and analyzed in this paper for the selection of best driving mode for linear Stirling cryocoolers. Although the experiments reveal a small difference of sinusoidal voltage amplitude of the two modes under the same input voltage, and a basically same energy distribution of waveform at the fundamental frequency and other frequency multiplications, the required power and current are more stable and do not increase with the decreased output voltage amplitude in the mode of vector phase shift.
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In this paper, a wing weight estimation method for transport aircraft is presented. By establishing related computational framework, a wing-box model is developed based on wing-box beam design, from where a wing weight estimation ...
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In this paper, a wing weight estimation method for transport aircraft is presented. By establishing related computational framework, a wing-box model is developed based on wing-box beam design, from where a wing weight estimation method is derived. The key steps of this work include parametric modeling based on structural model simplification, aerodynamic study, finite element method, and aeroeiastic analysis. The influence of the mounted pylon has been considered for the wing-box sizing. This method has been validated using data of two different transport aircrafts. which shows that this method is robust and efficient. Outcome of this paper could be rapidly integrated in the conceptual design phase.
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This paper discusses the orbits design of coordinated monitoring system for lunar transfer vehicles. The feature of direct lunar transfer, invariant manifold transfer and gravity-assist transfer are analyzed. An optimization model...
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This paper discusses the orbits design of coordinated monitoring system for lunar transfer vehicles. The feature of direct lunar transfer, invariant manifold transfer and gravity-assist transfer are analyzed. An optimization model are established. The objective function of model are the probability of finding lunar transfer vehicles, the probability of continued tracking and covering rate of moon region. A monitoring strategy using synodic month period orbit is proposed. Solving the optimization model and the design of monitoring system for lunar transfer vehicles is obtained. The design arrange satellites in short period orbits of L4 and L5 and vertical orbit in L3 respectively. The designed monitoring system has good optics conditions and observe distance. The probabilities of finding lunar transfer vehicles, the probability of continued tracking and covering rate of moon region are 89%, 87% and 96%.
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This paper focuses on the problem of designing a large 256*256 high-performance broadband packet (or ATM) switch. Early packet switch research concentrated on using N*Log_2N structures with buffers at each switch element. As a res...
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This paper focuses on the problem of designing a large 256*256 high-performance broadband packet (or ATM) switch. Early packet switch research concentrated on using N*Log_2N structures with buffers at each switch element. As a result, the nude number and the cost of such kinds of switches become prodigious and consequently could not have more practical significance. In this paper, we provide a method to design a kind of architecture containing fewer nodes. The distribution network of this new architecture based on the knockout theory has very low internal blocking, similar to that found in large 256*56 single crossbar networks, but the complexity and cost are less than that of single crossbar networks. A Balanced Incomplete Block Design (BIBD) in Combinatorics is provided to help construct the architecture. With this method, the mapping function between the input ports and the crossbars can be realized by a serial of mutually orthogonal Latin Squares (MOLS). Moreover, statistical tools are used to calculate the possibility of internal blocking of the network and to make a comparison between the improved architecture and the common one.
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摘要 :
This paper focuses on the problem of designing a large 256 x 256 high-performance broadband packet (or ATM) switch. Early packet switch research concentrated on using Nx log_2N structures with buffers at each switch element. As a ...
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This paper focuses on the problem of designing a large 256 x 256 high-performance broadband packet (or ATM) switch. Early packet switch research concentrated on using Nx log_2N structures with buffers at each switch element. As a result, the nude number and the cost of such kinds of switches become prodigious and consequently could not have more practical significance. In this paper, we provide a method to design a kind of architecture containing fewer nodes. The distribution network of this new architecture based on the knockout theory has very low internal blocking, similar to that found in large 256 x 256 single crossbar networks, but the complexity and cost are less than that of single crossbar networks. A Balanced Incomplete Block Design (BIBD) in Combinatorics is provided to help construct the architecture. With this method, the mapping function between the input ports and the crossbars can be realized by a serial of mutually orthogonal Latin Squares (MOLS). Moreover, statistical tools are used to calculate the possibility of internal blocking of the network and to make a comparison between the improved architecture and the common one.
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The unsteady aerodynamic characteristics for a slender revolution under the influence of pitching oscillation at high angle of attack were simulated numerically using DES (Detached-Eddy Simulation) approach. The numerical results ...
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The unsteady aerodynamic characteristics for a slender revolution under the influence of pitching oscillation at high angle of attack were simulated numerically using DES (Detached-Eddy Simulation) approach. The numerical results show that the DES model is more suitable for the complex separated flow around the slender body at extremely high angle of attack. Based on DES methods, the location and strength of separated vortex, flow field, pressure distribution on the surface and force coefficients were observed and analyzed. It is found that, the pitching oscillation has strong control ability to the asymmetric separated vortex around slender body, and it would change the construction of flow field, the asymmetrical flow was restrained and tends to symmetrical flow.
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摘要 :
The unsteady aerodynamic characteristics for a slender revolution under the influence of pitching oscillation at high angle of attack were simulated numerically using DES (Detached-Eddy Simulation) approach. The numerical results ...
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The unsteady aerodynamic characteristics for a slender revolution under the influence of pitching oscillation at high angle of attack were simulated numerically using DES (Detached-Eddy Simulation) approach. The numerical results show that the DES model is more suitable for the complex separated flow around the slender body at extremely high angle of attack. Based on DES methods, the location and strength of separated vortex, flow field, pressure distribution on the surface and force coefficients were observed and analyzed. It is found that, the pitching oscillation has strong control ability to the asymmetric separated vortex around slender body, and it would change the construction of flow field, the asymmetrical flow was restrained and tends to symmetrical flow.
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摘要 :
The unsteady aerodynamic characteristics for a slender revolution under the influence of pitching oscillation at high angle of attack were simulated numerically using DES (Detached-Eddy Simulation) approach. The numerical results ...
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The unsteady aerodynamic characteristics for a slender revolution under the influence of pitching oscillation at high angle of attack were simulated numerically using DES (Detached-Eddy Simulation) approach. The numerical results show that the DES model is more suitable for the complex separated flow around the slender body at extremely high angle of attack. Based on DES methods, the location and strength of separated vortex, flow field, pressure distribution on the surface and force coefficients were observed and analyzed. It is found that, the pitching oscillation has strong control ability to the asymmetric separated vortex around slender body, and it would change the construction of flow field, the asymmetrical flow was restrained and tends to symmetrical flow.
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Using the techniques of X-ray imaging and analysis of P-T and P-H curves, we study the characteristics of jet penetration of multilayer titanium-corunduM ceramic and the mechanisms of titanium-corunduM ceramic to resist jet penetr...
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Using the techniques of X-ray imaging and analysis of P-T and P-H curves, we study the characteristics of jet penetration of multilayer titanium-corunduM ceramic and the mechanisms of titanium-corunduM ceramic to resist jet penetration. We determine the P-T and P-H curves with differential elements of jet against titanium-corundum ceramic and 45 steel. The results show that, for high speed jet penetration, the anti-jet penetration capability of 45 steel is greater than that of the ceramic. For medium and low speed jet penetration, the anti-jet penetration capability of the ceramic is greater than that of 45 steel. For all stand-off conditions studied, the DOP of the ceramic target is less than the DOP of 45 steel. This indicates that the anti-jet penetration capability of the ceramic is better than the same thickness of 45 steel. The P-T and P-H technique allows the direct observation of jet elements penetrating the target plate.
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摘要 :
Using the techniques of X-ray imaging and analysis of P-T and P-H curves, we study the characteristics of jet penetration of multilayer titanium-corunduM ceramic and the mechanisms of titanium-corunduM ceramic to resist jet penetr...
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Using the techniques of X-ray imaging and analysis of P-T and P-H curves, we study the characteristics of jet penetration of multilayer titanium-corunduM ceramic and the mechanisms of titanium-corunduM ceramic to resist jet penetration. We determine the P-T and P-H curves with differential elements of jet against titanium-corundum ceramic and 45 steel. The results show that, for high speed jet penetration, the anti-jet penetration capability of 45 steel is greater than that of the ceramic. For medium and low speed jet penetration, the anti-jet penetration capability of the ceramic is greater than that of 45 steel. For all stand-off conditions studied, the DOP of the ceramic target is less than the DOP of 45 steel. This indicates that the anti-jet penetration capability of the ceramic is better than the same thickness of 45 steel. The P-T and P-H technique allows the direct observation of jet elements penetrating the target plate.
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