摘要 :
In order to solve the problems of time and angle control of the missile, such as the lack of information, and limited application conditions, an internal angle guidance law based on geometric relationship is proposed, with which t...
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In order to solve the problems of time and angle control of the missile, such as the lack of information, and limited application conditions, an internal angle guidance law based on geometric relationship is proposed, with which the control point is calculated by successive approximation. Supported by the guidance law, a feedforward and feedback compound guidance control scheme on the basis of the virtual target is designed. The simulation results have shown that the convergence speed is faster, the accuracy of time and angle control is much higher, and the calculation amount successfully meets the real-time requirements.
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摘要 :
In order to solve the problems of time and angle control of the missile, such as the lack of information, and limited application conditions, an internal angle guidance law based on geometric relationship is proposed, with which t...
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In order to solve the problems of time and angle control of the missile, such as the lack of information, and limited application conditions, an internal angle guidance law based on geometric relationship is proposed, with which the control point is calculated by successive approximation. Supported by the guidance law, a feedforward and feedback compound guidance control scheme on the basis of the virtual target is designed. The simulation results have shown that the convergence speed is faster, the accuracy of time and angle control is much higher, and the calculation amount successfully meets the real-time requirements.
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In order to enhance projectile kinetic energy, it is critical to increase bulk energy and progressivity of the propelling charge. Conventional ways to increase progressivity of gun propellant such as granular multi-perforation sha...
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In order to enhance projectile kinetic energy, it is critical to increase bulk energy and progressivity of the propelling charge. Conventional ways to increase progressivity of gun propellant such as granular multi-perforation shape or surface-coated treatment usually have limited loading density. Grain-molded propellant has high loading density and promising progressivity. Some gun propellant samples including grain-molded one have been made and their loading density and progressivity have been investigated in this paper. Results show that grain-molded gun propellant not only has high loading density but also has high progressivity. Adopting three-step process, e.g. grain surface-deterring firstly, surface-coating secondly and then grain-molding, can increase progressivity of grain-molded gun propellant greatly. Tests show that larger Pr will result in more propellant mass weight and higher muzzle velocity without exceeding pressure limit. A new index Pr based on closed-bomb test to evaluate progressively burning behavior is also introduced.
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摘要 :
In order to enhance projectile kinetic energy, it is critical to increase bulk energy and progressivity of the propelling charge. Conventional ways to increase progressivity of gun propellant such as granular multi-perforation sha...
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In order to enhance projectile kinetic energy, it is critical to increase bulk energy and progressivity of the propelling charge. Conventional ways to increase progressivity of gun propellant such as granular multi-perforation shape or surface-coated treatment usually have limited loading density. Grain-molded propellant has high loading density and promising progressivity. Some gun propellant samples including grain-molded one have been made and their loading density and progressivity have been investigated in this paper. Results show that grain-molded gun propellant not only has high loading density but also has high progressivity. Adopting three-step process, e.g. grain surface-deterring firstly, surface-coating secondly and then grain-molding, can increase progressivity of grain-molded gun propellant greatly. Tests show that larger Pr will result in more propellant mass weight and higher muzzle velocity without exceeding pressure limit. A new index Pr based on closed-bomb test to evaluate progressively burning behavior is also introduced.
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In today's big data era, the capability of analyze massive data efficient and return the results within an short time limit is critical to decision making, thus many big data system proposed and various distributed and parallel pr...
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In today's big data era, the capability of analyze massive data efficient and return the results within an short time limit is critical to decision making, thus many big data system proposed and various distributed and parallel processing techniques are heavily investigated. Among previous research, most of them are working on precise query processing, while approximate query processing (AQP) techniques which make interactive data exploration more efficiently and allows users to tradeoff between query accuracy and response time have not been investigate comprehensively. In this paper, we study the characteristics of aggregate query, a typical type of analytical query, and proposed an approximate query processing approach to optimize the execution of massive data based aggregate query with a histogram data structure. We implemented this approach into big data system Hive and compare it with Hive and AQP-enabled big data system BlinkDB, the experimental results verified that our approach is significantly fast than these existing systems in most scenarios.
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This paper brought up the assessment method of testability based on program structure which takes full account of invalidation mechanism of integrated information service platform software, and the we put forward the assessment pl...
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This paper brought up the assessment method of testability based on program structure which takes full account of invalidation mechanism of integrated information service platform software, and the we put forward the assessment plans in view of the control flow of the implementation of the software invalidation probability, the probability of infection status data and the probability of such programs as setting the value of variables -was quoted based on the state of the spread of infection data to the output, and the assessment method of software testability based on the three kinds of the data above is given. On the basis of which, software testability is evaluated.
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摘要 :
This paper brought up the assessment method of testability based on program structure which takes full account of invalidation mechanism of integrated information service platform software, and the we put forward the assessment pl...
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This paper brought up the assessment method of testability based on program structure which takes full account of invalidation mechanism of integrated information service platform software, and the we put forward the assessment plans in view of the control flow of the implementation of the software invalidation probability, the probability of infection status data and the probability of such programs as setting the value of variables -was quoted based on the state of the spread of infection data to the output, and the assessment method of software testability based on the three kinds of the data above is given. On the basis of which, software testability is evaluated.
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Amorphous Si{sub}3N{sub}4, Si/N/C and crystalline SiC nano-powders, 5-50 nm in mean diameter, with yields of 250 g/h were synthesized via laser induced gas phase reactions flow cost hexamethyldisilazane (HMDS)and NH{sub}3(or H{sub...
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Amorphous Si{sub}3N{sub}4, Si/N/C and crystalline SiC nano-powders, 5-50 nm in mean diameter, with yields of 250 g/h were synthesized via laser induced gas phase reactions flow cost hexamethyldisilazane (HMDS)and NH{sub}3(or H{sub}2).Reactionflame temperatures, which were controlled by the total gas flow rate, greatly influenced powder composition and crystallinity. Amorphous Si{sub}3N{sub}4 powders (96wt%) were obtained at l000℃ flow HMDS+NH{sub}3; β-SiC (93wt%) was formed at 1600℃ withH{sub}2. Amorphous Si/N/C powders with various N/C ratios (0.1-6) were synthesized at various temperatures. The main impurities in the powders were the organo-ligands such as NH{sub}x and CH{sub}x (X= 1-3) whose existence also resulted in a strong surface absorption of oxygen. Commercial production technologies of above mentioned powders were also stated.
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Abstract: Amorphous Si$-3$/N$-4$/, Si/N/C and crystalline SiC nano- powders, 5 - 50 nm in mean diameter, with yields of 250 g/h were synthesized via laser induced gas phase reactions flow cost hexamethyl...
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Abstract: Amorphous Si$-3$/N$-4$/, Si/N/C and crystalline SiC nano- powders, 5 - 50 nm in mean diameter, with yields of 250 g/h were synthesized via laser induced gas phase reactions flow cost hexamethyldisilazane (HMDS) and NH$-3$/ (or H$-2$/). Reaction flame temperatures, which were controlled by the total gas flow rate, greatly influenced powder composition and crystallinity. Amorphous Si$-3$/N$-4$/ powders (96 wt%) were obtained at 1000 degrees Celsius flow HMDS $PLU NH$-3$/; $beta@-SiC (93 wt%) was formed at 1600 degrees Celsius with H$-2$/. Amorphous Si/N/C powders with various N/C ratios (0.1 - 6) were synthesized at various temperatures. The main impurities in the powders were the organo-ligands such as NH$- x$/ and CH$-x$/ (X equals 1 - 3) whose existence also resulted in a strong surface absorption of oxygen. Commercial production technologies of above mentioned powders were also stated. !21
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Foamed asphalt is the main means of achieving largescale road repairs. Small foam asphalt mixture mixers are necessary test equipment before the road construction process. To avoid serious injuries due to equipment failure, the st...
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Foamed asphalt is the main means of achieving largescale road repairs. Small foam asphalt mixture mixers are necessary test equipment before the road construction process. To avoid serious injuries due to equipment failure, the structural reliability of the mixer is analyzed using failure mode and effects analysis (FMEA) and fault tree analysis (FTA). Foamed asphalt is a metastable state product, and the mixer operation requires immediate and efficient operation, which results in a relatively complicated structure of the device. Potential faults are easily overlooked in reliability analyses of mixer systems. For FMEA, the familiarity proportionality coefficient should be introduced to ensure accurate ranking of the risk priority numbers and to reduce potential bias due to subjective evaluations by personnel. For FTA, the bottom event with the lowest probability of failure is removed while the bottom event with the smallest risk priority numbers and correlations are combined. The obtained FMEA table and structural fault tree model can improve the accuracy of the risk priority numbers, effectively reduce the workload of the reliability analysis, and obtain the structural reliability with less data.NomenclatureFoamed asphalt. Small foam asphalt mixture mixer. Risk priority number. Fault tree analysis. Failure mode and effects analysis. Reliability. The familiarity ratio coefficient of the scorer.
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