The reliability of electromechanical product is usually determined by the fault number and working time traditionally. The shortcoming of this method is that the product must be in service. To design and enhance the r...The reliability of electromechanical product is usually determined by the fault number and working time traditionally. The shortcoming of this method is that the product must be in service. To design and enhance the reliability of the electromechanical product, the reliability evaluation method must be feasible and correct. Reliability evaluation method and algorithm were proposed. The reliability of product can be calculated by the reliability of subsystems which can be gained by experiment or historical data. The reliability of the machining center was evaluated by the method and algorithm as one example. The calculation result shows that the solution accuracy of mean time between failures is 97.4% calculated by the method proposed in this article compared by the traditional method. The method and algorithm can be used to evaluate the reliability of electromechanical product before it is in service.展开更多
The HOPping Field Emission Display （HOPFED） is a new architecture for field emission displays. The main difference between a conventional Field Emission Display （FED） device and a ItOPFED lies in the spacer struct...The HOPping Field Emission Display （HOPFED） is a new architecture for field emission displays. The main difference between a conventional Field Emission Display （FED） device and a ItOPFED lies in the spacer structure. In a HOPFED, two dielectric plates, named hop and flu spacer, are sandwiched between the emitter and the front plate. The objective of this spacer structure is to improve the performance oF a FED substantially with notable contrast, color purity and luminance uniformity. In order to optimize the structure of the device and to make the electron spot on the screen match the requirement of the phosphor dot dimension, the influence of electrical and structural parameters of the device on the electron spot profile was studied by numerical simulation in this paper. Monte Carlo method was employed to calculate the potential distribution inside hop and flu spacers due to secondary electrons mechanism plays an important role in HOPFED. The results indicated that the potential distribution in the spacers and spot profile depended strongly on the hop voltage, anode voltage and spacer＇s layout. This study may provide a useful theoretical support for optimizing the structure in HOPFED.展开更多
For civil structures founded on shallow foundations, the ground underneath the foundation often holds the greatest risks of the total structure. This can be due to of a very soft soil layer, an inhomogeneous subsurfac...For civil structures founded on shallow foundations, the ground underneath the foundation often holds the greatest risks of the total structure. This can be due to of a very soft soil layer, an inhomogeneous subsurface or a hidden dangerous object. It would be most favorable when a cheap and quick kind of seismic ＂tap-and-listen＂ technique can be used to detect those risks. The problem is however that an applied pulse or blast always creates a combination of compression-, shear- and surface-waves. These types of waves have different wave velocities and will return therefore at different time intervals. For a shallow subsurface technique, all these waves will overlap, which makes the interpretation very hard. Both the single pulse technique and the single-frequency, multiple wave technique （constant vibration） have been studied, but both techniques have their limitations. It can be concluded from finite element calculations that it will be difficult or even impossible to design good seismic techniques for surveying the underground of shallow foundations for hidden shallow potholes, etc.. The main reason is that the relative amount still present original wave. objects like water pipelines, undetonated bombs, dead bodies, coffins, of reflected energy is simply too low in comparison to the energy of the展开更多
It is known that a strictly piecewise monotone function with nonmonotonicity height ≥ 2 on a compact interval has no iterative roots of order greater than the number of forts. An open question is: Does it have iterat...It is known that a strictly piecewise monotone function with nonmonotonicity height ≥ 2 on a compact interval has no iterative roots of order greater than the number of forts. An open question is: Does it have iterative roots of order less than or equal to the number of forts? An answer was given recently in the case of "equal to". Since many theories of resultant and algebraic varieties can be applied to computation of polynomials, a special class of strictly piecewise monotone functions, in this paper we investigate the question in the case of "less than" for polynomials. For this purpose we extend the question from a compact interval to the whole real line and give a procedure of computation for real polynomial iterative roots. Applying the procedure together with the theory of discriminants, we find all real quartic polynomials of non-monotonicity height 2 which have quadratic polynomial iterative roots of order 2 and answer the question.展开更多
基金Project(2013ZX04013047)supported by the Major Program of National Natural Science Foundation of ChinaProject(51275014)supported by the National Natural Science Foundation of China
文摘The reliability of electromechanical product is usually determined by the fault number and working time traditionally. The shortcoming of this method is that the product must be in service. To design and enhance the reliability of the electromechanical product, the reliability evaluation method must be feasible and correct. Reliability evaluation method and algorithm were proposed. The reliability of product can be calculated by the reliability of subsystems which can be gained by experiment or historical data. The reliability of the machining center was evaluated by the method and algorithm as one example. The calculation result shows that the solution accuracy of mean time between failures is 97.4% calculated by the method proposed in this article compared by the traditional method. The method and algorithm can be used to evaluate the reliability of electromechanical product before it is in service.
文摘The HOPping Field Emission Display （HOPFED） is a new architecture for field emission displays. The main difference between a conventional Field Emission Display （FED） device and a ItOPFED lies in the spacer structure. In a HOPFED, two dielectric plates, named hop and flu spacer, are sandwiched between the emitter and the front plate. The objective of this spacer structure is to improve the performance oF a FED substantially with notable contrast, color purity and luminance uniformity. In order to optimize the structure of the device and to make the electron spot on the screen match the requirement of the phosphor dot dimension, the influence of electrical and structural parameters of the device on the electron spot profile was studied by numerical simulation in this paper. Monte Carlo method was employed to calculate the potential distribution inside hop and flu spacers due to secondary electrons mechanism plays an important role in HOPFED. The results indicated that the potential distribution in the spacers and spot profile depended strongly on the hop voltage, anode voltage and spacer＇s layout. This study may provide a useful theoretical support for optimizing the structure in HOPFED.
文摘For civil structures founded on shallow foundations, the ground underneath the foundation often holds the greatest risks of the total structure. This can be due to of a very soft soil layer, an inhomogeneous subsurface or a hidden dangerous object. It would be most favorable when a cheap and quick kind of seismic ＂tap-and-listen＂ technique can be used to detect those risks. The problem is however that an applied pulse or blast always creates a combination of compression-, shear- and surface-waves. These types of waves have different wave velocities and will return therefore at different time intervals. For a shallow subsurface technique, all these waves will overlap, which makes the interpretation very hard. Both the single pulse technique and the single-frequency, multiple wave technique （constant vibration） have been studied, but both techniques have their limitations. It can be concluded from finite element calculations that it will be difficult or even impossible to design good seismic techniques for surveying the underground of shallow foundations for hidden shallow potholes, etc.. The main reason is that the relative amount still present original wave. objects like water pipelines, undetonated bombs, dead bodies, coffins, of reflected energy is simply too low in comparison to the energy of the
基金supported by the National Basic Research Program of China (Grant No. 2011CB302402)National Natural Science Foundation of China (Grant Nos. 61021004 and 10825104)Shanghai Leading Academic Discipline Project (Grant No. B412)
文摘It is known that a strictly piecewise monotone function with nonmonotonicity height ≥ 2 on a compact interval has no iterative roots of order greater than the number of forts. An open question is: Does it have iterative roots of order less than or equal to the number of forts? An answer was given recently in the case of "equal to". Since many theories of resultant and algebraic varieties can be applied to computation of polynomials, a special class of strictly piecewise monotone functions, in this paper we investigate the question in the case of "less than" for polynomials. For this purpose we extend the question from a compact interval to the whole real line and give a procedure of computation for real polynomial iterative roots. Applying the procedure together with the theory of discriminants, we find all real quartic polynomials of non-monotonicity height 2 which have quadratic polynomial iterative roots of order 2 and answer the question.
