In the existing impact time control guidance (ITCG) laws for moving-targets, the effects of time-varying velocity caused by aerodynamics and gravity cannot be effectively con-sidered. Therefore, an ITCG with field-of-...In the existing impact time control guidance (ITCG) laws for moving-targets, the effects of time-varying velocity caused by aerodynamics and gravity cannot be effectively con-sidered. Therefore, an ITCG with field-of-view (FOV) constraints based on biased proportional navigation guidance (PNG) is developed in this paper. The remaining flight time (time-to-go) estimation method is derived considering aerodynamic force and gravity. The number of differential equations is reduced and the integration step is increased by changing the integral variable, which makes it possible to obtain time-to-go through integration. An impact time controller with FOV constraints is proposed by analyzing the influence of the biased term on time-to-go and FOV constraint. Then, numerical simulations are performed to verify the correctness and superiority of the method.展开更多
A localized parametric time-sheared Gabor atom is derived by convolving a linear frequency modulated factor, modulating in frequency and translating in time to a dilated Gaussian function, which is the generalization ...A localized parametric time-sheared Gabor atom is derived by convolving a linear frequency modulated factor, modulating in frequency and translating in time to a dilated Gaussian function, which is the generalization of Gabor atom and is more delicate for matching most of the signals encountered in practice, especially for those having frequency dispersion characteristics. The time-frequency distribution of this atom concentrates in its time center and frequency center along energy curve, with the curve being oblique to a certain extent along the time axis. A novel parametric adaptive time-frequency distribution based on a set of the derived atoms is then proposed using a adaptive signal subspace decomposition method in frequency domain, which is non-negative time-frequency energy distribution and free of cross-term interference for multicomponent signals. The results of numerical simulation manifest the effectiveness of the approach in time-frequency representation and signal de-noising processing.展开更多
近年来,科研论文的合著现象及其与论文影响力之间的关系受到广泛关注。本文以1997—2013年Financial Times TOP 45商学院国际期刊论文为研究对象,对作者数量与论文被引(高被引还是零被引)之间的关系进行实证研究,从论文影响力方面揭示...近年来,科研论文的合著现象及其与论文影响力之间的关系受到广泛关注。本文以1997—2013年Financial Times TOP 45商学院国际期刊论文为研究对象,对作者数量与论文被引(高被引还是零被引)之间的关系进行实证研究,从论文影响力方面揭示商学领域是否存在最佳科研合作规模。研究发现:①与单独作者相比,多作者合作对论文总被引频次具有显著的正向影响,而且多作者合作论文成为高被引的概率更高,而成为零被引的概率更低;②作者数量与论文总被引频次之间存在显著的倒U形关系;进一步研究发现,作者数量与高被引论文概率呈倒U形关系,而与零被引论文概率呈正U形关系,且转折点均约为3人,表明商学领域存在使论文成为高被引而避免成为零被引的最佳合作规模;③分时间阶段实证结果表明,基于高被引和零被引的论文最佳合作规模逐步由2~3人增加至3~4人。展开更多
[目的]为转基因番茄植株的高通量筛选奠定基础。[方法]利用CTAB法提取番茄叶片总RNA进行Real Time PCR扩增，分析转MI1、2基因的番茄植株表达水平的检测体系。[结果]提取RNA的A260／A280为1．78～1．88，RNA无明显降解。在严谨扩增条件...[目的]为转基因番茄植株的高通量筛选奠定基础。[方法]利用CTAB法提取番茄叶片总RNA进行Real Time PCR扩增，分析转MI1、2基因的番茄植株表达水平的检测体系。[结果]提取RNA的A260／A280为1．78～1．88，RNA无明显降解。在严谨扩增条件下，引物SYBR2的扩增效率高于SYBR1。Mg^2＋的适宜浓度为2．0mg／L。Real Time PCR扩增产物具有良好的特异性，熔解曲线特异峰出现在84．5℃附近，在熔解曲线略低于83℃附近有极微弱的非特异峰。因此在定量反应中信号检测步骤应放在84℃。以4种不同模板分子数条件下扩增曲线Ct值得到的回归方程为Y=-3．78×log（copynumber）＋39．50，相关系数为0．998。[结论]该试验获得的Real Time PCR体系可用于转基因植株表达水平的检测。展开更多
GM管广泛应用于辐射测量,由于传统的测量方法受到GM管死时间的影响,其测量精度不高。介绍了没有死时间影响,可以提高测量精度的T im e-to-Coun t技术的测量方法,并从理论上论证了采用该方法的数学原理,在此基础上,提出对辐射强度的新估...GM管广泛应用于辐射测量,由于传统的测量方法受到GM管死时间的影响,其测量精度不高。介绍了没有死时间影响,可以提高测量精度的T im e-to-Coun t技术的测量方法,并从理论上论证了采用该方法的数学原理,在此基础上,提出对辐射强度的新估计式,并证明该估计是无偏的渐近最优的,是形式中最优的。并通过计算机仿真证明了该方法的正确性。展开更多
基金supported by the National Natural Science Foundation of China(U21B2028).
文摘In the existing impact time control guidance (ITCG) laws for moving-targets, the effects of time-varying velocity caused by aerodynamics and gravity cannot be effectively con-sidered. Therefore, an ITCG with field-of-view (FOV) constraints based on biased proportional navigation guidance (PNG) is developed in this paper. The remaining flight time (time-to-go) estimation method is derived considering aerodynamic force and gravity. The number of differential equations is reduced and the integration step is increased by changing the integral variable, which makes it possible to obtain time-to-go through integration. An impact time controller with FOV constraints is proposed by analyzing the influence of the biased term on time-to-go and FOV constraint. Then, numerical simulations are performed to verify the correctness and superiority of the method.
基金This project was supported by the National Natural Science Foundation of China (60472102)Shanghai Leading Academic Discipline Project (T0103).
文摘A localized parametric time-sheared Gabor atom is derived by convolving a linear frequency modulated factor, modulating in frequency and translating in time to a dilated Gaussian function, which is the generalization of Gabor atom and is more delicate for matching most of the signals encountered in practice, especially for those having frequency dispersion characteristics. The time-frequency distribution of this atom concentrates in its time center and frequency center along energy curve, with the curve being oblique to a certain extent along the time axis. A novel parametric adaptive time-frequency distribution based on a set of the derived atoms is then proposed using a adaptive signal subspace decomposition method in frequency domain, which is non-negative time-frequency energy distribution and free of cross-term interference for multicomponent signals. The results of numerical simulation manifest the effectiveness of the approach in time-frequency representation and signal de-noising processing.
文摘近年来,科研论文的合著现象及其与论文影响力之间的关系受到广泛关注。本文以1997—2013年Financial Times TOP 45商学院国际期刊论文为研究对象,对作者数量与论文被引(高被引还是零被引)之间的关系进行实证研究,从论文影响力方面揭示商学领域是否存在最佳科研合作规模。研究发现:①与单独作者相比,多作者合作对论文总被引频次具有显著的正向影响,而且多作者合作论文成为高被引的概率更高,而成为零被引的概率更低;②作者数量与论文总被引频次之间存在显著的倒U形关系;进一步研究发现,作者数量与高被引论文概率呈倒U形关系,而与零被引论文概率呈正U形关系,且转折点均约为3人,表明商学领域存在使论文成为高被引而避免成为零被引的最佳合作规模;③分时间阶段实证结果表明,基于高被引和零被引的论文最佳合作规模逐步由2~3人增加至3~4人。
文摘[目的]为转基因番茄植株的高通量筛选奠定基础。[方法]利用CTAB法提取番茄叶片总RNA进行Real Time PCR扩增，分析转MI1、2基因的番茄植株表达水平的检测体系。[结果]提取RNA的A260／A280为1．78～1．88，RNA无明显降解。在严谨扩增条件下，引物SYBR2的扩增效率高于SYBR1。Mg^2＋的适宜浓度为2．0mg／L。Real Time PCR扩增产物具有良好的特异性，熔解曲线特异峰出现在84．5℃附近，在熔解曲线略低于83℃附近有极微弱的非特异峰。因此在定量反应中信号检测步骤应放在84℃。以4种不同模板分子数条件下扩增曲线Ct值得到的回归方程为Y=-3．78×log（copynumber）＋39．50，相关系数为0．998。[结论]该试验获得的Real Time PCR体系可用于转基因植株表达水平的检测。
文摘GM管广泛应用于辐射测量,由于传统的测量方法受到GM管死时间的影响,其测量精度不高。介绍了没有死时间影响,可以提高测量精度的T im e-to-Coun t技术的测量方法,并从理论上论证了采用该方法的数学原理,在此基础上,提出对辐射强度的新估计式,并证明该估计是无偏的渐近最优的,是形式中最优的。并通过计算机仿真证明了该方法的正确性。
